Reidar Haugsrud

• Dayaghi, Amir Masoud; Polfus, Jonathan M.; Strandbakke, Ragnar; Pokle, Anuj; Almar, Laura & Escolastico, Sonia [Show all 10 contributors for this article] (2023). Effects of sintering additives on defect chemistry and hydration of BaZr0.4Ce0.4(Y,Yb)0.2O3−δ proton conducting electrolytes. Solid State Ionics. ISSN 0167-2738. 401. doi: 10.1016/j.ssi.2023.116355.
• Li, Zuoan & Haugsrud, Reidar (2023). Surface kinetics and bulk transport in La2Ni0.5Cu0.5O4+δ membranes from conductivity relaxation. Journal of the European Ceramic Society. ISSN 0955-2219. 43(2), p. 462–467. doi: 10.1016/j.jeurceramsoc.2022.10.046. Full text in Research Archive Show summary

  This work reports conductivity relaxation measurements on both uncoated (1.2 mm thick) and coated (2.0 mm thick) La2Ni0.5Cu0.5O4+δ membranes in the temperature range between 550-850 °C and oxygen partial pressures from 0.01 to 1.0 atm. The results show that surface kinetics has a significant effect on the relaxation profiles, especially at low temperatures and should not be neglected when extracting transport parameters. Oxygen chemical diffusion and surface exchange coefficients have been determined by transient conductivity with surface modification. Higher activation energy of surface exchange compared to bulk diffusion is observed in La2Ni0.5Cu0.5O4+δ, similar to that in La2NiO4+δ. Based on the oxygen partial pressure dependence of the surface exchange coefficient, it has been revealed that oxygen dissociative adsorption rate-limits the surface exchange.

• Emhjellen, Linn Katinka Susanne Shi; Liu, Xin; Polfus, Jonathan M. & Haugsrud, Reidar (2022). Native point defects and polaron transport in zirconium pyrovanadate. Solid State Ionics. ISSN 0167-2738. 386, p. 1–8. doi: 10.1016/j.ssi.2022.116033.
• Emhjellen, Linn Katinka Susanne Shi; Xing, Wen; Li, Zuoan & Haugsrud, Reidar (2022). Oxygen permeability and surface kinetics of composite oxygen transport membranes based on stabilized δ-Bi2O3. Journal of Membrane Science. ISSN 0376-7388. 660, p. 1–6. doi: 10.1016/j.memsci.2022.120875. Full text in Research Archive
• Emhjellen, Linn Katinka Susanne Shi; Strandbakke, Ragnar & Haugsrud, Reidar (2021). Electrical transport in a molten-solid V2O5–ZrV2O7 composite. Journal of Materials Chemistry A. ISSN 2050-7488. 9(34), p. 18537–18545. doi: 10.1039/D1TA03750A. Full text in Research Archive
• Hasle, Ida; Waldow, Stephan P.; Gries, Ute N.; De Souza, Roger A.; Vøllestad, Einar & Haugsrud, Reidar (2021). B-site cation inter-diffusion in yttrium substituted barium zirconate. Journal of Materials Chemistry A. ISSN 2050-7488. 9(37), p. 21142–21150. doi: 10.1039/d1ta02391h. Full text in Research Archive Show summary

  B-site cation inter-diffusion in the ABO3 perovskite yttrium-substituted barium zirconate (BZY) was studied at temperatures from 1100 to 1460 °C under reducing and oxidising conditions. The experiments followed two different approaches using Ce as a chemical tracer for Zr. By fitting diffusion profiles of the cation obtained by either Electron Probe Microanalysis (EPMA) or Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), we determined bulk, grain-boundary and effective diffusion coefficients. The activation energies of bulk diffusion (4.5 ± 0.4 eV) are similar to the migration enthalpy obtained by a computational approach (∼4 eV). On this basis, we conclude that the activation energies correspond to the migration enthalpies, assuming that the concentration of Zr vacancies in the bulk was frozen-in. Grain-boundary diffusion coefficients were found to be more than four orders of magnitude higher than the corresponding bulk values, while the activation energies of grain-boundary diffusion are relatively similar to those for bulk. This was attributed to higher concentrations of cation vacancies in space-charge layers at the boundaries. Overall, the results show that BZY electrolytes are highly stable towards degradation related to B-site cation diffusion.

• Dayaghi, Amir Masoud; Haugsrud, Reidar; Stange, Marit Synnøve Sæverud; Larring, Yngve; Strandbakke, Ragnar & Norby, Truls Eivind (2021). Increasing the thermal expansion of proton conducting Y-doped BaZrO3 by Sr and Ce substitution. Solid State Ionics. ISSN 0167-2738. 359. doi: 10.1016/j.ssi.2020.115534. Full text in Research Archive Show summary

  Proton conducting oxide electrolytes find potential application in proton ceramic fuel cells and electrolyzers operating at intermediate temperatures, e.g. 400–600 °C. However, state-of-the-art proton conducting ceramics based on Y-doped BaZrO3 (BZY) have lower thermal expansion coefficient (TEC) than most commonly applied or conceived supporting electrode structures, making the assembly vulnerable to degradation due to cracks or spallation. We have increased the TEC of 20 mol% Y-doped BZY (BZY20) by partially substituting Ba and Zr with Sr and Ce, respectively, to levels which still maintain the cubic structure and sufficiently minor n-type conduction; (Ba0.85Sr0.15)(Zr0.7Ce0.1Y0.2)O2.9 (BSZCY151020). High temperature XRD shows that this material has a cubic structure (space group ) in the temperature range of 25–1150 °C and a linear TEC of ~10 × 10−6 K−1, as compared to the ~8 × 10−6 K−1 for BZY. It exhibited a DC conductivity of ~5 mS cm−1 at 600 °C in wet H2. This electrolyte with increased TEC may find application in proton ceramic electrochemical cells in general and metal supported ones in particular.

