Functional Grading by Key doping in Catalytic electrodes for Proton Ceramic Cells (FunKeyCat) (avsluttet)

• Carrillo, Alfonso; Balaguer, M.; Solis, Cecilia; Lopez-Garcia, Andres; Haas, Sylvio & Fabuel, Maria [Vis alle 13 forfattere av denne artikkelen] (2025). Evaluating oxide nanoparticle exsolution on A-site deficient PrBaCo2O6-δ electrodes. Journal of Physics: Energy. 7(2), s. 1–15. doi: 10.1088/2515-7655/ada8de. Fulltekst i vitenarkiv Vis sammendrag

  Nanoparticle exsolution is a powerful technique for functionalizing redox oxides in energy applications, particularly at high temperatures. It shows promise for solid oxide fuel cells and electrolyzers. However, exsolution of other chemistries like metal oxides is not well studied, and the mechanism is poorly understood. This work explores oxide exsolution in PrBa1−xCo2O6−δ (x = 0, 0.05, 0.1, 0.15) double perovskites, practiced electrodes in proton ceramic fuel cells and electrolyzers. Oxide exsolution in PrBa1−xCo2O6−δ aimed at boosting the electrocatalytic activity and was evaluated by varying intrinsic materials-related properties, viz. A-site deficiency and external parameters (temperature, under fixed time, and pO2 = 10−5 atm conditions). The materials were analyzed with conventional characterization tools and synchrotron-based small-angle x-ray scattering. Unlike metal-nanoparticle exsolution, increasing the A-site deficiency did not enhance the extent of oxide-nanoparticle exsolution, whereas larger nanoparticles were obtained by increasing the exsolution temperature. Combined Raman spectroscopy and electron microscopy analysis revealed that BaCoO3, Co3O4, and amorphous BaCO3 nanoparticles were formed on the surface of the double perovskites after the reductive treatments. The present results demonstrate the complexity of oxide-nanoparticle exsolution in comparison with metal-nanoparticle exsolution. Further materials screening and mechanistic studies are needed to enhance our understanding of this method for functionalizing proton ceramic electrochemical cells (PCEC) electrodes.

• Balcerzak, Daria; López-García, Andrés; Carrillo, Alfonso J.; Balaguer, María; Alfaro, Jose Manuel Serra & Norby, Truls [Vis alle 9 forfattere av denne artikkelen] (2025). Tailoring oxide nanoparticle exsolution in La0.5Ba0.5-yCo1-xFexO3-δ. Journal of the European Ceramic Society. ISSN 0955-2219. 45(10), s. 1–12. doi: 10.1016/j.jeurceramsoc.2025.117347. Fulltekst i vitenarkiv Vis sammendrag

  We show that oxide nanoparticles (NPs) exsolve on La0.5Ba0.5-yCo1-xFexO3-δ (x = 0–1, y = 0 or 0.01) in oxidizing conditions. The phenomenon occurs only in Co-containing materials and depends on pO2 and pH2O pressures. Under dry conditions, the smallest NPs average about 30 nm, with 200–300 NPs/µm2 at pO2= 5 × 10−5 atm. For pO2= 1 atm, NP size increases to 100–200 nm, and population drops to a few to about 20 NPs/µm2 depending on A-site nonstoichiometry and x. In humid conditions, the smallest NPs around 50 nm, with a peak of 100 NPs/µm2 exsolve for pO2= 1. Transmission electron microscopy shows that exsolved NPs in La0.5Ba0.5-yCoO3-δ are Ba-O-rich. We propose defect chemistry models, indicating that exsolution is driven by oxidation reactions forming A-site vacancies, increasing exsolved material with higher pO2. We suggest that adsorbed water under humid conditions blocks nucleation sites, altering observed trends.