• Kalland, Liv-Elisif Queseth; Løken, Andreas; Bjørheim, Tor Svendsen; Haugsrud, Reidar & Norby, Truls Eivind (2020). Structure, hydration, and proton conductivity in 50% La and Nd doped CeO2 – La2Ce2O7 and Nd2Ce2O7 – and their solid solutions. Solid State Ionics. ISSN 0167-2738. 354. doi: 10.1016/j.ssi.2020.115401. Full text in Research Archive
• Stefan, Elena; Denonville, Christelle; Larring, Yngve; Stange, Marit Synnøve Sæverud & Haugsrud, Reidar (2019). Oxidation study of porous metal substrates for metal supported proton ceramic electrolyzer cells. Corrosion Science. ISSN 0010-938X. 164. doi: 10.1016/j.corsci.2019.108335.
• Stange, Marit Synnøve Sæverud; Dayaghi, Amir Masoud; Denonville, Christelle; Larring, Yngve; Rørvik, Per Martin & Haugsrud, Reidar [Show all 7 contributors for this article] (2019). Fabrication of metal-supported proton-conducting electrolysers with thin film Sr- And Ce-doped BZY electrolyte. ECS Transactions. ISSN 1938-5862. 91(1), p. 941–949. doi: 10.1149/09101.0941ecst. Show summary

  n this work, we present fabrication and initial testing of metal-supported proton ceramic electrolyser (MS-PCEC) single cells with a thin electrolyte. Plansee ITM porous metal is used as metal support. Spray-coating is used to deposit a conducting layer of La1-xSrxTi1-yNiyO3-δ (LSTN) which is used for low temperature (600-800 °C) deposition of a gas-tight, thin-film layer (~2 μm) of electrolyte by pulsed laser deposition (PLD). Post-annealing of the electrolyte is evaluated to improve its performance. In order to have a smaller thermal expansion coefficient (TEC) mismatch towards LSTN (~10-11 × 10-6 K-1), we developed a new Sr- and Ce-doped proton-conducting electrolyte, yielding a larger TEC (~10-11 × 10-6 K-1) compared to BZY (~8 × 10-6 K-1). The cell with Pt as air electrode shows acceptable open circuit voltage and low overpotentials at 600 °C, demonstrating the potential of developing the first working MS-PCEC.

• Liu, Xin; Bjørheim, Tor Svendsen; Vines, Lasse; Fjellvåg, Øystein; Granerød, Cecilie Skjold & Prytz, Øystein [Show all 10 contributors for this article] (2019). Highly Correlated Hydride Ion Tracer Diffusion in SrTiO3–xHx Oxyhydrides. Journal of the American Chemical Society. ISSN 0002-7863. 141(11), p. 4653–4659. doi: 10.1021/jacs.8b12985. Full text in Research Archive
• Liu, Xin; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2018). Formation of defects and their effects on hydride ion transport properties in a series of K2NiF4-type oxyhydrides. Journal of Materials Chemistry A. ISSN 2050-7488. 6(4), p. 1454–1461. doi: 10.1039/c7ta08435h.
• Desissa, Temesgen D.; Haugsrud, Reidar; Wiik, Kjell & Norby, Truls Eivind (2018). Inter-diffusion across a direct p-n heterojunction of Li-doped NiO and Al-doped ZnO. Solid State Ionics. ISSN 0167-2738. 320, p. 215–220. doi: 10.1016/j.ssi.2018.03.011. Full text in Research Archive Show summary

  We herein report inter-diffusion across the interface between p-type Ni0.98Li0.02O and n-type Zn0.98Al0.02O for various applications including p-n-heterojunction diodes and oxide thermoelectrics. Diffusion couples were made of polished surfaces of ceramic samples pre-sintered at 1250 and 1350 °C for Ni0.98Li0.02O and Zn0.98Al0.02O, respectively. The inter-diffusion couples were annealed at 900–1200 °C for 160 h in ambient air. Electron Probe Micro Analysis (EPMA) was used to acquire diffusion profiles, followed by fitting to Fick's second law and Whipple–Le Claire's models for bulk and grain-boundary diffusion calculation, respectively. Zn2+ diffused into Ni0.98Li0.02O mainly by bulk diffusion with an activation energy of 250 ± 10 kJ/mol, whereas Ni2+ diffused into Zn0.98Al0.02O by both bulk and enhanced grain boundary diffusion with activation energies of 320 ± 120 kJ/mol and 245 ± 50 kJ/mol, respectively. The amount of Al3+ diffused from the Al-doped ZnO into the NiO phase was too small for a corresponding diffusion coefficient to be calculated. Li-ion distribution and diffusivity were not determined due to lack of analyzer sensitivity for Li. The bulk and effective diffusivities of Zn2+ and Ni2+ into NiO and ZnO enable prediction of inter-diffusion lengths as a function of time and temperature, allowing estimates of device performance, stability, and lifetimes at different operation temperatures.

• Malerød-Fjeld, Harald; Clark, Daniel Ryan; Yuste-Tirados, Irene; Zanón, Raquel; Catalán-Martinez, David & Beeaff, Dustin [Show all 12 contributors for this article] (2017). Thermo-electrochemical production of compressed hydrogen from methane with near-zero energy loss. Nature Energy. ISSN 2058-7546. 2(12), p. 923–931. doi: 10.1038/s41560-017-0029-4.
• Escolastico, S; Solis, C; Haugsrud, Reidar; Magraso, Anna & Serra, J. M. (2017). On the ionic character of H2 separation through mixed conducting Nd5.5W0.5Mo0.5O11.25−δ membrane. International Journal of Hydrogen Energy. ISSN 0360-3199. 42(16), p. 11392–11399. doi: 10.1016/j.ijhydene.2017.02.087.
• Hancke, Ragnhild & Haugsrud, Reidar (2017). The correlation between surface kinetic and bulk diffusion properties of proton conducting oxides. Solid State Ionics. ISSN 0167-2738. 306, p. 48–54. doi: 10.1016/j.ssi.2017.02.006.
• Stange, Marit Synnøve Sæverud; Stefan, Elena; Denonville, Christelle; Larring, Yngve; Rørvik, Per Martin & Haugsrud, Reidar (2017). Development of novel metal-supported proton ceramic electrolyser cell with thin film BZY15–Ni electrode and BZY15 electrolyte. International Journal of Hydrogen Energy. ISSN 0360-3199. 42(19), p. 13454–13462. doi: 10.1016/j.ijhydene.2017.03.028. Full text in Research Archive
• Sazinas, Rokas; Sakaguchi, Isao; Hasle, Ida Margrete; Polfus, Jonathan M.; Haugsrud, Reidar & Einarsrud, Mari-Ann [Show all 7 contributors for this article] (2017). Tracer diffusion of 96Zr and 134Ba in polycrystalline BaZrO3. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 19(32), p. 21878–21886. doi: 10.1039/C7CP04039C. Full text in Research Archive
• Stefan, Elena; Stange, Marit Synnøve Sæverud; Denonville, Christelle; Larring, Yngve; Hildenbrand, Nicolas & Norby, Truls Eivind [Show all 7 contributors for this article] (2017). Layered microstructures based on BaZr0.85Y0.15O3−δ by pulsed laser deposition for metal-supported proton ceramic electrolyser cells. Journal of Materials Science. ISSN 0022-2461. 52(11), p. 6486–6497. doi: 10.1007/s10853-017-0884-1. Full text in Research Archive
• Liu, Xin; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2017). Formation and migration of hydride ions in BaTiO3-xHx oxyhydride. Journal of Materials Chemistry A. ISSN 2050-7488. 5(3), p. 1050–1056. doi: 10.1039/c6ta06611a.
• Cao, Yong; Duan, Nanqi; Jian, Li; Evans, Anna & Haugsrud, Reidar (2016). Effect of Nb Doping on Hydration and Conductivity of La27W5O55.5. Journal of The American Ceramic Society. ISSN 0002-7820. 99(10), p. 3309–3316. doi: 10.1111/jace.14346.
• Løken, Andreas; Haugsrud, Reidar & Bjørheim, Tor Svendsen (2016). Unravelling the fundamentals of thermal and chemical expansion of BaCeO3 from first principles phonon calculations. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 18(45), p. 31296–31303. doi: 10.1039/C6CP05710A. Full text in Research Archive
• Cao, Yong; Xiong, Chunyan; Jian, Li; Vøllestad, Einar; Evans, Anna & Haugsrud, Reidar (2016). Enhancement of the electron conductivity of La27(W0.85Nb0.15)5O55.5-δ by Mo doping for hydrogen permeation. Journal of the Electrochemical Society. ISSN 0013-4651. 163(10), p. F1151–F1156. doi: 10.1149/2.1251609jes.
• Wachowski, Sebastian Lech; Mielewczyk-Gryn, Aleksandra; Zagorski, Krzysztof; Li, Cheng; Jasinski, Piotr & Skinner, Stephen J [Show all 8 contributors for this article] (2016). Influence of Sb-substitution on ionic transport in lanthanum orthoniobates. Journal of Materials Chemistry A. ISSN 2050-7488. 4(30), p. 11696–11707. doi: 10.1039/c6ta03403a.
• Skomedal, Gunstein; Burkov, Alexander; Samunin, Alexander Yu; Haugsrud, Reidar & Middleton, Peter Hugh (2016). High temperature oxidation of Mg2(Si-Sn). Corrosion Science. ISSN 0010-938X. 111(1), p. 325–333. doi: 10.1016/j.corsci.2016.05.016.
• Liu, Xin; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2016). Thermochemical properties of rare-earth oxyhydrides from first principles phonon calculations. RSC Advances. ISSN 2046-2069. 6(12), p. 9822–9826. doi: 10.1039/c5ra26552e.
• Bjørheim, Tor Svendsen; Løken, Andreas & Haugsrud, Reidar (2016). On the relationship between chemical expansion and hydration thermodynamics of proton conducting perovskites. Journal of Materials Chemistry A. ISSN 2050-7488. 4(16), p. 5917–5924. doi: 10.1039/c5ta10090a. Full text in Research Archive
• Løken, Andreas; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2015). The pivotal role of the dopant choice on the thermodynamics of hydration and associations in proton conducting BaCe0.9X0.1O3-δ (X = Sc, Ga, Y, In, Gd and Er). Journal of Materials Chemistry A. ISSN 2050-7488. 3(46), p. 23289–23298. doi: 10.1039/c5ta04932f. Full text in Research Archive
• Magraso, Anna; Falk-Windisch, Hannes; Froitzheim, Jan; Svensson, Jan-Erik & Haugsrud, Reidar (2015). Reduced long term electrical resistance in Ce/Co-coated ferritic stainless steel for solid oxide fuel cell metallic interconnects. International Journal of Hydrogen Energy. ISSN 0360-3199. 40(27), p. 8579–8585. doi: 10.1016/j.ijhydene.2015.04.147.
• Bjørheim, Tor Svendsen & Haugsrud, Reidar (2015). Proton transport properties of the RE3Ga5MO14 (RE = La, Nd and M = Si, Ti, Sn) langasite family of oxides. Solid State Ionics. ISSN 0167-2738. 275, p. 29–34. doi: 10.1016/j.ssi.2015.03.014.
• Bjørheim, Tor Svendsen; Shanmugappirabu, Vijay; Haugsrud, Reidar & Norby, Truls (2015). Protons in piezoelectric langatate; La3Ga5.5Ta0.5O14. Solid State Ionics. ISSN 0167-2738. 278(1), p. 275–280. doi: 10.1016/j.ssi.2015.06.024.
• Ashok, Anuradha Machina; Haugsrud, Reidar; Norby, Truls & Olsen, Arne (2015). Structural study of the complex perovskite Ba4(Ba2Nb2)O11. Materials Characterization. ISSN 1044-5803. 102, p. 71–78. doi: 10.1016/j.matchar.2015.02.014.