• Pośpiech, Joanna; Nadolska, Małgorzata; Cieślik, Mateusz; Sobczyk, Tomasz; Chmielewski, Marek & Mielewczyk-Gryń, Aleksandra [Vis alle 9 forfattere av denne artikkelen] (2024). Additive manufacturing of Proton-Conducting Ceramics by robocasting with integrated laser postprocessing. Applied Materials Today. ISSN 2352-9407. 40. doi: 10.1016/j.apmt.2024.102398. Fulltekst i vitenarkiv Vis sammendrag

  A hybrid system combining robocasting and NIR laser postprocessing has been designed to fabricate layers of mixed proton-electron conducting Ba0.5La0.5Co1-xFexO3-δ ceramic. The proposed manufacturing technique allows for the control of the geometry and microstructure and shortens the fabrication time to a range of a few minutes. Using 5 W laser power and a scanning speed of 500 mm·s−1, sintering of a round-shaped layer with an 8 mm radius was performed in less than 2 s. The single phase of the final product was confirmed by X-ray diffraction. Various ceramic-to-polymer weight ratios were tested, showing that various porosities of microstructures of ∼30 - 35 % and ∼19 % can be obtained with 2:1 and 4:1 loading respectively.

• Balcerzak, Daria; Szpunar, Iga; Strandbakke, Ragnar; Saeed, Sarmad W.; Bazioti, Calliope & Mielewczyk-Gryń, Aleksandra [Vis alle 12 forfattere av denne artikkelen] (2023). Oxide nanoparticle exsolution in Lu-doped (Ba,La)CoO₃. CrysteEngComm. 25(30), s. 4316–4316. doi: 10.1039/d3ce00422h. Fulltekst i vitenarkiv Vis sammendrag

  This study investigated Lu doping of Ba 0.5 La 0.5 CoO 3 and its influence on the exsolution of oxide nanoparticles (NPs).

• Balcerzak, Daria; Szpunar, Iga; Strandbakke, Ragnar; Saeed, Sarmad Waheed; Bazioti, Kalliopi & Mielewczyk-Gryń, Aleksandra [Vis alle 12 forfattere av denne artikkelen] (2023). Oxide nanoparticle exsolution in Lu-doped (Ba,La)CoO3. CrysteEngComm. 25(30), s. 4306–4316. doi: 10.1039/d3ce00422h. Fulltekst i vitenarkiv
• Zhu, Junjie; Gudmundsdottir, Jonina Björg; Strandbakke, Ragnar; Both, Kevin Gregor; Aarholt, Thomas & Carvalho, Patricia Almeida [Vis alle 12 forfattere av denne artikkelen] (2021). Double Perovskite Cobaltites Integrated in a Monolithic and Noble Metal-Free Photoelectrochemical Device for Efficient Water Splitting. ACS Applied Materials & Interfaces. ISSN 1944-8244. 13(17), s. 20313–20325. doi: 10.1021/acsami.1c01900. Fulltekst i vitenarkiv Vis sammendrag

  Water photoelectrolysis has the potential to produce renewable hydrogen fuel, therefore addressing the intermittent nature of sunlight. Herein, a monolithic, photovoltaic (PV)-assisted water electrolysis device of minimal engineering and of low (in the μg range) noble-metal-free catalysts loading is presented for unassisted water splitting in alkaline media. An efficient double perovskite cobaltite catalyst, originally developed for high-temperature proton-conducting ceramic electrolyzers, possesses high activity for the oxygen evolution reaction in alkaline media at room temperatures too. Ba1–xGd1–yLax+yCo2O6−δ (BGLC) is combined with a NiMo cathode, and a solar-to-hydrogen efficiency of 6.6% in 1.0 M NaOH, under 1 sun simulated illumination for 71 h, is demonstrated. This work highlights how readily available earth-abundant materials and established PV methods can achieve high performance and stable and monolithic photoelectrolysis devices with potential for full-scale applications.