View all works in Cristin

• Andersen, Håkon; Larring, Yngve & Haugsrud, Reidar (2024). Kinetic study of novel oxygen carriers for chemical looping for hydrogen production: Ca0.6La0.4Ti0.1CrxMn0.9-xO3-δ (x = 0.3, 0.45 & 0.6).
• Gudmundsdottir, Jonina Björg; Vøllestad, Einar; Haugsrud, Reidar & Polfus, Jonathan (2023). Oxygen Exchange Kinetics of BaGd0.3La0.7Co2O6-d.
• Andersen, Håkon; Larring, Yngve & Haugsrud, Reidar (2023). Particle size effects on pulse isotope exchange measurements.
• Thoreton, Vincent & Haugsrud, Reidar (2022). Surface Exchange Study of Proton Ceramic Electrochemical Cell’s Positrode by Gas Phase .
• Stange, Marit Synnøve Sæverud; Denonville, Christelle; Stefan, Elena; Dayaghi, Amir Masoud; Larring, Yngve & Rørvik, Per Martin [Show all 9 contributors for this article] (2022). Fabrication and testing of thin-film based metal-supported proton ceramic electrochemical cells.
• Xing, Wen; Emhjellen, Linn Katinka Susanne Shi; Haugsrud, Reidar & Li, Zuoan (2022). Ceramic composite oxygen transport membranes based on stabilised Bi2O3.
• Dayaghi, Amir Masoud; Polfus, Jonathan; Strandbakke, Ragnar; Vøllestad, Einar; Haugsrud, Reidar & Norby, Truls (2022). Effects of NiO, ZnO and CuO sintering additives on the hydration of BaZr0.4Ce0.4(Y,Yb)0.2O3-δ proton conducting electrolytes.
• Stange, Marit Synnøve Sæverud; Stefan, Elena; Dayaghi, Amir Masoud; Denonville, Christelle; Larring, Yngve & Rørvik, Per Martin [Show all 8 contributors for this article] (2021). Pulsed Laser Deposition of Electrolytes for Metal-Supported Proton-Conducting Electrolysis Cells.
• Norby, Truls; Dayaghi, Amir Masoud; Storhaug, Sjur; Chen, Henry; Haugsrud, Reidar & Stange, Marit Synnøve Sæverud [Show all 9 contributors for this article] (2021). BSZCY151020: A proton ceramic electrolyte with increased TEC for planar applications .
• Stange, Marit Synnøve Sæverud; Stefan, Elena; Denonville, Christelle; Dayaghi, Amir Masoud; Larring, Yngve & Rørvik, Per Martin [Show all 11 contributors for this article] (2021). Processing route for Metal Supported Proton Conducting Ceramic Cells.
• Thoreton, Vincent; Liu, Xin; Li, Zuoan & Haugsrud, Reidar (2021). Effect of water vapour on the oxygen surface exchange kinetics of CaTi0.9Fe0.1O3-δ.
• Thoreton, Vincent; Liu, Xin; Li, Zuoan; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2020). Surface exchange kinetics of CaTi0.9Fe0.1O3-δ.
• Norby, Truls Eivind; Liu, Xin; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2019). Hydride ion conduction.
• Thoréton, Vincent; Bjørheim, Tor Svendsen; Liu, Xin; Li, Zuoan & Haugsrud, Reidar (2019). Influence of water vapour on the surface exchange kinetics of functional oxides.
• Li, Zuoan; Liu, Xin & Haugsrud, Reidar (2019). Dissociation of oxygen on oxides determined by a modified gas phase analysis (GPA).
• Stange, Marit Synnøve Sæverud; Dayaghi, Amir Masoud; Denonville, Christelle; Larring, Yngve; Rørvik, Per Martin & Haugsrud, Reidar [Show all 7 contributors for this article] (2019). Fabrication of Metal-Supported Proton-Conducting Electrolysers with Thin Film Sr- and Ce-Doped BZY Electrolyte.
• Dayaghi, Amir Masoud; Stange, Marit Synnøve Sæverud; Denonville, Christelle; Larring, Yngve; Rørvik, Per Martin & Haugsrud, Reidar [Show all 7 contributors for this article] (2019). Thin-film electrolyte with TEC optimized for metal-supported proton ceramic electrochemical cell.
• Emhjellen, Linn Katinka; Xing, Wen; Li, Zuoan & Haugsrud, Reidar (2019). Electrochemical Transport in Molten/Solid Composite V2O5-ZrV2O7.
• Stange, Marit Synnøve Sæverud; Dayaghi, Amir Masoud; Denonville, Christelle; Larring, Yngve; Rørvik, Per Martin & Haugsrud, Reidar [Show all 7 contributors for this article] (2019). Key challenges in fabrication of metal-supported thin film proton conducting electrolyser cells.
• Norby, Truls Eivind; Kalland, Liv-Elisif Queseth; Løken, Andreas; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2019). Hydration of fluorite-related rare-earth cerates.
• Clark, Daniel Ryan; Malerød-Fjeld, Harald; Budd, Michael; Catalán-Martinez, David; Beeaff, Dustin & Norby, Truls Eivind [Show all 7 contributors for this article] (2018). Design and development of next-generation protonic reactors.
• Stange, Marit Synnøve Sæverud; Denonville, Christelle; Larring, Yngve; Stefan, Elena; Rørvik, Per Martin & Haugsrud, Reidar [Show all 7 contributors for this article] (2017). Manufacturing of Metal Supported Protonic Ceramic Electrolyser Cells (PCEC).
• Haugsrud, Reidar; Chen, Min & Bjørheim, Tor Svendsen (2017). SSPC-18 Conference Special Issue. Solid State Ionics. ISSN 0167-2738. 306. doi: 10.1016/j.ssi.2017.04.012.
• Li, Zuoan & Haugsrud, Reidar (2017). Oxygen dissociation rate of oxide ion conductors determined by a novel gas phase analysis technique .
• Clark, Daniel Ryan; Kjølseth, Christian; Malerød-Fjeld, Harald; Hernandez Morejudo, Selene; Zanon, R. & Serra, J [Show all 11 contributors for this article] (2017). Intensified Conversion of Natural Gas Using Proton-Conducting Ceramics.
• Lervik, Adrian; Bjørheim, Tor Svendsen; Nguyen, Phuong Dan; Diplas, Spyridon; Haugsrud, Reidar & Gunnæs, Anette Eleonora (2016). Chemical and Structural Investigations of Grain Boundaries in Y-Doped BaZrO3.
• Liu, Xin; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2016). Hydride migration and electron localization in BaTiO3-xHx oxyhydride .
• Stange, Marit Synnøve Sæverud; Stefan, Elena; Denonville, Christelle; Fontaine, Marie-Laure; Larring, Yngve & Haugsrud, Reidar (2016). Development of metal supported proton ceramic electrolyser cells (PCEC) for renewable hydrogen production.
• Stange, Marit Synnøve Sæverud; Stefan, Elena; Denonville, Christelle; Larring, Yngve & Haugsrud, Reidar (2016). DEVELOPMENT OF MS-PCEC.
• Stange, Marit Synnøve Sæverud; Stefan, Elena; Denonville, Christelle; Larring, Yngve; Rørvik, Per Martin & Fontaine, Marie-Laure [Show all 7 contributors for this article] (2016). Development of metal supported proton ceramic electrolyser cells (PCEC) for renewable hydrogen production.
• Stange, Marit Synnøve Sæverud; Stefan, Elena; Denonville, Christelle; Larring, Yngve; Rørvik, Per Martin & Haugsrud, Reidar (2016). Progress on development of metal-supported proton conducting electrolysis cells (PCEC).
• Stefan, Elena; Stange, Marit Synnøve Sæverud; Denonville, Christelle; Larring, Yngve; Norby, Truls & Haugsrud, Reidar (2016). Fabrication of Multi-layered Microstructures based on BaZr0.85Y0.15O3-δ for Metal Supported Proton Ceramic Electrolyzer Cells by Pulsed Laser Deposition.
• Løken, Andreas; Haugsrud, Reidar & Bjørheim, Tor Svendsen (2016). Unravelling the Fundamentals of Thermal and Chemical Expansion of Proton Conducting Oxides.
• Løken, Andreas; Olsen, Malin Solheim; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2016). The Effect of Clustering of Acceptors and Oxygen Vacancies on the Hydration and Transport of Proton Conducting Oxides.
• Hasle, Ida Margrete; Vøllestad, Einar; Haugsrud, Reidar; De Souza, Roger; Gries, Ute & Waldow, Stephan (2016). B-site Cation (Zr4+) Diffusion in Yttrium doped Barium Zirconate.
• Hasle, Ida Margrete; Haugsrud, Reidar & Polfus, Jonathan M. (2016). Computational Studies of Cation Transport in Barium Zirconate.
• Løken, Andreas; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2016). The detrimental role of acceptor and oxygen vacancy clustering on the hydration and transport properties of proton conducting oxides.
• Lervik, Adrian; Haugsrud, Reidar; Diplas, Spyridon & Gunnæs, Anette Eleonora (2015). A TEM approach to BZY.
• Løken, Andreas; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2015). Origins of limiting proton concentrations in acceptor doped oxides.
• Løken, Andreas; Bjørheim, Tor Svendsen & Haugsrud, Reidar (2015). Defect Associations as a Potential Cause for Limiting Proton Concentrations in Acceptor Doped Oxides.
• Fjellvåg, Øystein Slagtern; Fjellvåg, Helmer; Liu, Xin; Haugsrud, Reidar & Sjåstad, Anja Olafsen (2015). Hydride oxides with perovskite related structure: Case study of La2LiHO3.
• Hasle, Ida Margrete & Haugsrud, Reidar (2015). Metal Cation Inter-diffusion in BaZr0.9Y0.1O3-δ(BZY).
• Hasle, Ida Margrete & Haugsrud, Reidar (2015). Metal Cation Inter-diffusion in BaZr0.9Y0.1O3-δ(BZY) .
• Norby, Truls; Haugsrud, Reidar & Polfus, Jonathan M. (2015). Defects and transport in proton conducting BZY.
• Stange, Marit Synnøve Sæverud; Denonville, Christelle; Stefan, Elena; Haugsrud, Reidar; Rørvik, Per Martin & Larring, Yngve (2015). Development of thin film based metal supported PCEC.
• Desissa, Temesgen D.; Haugsrud, Reidar & Norby, Truls (2015). Interface properties of p-n junction of oxide thermoelectric materials. Show summary

  Thermoelectric materials are used to convert waste heat to consumable power. Among these materials, oxide thermoelectric materials are emerging as promising candidate materials as they are stable at high temperature and non-toxic as well as environment friendly. In the present work, we are investigating the stability and thermodynamic co-existence at the interface of a newly proposed thermoelectric generator. In this type of module configuration, the p and n legs will be put in direct contact without metallic interconnect. The barrier layer that could be formed at high temperature side could be surmounted by operating at high temperature to increase the generation rate of minority charge carriers. At low temperature side, there will be a recombination of majority charge carriers. This implies that the Ohmic behavior of the materials at p-n junction increases with increasing temperature. Powders such as “Ca3Co4O9” (CCO) and Sr0.9La0.1TiO3 (SLTO) as p-type and n-type, respectively, were used via standard solid state reaction methods of powder synthesis. Then the samples were subjected to characterization and measurements.

• Stange, Marit Synnøve Sæverud; Stefan, Elena; Denonville, Christelle; Larring, Yngve; Dahl-Hansen, Runar & Rørvik, Per Martin [Show all 7 contributors for this article] (2015). Development of metal supported protonic electrolyzer cells (MSD-PCEC).
• Stefan, Elena; Stange, Marit Synnøve Sæverud; Denonville, Christelle; Larring, Yngve; Dahl-Hansen, Runar & Rørvik, Per Martin [Show all 8 contributors for this article] (2015). Characterization of BaZr0.85Y0.15O3-δ Thin Films for Proton Ceramic Electrolyzer Cells by Pulsed Laser Deposition .
• Stefan, Elena; Stange, Marit Synnøve Sæverud; Denonville, Christelle; Larring, Yngve; Dahl-Hansen, Runar & Rørvik, Per Martin [Show all 8 contributors for this article] (2015). Electrode and Electrolyte Microstructures based on BaZr0.85Y0.15O3-δ for Proton Ceramic Electrolyzer Cells by Pulsed Laser Deposition .
• Stefan, Elena; Stange, Marit Synnøve Sæverud; Denonville, Christelle; Dahl-Hansen, Runar; Larring, Yngve & Rørvik, Per Martin [Show all 9 contributors for this article] (2015). Fabrication and Characterization of Metal Supported Proton Ceramic Electrolyzer Cells (PCEC).
• Abbas, Haider; Haugsrud, Reidar & Strandbakke, Ragnar (2022). Defect and transport in Ba7M’4-x MoxO20+z (M’=Nb,Ta). Universitetet i Oslo.
• Storhaug, Sjur; Haugsrud, Reidar & Norby, Truls (2022). Sintering and electrical properties of proton conducting BSZCY151020. Universitetet i Oslo.
• Chen, Henry; Norby, Truls; Haugsrud, Reidar & Dayaghi, Amir Masoud (2022). Sintering Behavior and Conductivity of (Ba0.85Sr0.15)(Zr0.7Ce0.1Y0.2)O3-δ Doped with ZnO as Sintering Aid. Universitetet i Oslo.
• Svee, Tord; Norby, Truls; Haugsrud, Reidar; Strandbakke, Ragnar; Thoreton, Vincent & Clar, Daniel (2021). Surface kinetics of BaGd1-xLaxCo2O6-𝛿 for use as an anode material in proton ceramic electrolyser cells. Universitetet i Oslo. Show summary