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• Strandbakke, Ragnar (2023). Hydration, stability and electrochemistry of electrode materials for proton ceramic electrochemical cells. Fulltekst i vitenarkiv
• Vøllestad, Einar (2022). A discussion on the electrochemistry of PCEC electrodes. Fulltekst i vitenarkiv
• Balaguer, Maria; Wachowski, Sebastian Lech; Szpunar, Iga; Mielewczyk-Gryn, Aleksandra; Sørby, Magnus Helgerud & Carvalho, Patricia A. [Vis alle 10 forfattere av denne artikkelen] (2022). Double perovskite mixed conductors – Hydration, red-ox, structure and stability. Fulltekst i vitenarkiv
• Norby, Truls Eivind (2021). Electrode kinetics in fuel cells and electrolysers. Fulltekst i vitenarkiv Vis sammendrag

  Fuel cells constitute the technology of choice to convert hydrogen to electricity, while electrolyzers will be a major technology for producing that hydrogen from electricity from renewable sources, notably indirect (hydroelectric, wind, wave) and direct (photovoltaic) solar energy. They are hence not directly the topic of a workshop on solar fuels, but photoelectrochemical (PEC) electrode kinetics is such a complex matter that it is useful to have electrode kinetics of fuel cells and electrolyzers as kind of reference. Both PEC and fuel cells and electrolyzers have in common that established state-of-the-art versions have aqueous liquid electrolytes, while solid-state electrolytes are of increasing interest. We will cover both, and dwell on various intermediate cases. While various charge carrying ions are in use in different ranges of temperature (O2-, CO32-, H+, OH-, H3O+), protonic electrolytes are most central to PEC and we will focus on them, with examples from proton ceramics, proton exchange membranes (PEMs), hydroxide ion conducting polymers, and surface protonic conduction. The electrode reaction comprises faradaic charge transfer over the electrolyte-electrode interface. This can be an electron transfer (redox) or – in the case of mixed ion electron conducting electrodes – ion transfer, in which case the electron transfer must take place somewhere else, e.g. on the electrode surface. The charge transfer – which is our means of driving the reaction with a voltage or recording a current in a chemically driven fuel cell – may be hindered by the supply of reactants, making adsorption and dissociation appear in the polarization resistance. In addition, diffusion in gas phase, over surfaces, and in the bulk of the electrode or electrolyte slows the reaction further and may eventually limit the current. While charge transfer takes place over the double layer capacitance of the electrolyte-electrode interface, the other processes may store reactants and products as much higher chemical capacitance, whereby the different processes have different time constants and may be separated in impedance spectroscopy. The talk will go through materials, processes, and methods, look to general principles that can be applied across systems and technologies, where possible also photoelectrochemical cells for solar hydrogen and artificial photosynthesis.

• Strandbakke, Ragnar; Balaguer, María; Carrillo, Alfonso; Wachowski, Sebastian Lech; Mielewczyk-Gryń, Aleksandra & Szpunar, Iga [Vis alle 13 forfattere av denne artikkelen] (2021). Hydration and electrochemistry of mixed conducting cobaltites. Fulltekst i vitenarkiv
• Strandbakke, Ragnar; Balaguer, María; Carrillo, Alfonso; Wachowski, Sebastian Lech; Mielewczyk-Gryń, Aleksandra & Szpunar, Iga [Vis alle 14 forfattere av denne artikkelen] (2021). Hydration and electrochemistry of mixed conducting cobaltites. Fulltekst i vitenarkiv
• Saeed, Sarmad Waheed & Strandbakke, Ragnar (2020). Resent Activities in FunKeyCat. Fulltekst i vitenarkiv
• Strandbakke, Ragnar; Saeed, Sarmad Waheed & Carrillo, Alfonso (2019). Exsolution activities in the FunKeyCat project: Exsolving oxide nano-catalysts from cathode materials. Fulltekst i vitenarkiv
• Saeed, Sarmad Waheed & Strandbakke, Ragnar (2019). FunKeyCat - An Overview. Fulltekst i vitenarkiv

Se alle arbeider i NVA