  The main topic of this thesis is the surface kinetics of BaGdxLa1-xCo2O6-δ (BGLC), a mixed ionic electronic conducting double perovskite, with operation temperatures between 400-700 °C that shows potential for use as an anode in Proton Conducting Ceramic Electrolysers (PCEC). While showing promise the material is still limited by its surface reactions, notably adsorption and dissociation. To test the variation in surface kinetics with the ratio of lanthanides on the A’-site, five compositions with differing lanthanide content was synthesised with a sol-gel synthesis path: BGLC19 (BaGd0.1La0.9Co2O6-δ), BGLC37 (BaGd0.3La0.7Co2O6-δ), BGLC55 (BaGd0.5La0.5Co2O6-δ), BGLC73 (BaGd0.7La0.3Co2O6-δ) and BGLC91 (BaGd0.9La0.1Co2O6-δ). Acceptable phase purity was determined through X-ray diffractometry (XRD), the batches sieved into four different grain size ranges, with diameters of 63-45 μm being used for all later experiments. Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis were applied to examine the morphology and determine the specific surface area of the samples. Pulse isotope exchange (PIE) and gas phase analysis (GPA) were used to examine the surface kinetics of the samples. The PIE data also allows us to extract the adsorption and incorporation energy of gas species from the total activation energy. Comparative measurements in 21% oxygen at 400 °C for BGLC19 with GPA and PIE resulted in surface exchange coefficients for oxygen of 6.8×10-5 mol m-2 s -1 (PIE) and 1.3×10-5 mol m-2 s -1 (GPA), with the difference being attributed to exchange rates in GPA being limited by gas diffusion in the chamber. An experiment was also performed with PIE on BGLC19 in 21% and 2% oxygen, resulting in surface exchange coefficients of 6.8×10-5 mol m-2 s -1 (21%) and 1.2×10-4 mol m-2 s -1 (2%) at 400 °C. The total activation energy E0 for oxygen exchange was lower in 2% oxygen (0.84 eV in 2% vs 1.1 eV in 21%), but with a slightly higher adsorption energy Eads (0.79 eV in 2% vs 0.62 eV in 21%). Measurements were also performed with PIE in 2% oxygen across compositions, with BGLC55 showing the lowest incorporation energy Einc for oxygen at 0.82 eV but with the highest E0 (0.91 eV) and Eads (0.92 eV) of the set. BGLC73 displayed the lowest values for total activation and adsorption energies at 0.62 eV (E0) and 0.69 eV (Eads). The highest surface exchange rates for oxygen were measured for BGLC19, BGLC73 and BGLC91 at over 1×10-4 mol m-2 s -1 , while the values for BGLC37 and BGLC55 were around 6×10-4 mol m-2 s -1 . 3 PIE experiments involving the exchange of water vapour were also performed on BGLC37 and BGLC91, with BGLC73 exchanging the most water up to 450 °C. With unclear data and very little to no D2O measured by the mass spectrometer, these experiments remain inconclusive.

• Alsgaard, Erik Erlend Pham; Norby, Truls; Haugsrud, Reidar & Bjørheim, Tor Svendsen (2021). Protonic Transport Properties of Perovskite Heterostructures. Universitetet i Oslo. Show summary

  Proton ceramic fuel cells based on an yttrium-doped barium zirconate electrolyte might pose as a viable option for future hydrogen applications. High resistances in the electrolyte however hampers the performance of the material. Therefore, a novel heterostructure engineering strategy is applied in order to investigate alternative solutions to reducing the resistances. This thesis aims to deepen our understanding of how heterostructures and their interfaces might affect the electrolyte resistances. The goal of the following approach is to circumvent proton trapping at acceptor dopant sites. A job-sharing model has been investigated where one phase “supplies” the protons while the other phase conducts them. The proton donor phase is acceptor doped and more acidic than the other phase, resulting in a net transfer of protons over to the conductive phase. The latter phase, free of trap sites and enriched in charge carriers, is then hypothesized to exhibit a conductivity increase. Modern computational methods allow for compositions to be investigated theoretically without having to perform tedious experiments. While experiments measure the actual effects of the system of interest, the results might be ambiguous as they often are a combination of several contributions. Theoretical computations on the other hand might give insight into trends, often on the atomistic scale, else impossible to separate from other effects experimentally. Combining the two methods, in depth knowledge and understanding of the system is acquirable. The model system, an alternating multi layered BaZr1-xYxO3/SrTi1-xScxO3 film was fabricated by pulsed laser deposition onto a (100) MgO substrate. The thin (60 nm) films were by X-ray diffraction confirmed to be grown epitaxially, made possible by a good lattice match between the substrate and the films. Impedance spectroscopy measurements of the BaZrO3/SrTi0.9Sc0.1O3 film showed a conductivity of 0.27 mS/cm, comparable to the conductivity of the reference BaZr0.9Y0.1O3 film (0.28 mS/cm). The activation energy of the heterostructure was measured to 0.45 eV, lower than for the reference BaZrO3 and BaZr0.9Y0.1O3 films and in the range of the proton migration activation energy. The SrTi0.9Sc0.1O3 had a larger activation energy of 0.64 eV, expected for oxide ion conduction mechanism. VII When going to dry from humid atmosphere for the BaZr1-xYxO3 containing films was a decrease in conductivity of 55 % to 65 %, attributed to a decrease in charge carrier (proton) concentrations which was further confirmed by a hydrogen isotope exchange. A slope of 0.143 was observed in the Arrhenius plot of the SrTi0.9Sc0.1O3 film, indicating that ionic defects dominate concentration-wise whilst minority holes contribute significantly to the conductivity in the measured pO2 range. First principles calculations of a BaZr0.984Y0.016O3H0.016 4 by 4 supercell showed the energy difference a at set of Y-H + distances. The trapping energy of the protons was calculated as a function of in-plane strain and was found to increase with more negative (compressive) strain. Additionally, strain in general decreases the long-range mobility of protons in the yttrium dopants because of an energy barrier, larger than or equal to the trapping energy. Removing -0.5 % of strain was found to result in an activation energy decrease, increasing the conductivity by a factor of two. The calculated trapping energy change for different levels of strain agree well with experimental activation energies from literature [1]. Comparisons of measurements between reference films and the BaZrO3/SrTi0.9Sc0.1O3 heterostructure supports the job-sharing model. By assuming that the space charge region of the BaZrO3 and SrTi0.9Sc0.1O3 does not affect the conductivity of the latter, a conductivity increase of a factor of 14 was calculated for the BaZrO3 layer of the heterostructure compared to the reference BaZrO3 film.

• Mäntysalo, Visa Aleksi & Haugsrud, Reidar (2021). Synthesis and Characterization of La4BaCu5-xCoxOα as a Positrode for Proton Ceramic Electrochemical Cells - An Experimental and First Principles Investigation. Universitetet i Oslo.
• Kalland, Liv-Elisif Queseth; Norby, Truls Eivind; Mohn, Chris Erik & Haugsrud, Reidar (2021). Ab-initio modelling and experimental study of order-disorder, hydration, and ionic conductivity of fluorite-related oxides. Matematisk Naturvitenskapelig fakultet, Universitetet i Oslo. ISSN 1501-7710. 2021(2348). Show summary

  Hydrogen will play a key role in a zero-emission society, and proton (H+) conducting oxides have gained interest as solid-state electrolytes for next-generation electrochemical devices for fuel cells and electrolyzers. Understanding the effect of structure on materials functional properties is important for enhancing the performance of such electrolytes. Oxides with fluorite related crystal structures are interesting for their high oxide ion and proton (H+) conductivities, and in this work the relationship between the atomic structure and the materials properties such as ionic conductivity and hydration properties have been studied for three different oxides. They are oxygen deficient with respect to the fluorite structure and the vacant oxide ion sites can thus be ordered or disordered. Through a combination of different experimental and computational methods the nature and degree of ordering and the atomic structure have been determined, and correlated to the properties of the cations present, such as size and electronegativity. The work further focuses on whether ordering the oxide ion vacancies affects the hydration and consequently the proton conductivity. The results have led us to propose a new model for hydration of heavily doped yet disordered fluorite oxides.

• Westvold Johansen, Hege; Haugsrud, Reidar & Strandbakke, Ragnar (2020). Defects and transport in donor doped LaNbO4. Universitetet i Oslo.
• Johansen, Hege Westvold & Haugsrud, Reidar (2020). Defects and transport in donor doped LaNbO4. Universitetet i Oslo.
• Liu, Xin; Haugsrud, Reidar; Bjørheim, Tor Svendsen & Fjellvåg, Helmer (2018). Defect, Stability and Transport in Oxyhydrides. Universitetet i Oslo. ISSN 1501-7710.
• Desissa, Temesgen D.; Norby, Truls Eivind & Haugsrud, Reidar (2018). Stability and properties of materials and interfaces for oxide thermoelectrics. Universistetet i Oslo. ISSN 1501-7710. 2018(1969).
• Emhjellen, Linn Katinka; Haugsrud, Reidar; Bjørheim, Tor Svendsen & Strandbakke, Ragnar (2017). Defects and Transport in SrFe1-xMoxO3-δ. Universitetet i Oslo.
• Løken, Andreas; Haugsrud, Reidar; Norby, Truls Eivind & Bjørheim, Tor Svendsen (2017). Hydration thermodynamics of oxides. Universitetet i Oslo.
• Stub, Sindre Østby; Haugsrud, Reidar & Norby, Truls Eivind (2017). Protonic Conduction in Porous Oxides. Universitetet i Oslo.
• Gutterød, Emil Sebastian; Haugsrud, Reidar & Polfus, Jonathan M. (2016). An Experimental and Computational Study of Nitrogen Activation on Promoted Ruthenium Catalysts. Universitetet i Oslo. Show summary

  Ruthenium based catalysts for ammonia synthesis have been studied extensively following the industrial adoption of a promoted carbon supported ruthenium catalyst in the Kellogg Advanced Ammonia Process (KAAP). Nevertheless, there are still fundamental aspects such as the dissociative adsorption of nitrogen—generally regarded as the rate determining step of NH3 synthesis—and the influence of the barium promoter, not fully explored. In the present work, the activation of nitrogen on barium promoted ruthenium is elucidated through a combined experimental and computational approach. Nitrogen dissociation and association on a clean and barium promoted Ru(0001) step were investigated through DFT based calculations using VASP. Unpromoted dissociation was found to proceed with an energy barrier of 51 kJmol−1, with a N-N distance of the transition state (TS) of 1.864 Å. The calculated activation barrier for association was 135 kJmol−1, which increased to 161 kJmol−1 when diffusion of atomic nitrogen along the terrace was considered. Upon promotion by a unit of atomic Ba, BaOH and BaO at the step, the dissociation barrier decreased rather similarly by 21, 18 and 18 kJmol−1, respectively. The chemical state of the promoting unit was determined to have a larger effect on the association barrier, which decreases by 19, 10 and 5 kJmol−1, respectively. A previously not reported local energy minimum state with one nitrogen atom adsorbed on the b5-hcp site and the other at a step-bridge site was identified. A significant stabilization of the local minimum state is observed upon promotion: the N-N distance of the initial and final state of dissociation increased (which can be associated with a weakening of the N-N bond), while it decreased for the TS and the local minimum state. The promoting effect decreases rapidly with increasing distance to the dissociating nitrogen, indicating that the interactions were of electronic nature. Powdered catalyst samples of Ru-Ba/AC were prepared by Ba(NO3)2 wet-impregnation of 5 wt% Ru on activated carbon. The nitrogen isotope exchange (IE) reaction 14,14N2 + 15,15N2 = 214,15N2 on Ru-Ba/AC was investigated in the temperature range 320– 750°C at N2 pressures of 20–230mbar, by means of gas-phase analysis with mass spectrometry (GPA-MS). Apparent isotope exchange activation energies in range 162– 178 kJmol−1 were obtained below 425°C. This is in good agreement with the literature and the present computational results. At higher temperatures the apparent activaiii Abstract tion energy abruptly decreases to 64–88 kJmol−1. It is suggested that the change in temperature dependence is due to limitations by pore diffusion at higher temperatures. In the presence of 1mbar water vapor in the temperature range 575–625°C, the isotope exchange rate was significantly reduced compared to under dry conditions, and the apparent activation energy increased from 88 ± 2 kJmol−1 to 126 ± 12 kJmol−1. When water vapor was introduced, evolution of H2 was observed, indicating that oxidation of partially reduced Ba occurred in the presence of H2O. Isotherms of the isotope exchange rate showed reaction orders with respect to nitrogen partial pressure of 0.83 ± 0.05 and 0.88 ± 0.03 at 625°C and 700°C, respectively, and 1.1 at 450°C. All of which are in good agreement with values reported in literature for NH3 synthesis. Deactivation of the catalyst was observed at temperatures above 500°C, resulting in a significantly decreasing IE rate with time. In accordance with reports from literature, and the computational and experimental results, it is proposed the isotope exchange rate and activation energy are highly dependent on the chemical state of the barium promoter, which is further dependent on the environmental conditions, such as temperature and the presence of water vapor. iv

• Prato Modestino, Rafael Albert; Haugsrud, Reidar; Strandbakke, Ragnar & Vøllestad, Einar (2016). TRANSPORT PROPERTIES AND SURFACE KINETICS OF Ba0.8+xGd0.8La0.2+xCo2O6-d. Universitetet i Oslo. Show summary

  The main topics of this thesis are the surface kinetics and bulk diffusion of oxygen in Ba(1-x)Gd0.8La(0.2+x)Co2O(6-d) (BGLC). Previous work has identified BGLC as very promising electrode material for SOFC’s and electrolyzers. With conductivities in the range of ~1000 S/cm and polarization resistances in the order of 10^-2 Ocm2 around operating temperatures (i.e. 500-700 ºC). BGLC is in line to surpass current state of the art materials. Yet in order to introduce a new electrode, thorough characterization needs to be performed on its physicochemical properties. BGLC has been identified as double perovkite (double on the c-axis) by x-ray diffractometry (XRD), and synchotron measurements, in the form of AA'B2O(6-d). Cobalt occupies the B sites at the cell’s corners, with octahedral coordination of oxygen atoms, while barium and the lanthanides occupy the center of each square cell. Such a structure is highly defective; the heterovalency between barium and the lanthanides introduces oxygen vacancies in the material. The perfect structure is defined at BaGd0.8La0.2Co2O6 in order to establish a defect model. It is suggested that cobalt ions of differing valence (+2, +3 and +4) are evenly distributed through the material, and that the oxygen sites are ordered in layers surrounding the different cations. From this starting point, effects of temperature and atmosphere on the structure and properties of BGLC is studied. High temperature in-situ XRD in the temperature range from 25 to 800 ºC shows little change in the structure. As opposed to other perovskites (ex.: GdBaCo2O6-d), BGLC remains stable through operating temperatures. Lanthanum can be used to dope the barium sites without compromising stability, leading to more compositions. Synchotron data shows the majority of oxygen vacancies aggregated in the lanthanide layer (O1 site), a reduced amount in the cobalt layer (O2 site), and no vacancies present in the barium layer (O3 site). Such a flexible structure can be reduced or oxidized easily. Changes in temperature using a thermal balance revealed the oxygen non-stoichiometry as function of temperature down to [O] ~4.9. The same experiments were performed isothermally with changing pO2. The defect model proposed is able to model the data closely for BGLC and related double perovskites. These oxygen vacancies allow for ionic diffusion through the material. The transport regimes were divided in two: surface exchange of oxigen, and bulk diffusion (self-, chemical, and tracer). Thermogravimetry (TG), isotope exchange gas phase analysis (GPA) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) were employed to measure the diffusion coefficients (D) and surface coefficient (k) of BGLC at various temperatures between 350 to 800 ºC. Dchem was measured to 10^-6 to 10^-7 cm2/s at relatively low temperatures of 600 – 500 ºC with an equally low activation energy of ~0.74 eV. This leads to an oxide ion conductivity of 10^-2 to 10^-3 S/cm at operating conditions. The values were found to be competitive with state-of-the-art materials in literature. The pre-exponential values and activation energies are in close agreement to related double perovskites such as GdBaCo2O6-d and PrBaCo2O6-d. The oxygen surface exchange was studied using GPA, where a mass spectrometer tracks the concentration of species in the gas phase of a reaction chamber. Various reaction sequences are proposed for the oxygen exchange process of adsorption-dissociation-association-desorption. The desorption/adsorption steps were found to be rate limiting for this material. The surface exchange coefficient, k, is characterized by 6.0*10^-2 Exp(-66570/RT), a high value for k0 and low Ea for perovskites, but on par with novel double-perovskites. An imporant of feature of BGLC is the relatively high proton content (~1 mol%) under wet atmosphere. The hydration properties are included and modeled in the defect structure.

• Lervik, Adrian; Haugsrud, Reidar; Diplas, Spyridon & Gunnæs, Anette Eleonora (2016). Structural- and Compositional Investigations of Grain Boundaries in Y-Doped BaZrO3. Universitetet i Oslo.
• Morland, Bjørn Helge; Dugstad, Arne & Haugsrud, Reidar (2015). Corrosion in CO2 transport pipeline The effect of dissolved and free water in dense phase CO2. Universitetet i Oslo. Show summary

  The carbon dioxide (CO2) concentration in the atmosphere has increased dramatically over the last century, and much of this increase is a direct consequence of human activities. Being a greenhouse gas, CO2 significantly contributes to global warming, and there is an international agreement to reduce emission of CO2. One method to reduce CO2 release is carbon dioxide capture and storage (CCS). CCS entails to capture waste CO2 from large point sources, and transport it to a permanently deposit, usually in geological formations. The transported CO2 is likely to contain impurities like water, oxygen, nitrogen dioxide, sulfur dioxide and hydrogen sulfide. These impurities are known to cause corrosion, dust and/or solid formations, and may lead to operational difficulties. The present study examined how water as an impurity, both as a free water phase and water dissolved in dense phase CO2, affects the corrosion of carbon steel. There are few experimental studies that have examined corrosion in CO2 transport pipelines, and these few studies have shown different corrosion rates in experiments where the reported amount of dissolved water in the CO2 was the same. These discrepancies may reflect short-comings in methodology in some of these studies, where formation of free water may have contributed to high corrosion rates. The present study was undertaken to resolve some of the controversy related to corrosion in pure CO2/water systems. For this study we designed experimental equipment that allowed complete control of the water concentration in CO2, without the risk of droplet formation. This provides realistic results that mimic the situation in the operating pipelines. Three corrosion experiments were conducted with water dissolved in CO2 at 25 °C and 95 bar of pressure. Even with water concentrations close to the solubility limit, the general corrosion rates were below 1.5 µm/y and no localized attacks were found. A fourth experiment was conducted at and above the solubility limit of water in CO2. Even though we could confirm at the end of the experiment that water had accumulated in the loop, the corrosion rate was still at 1.0 µm/y, with no localized attacks. A final experiment was performed at 35 °C and 95 bar of pressure, in which no corrosion was detected. Corrosion products were found on the surface in all experiments, but at low quantities, most likely less than of practical significance. However, with water levels above the solubility limits, i.e. in the present of free water phase, the corrosion rate increased by 3 to 4 orders of magnitude (2 mm/y to 16 mm/y, pressure depended). For a CO2 transport pipeline these results suggest that the corrosion will not be a problem as long as the water is kept below the solubility limit. However, it is extremely important to avoid liquid water ingress as this would dramatically reduce the lifetime of the pipeline.

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