Christian Fleischer

• Sun, Xinwei; Xu, Kaiqi; Fleischer, Christian; Liu, Xin; Grandcolas, Mathieu & Strandbakke, Ragnar [Vis alle 9 forfattere av denne artikkelen] (2018). Earth-abundant electrocatalysts in proton exchange membrane electrolyzers. Catalysts. ISSN 2073-4344. 8:657(12), s. 1–41. doi: 10.3390/catal8120657. Fulltekst i vitenarkiv Vis sammendrag

  In order to adopt water electrolyzers as a main hydrogen production system, it is critical to develop inexpensive and earth-abundant catalysts. Currently, both half-reactions in water splitting depend heavily on noble metal catalysts. This review discusses the proton exchange membrane (PEM) water electrolysis (WE) and the progress in replacing the noble-metal catalysts with earth-abundant ones. The efforts within this field for the discovery of efficient and stable earth-abundant catalysts (EACs) have increased exponentially the last few years. The development of EACs for the oxygen evolution reaction (OER) in acidic media is particularly important, as the only stable and efficient catalysts until now are noble-metal oxides, such as IrOx and RuOx. On the hydrogen evolution reaction (HER) side, there is significant progress on EACs under acidic conditions, but there are very few reports of these EACs employed in full PEM WE cells. These two main issues are reviewed, and we conclude with prospects for innovation in EACs for the OER in acidic environments, as well as with a critical assessment of the few full PEM WE cells assembled with EACs.

• Fleischer, Christian; Chatzitakis, Athanasios Eleftherios & Norby, Truls Eivind (2018). Intrinsic photoelectrocatalytic activity in oriented, photonic TiO2 nanotubes. Materials Science in Semiconductor Processing. ISSN 1369-8001. 88, s. 186–191. doi: 10.1016/j.mssp.2018.08.009. Vis sammendrag

  In this work, we grow oriented photonic TiO2 nanotubes (TNTs) with a well-established anodization method and their intrinsic catalytic and electronic properties are studied by means of (photo)electrochemical methods. The oriented photonic TNTs are assessed by the RctCdl (ΩF) product, which is a measure of the intrinsic photoelectrocatalytic activity (IPA) of the material. The RctCdl product decouples any surface area effects and it can be applied at any potential and accompanied reaction without knowing the actual electrochemically active surface area (EASA). Moreover, electrochemical impedance spectroscopy (EIS) is used in order to investigate the frequency dispersion in the single frequency Mott-Schottky (MS) measurement. The choice of frequency and the frequency dispersion in MS measurements in nanostructured and of high surface area semiconductors are rarely addressed and can result in erroneous values of two important parameters, i.e. flat band position and donor or acceptor densities. This work provides further insights into important electrochemical aspects and catalytic properties of high surface area nanomaterials for photoelectrochemical applications.

• Gorbitz, Carl Henrik; Wragg, David; Bakke, Ingrid Marie Bergh; Fleicher, Christian; Grønnevik, Gaute & Mykland, Maria [Vis alle 10 forfattere av denne artikkelen] (2016). A phase transition from monoclinic C2 with Z' = 1 to triclinic P1 with Z' = 4 for the quasiracemate L-2-aminobutyric acid–D-methionine (1/1). Acta Crystallographica Section C: Crystal Structure Communications. ISSN 0108-2701. 72, s. 536–543. doi: 10.1107/S2053229616008858.

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• Fleischer, Christian; Bjørheim, Tor Svendsen; Polfus, Jonathan M. & Norby, Truls Eivind (2018). Point Defects in Monolayer MoS2.
• Fleischer, Christian; Bjørheim, Tor Svendsen & Norby, Truls Eivind (2018). Point Defects in Transition Metal Dichalcogenides. Vis sammendrag

  Defect chemistry has given the possibility to control and tune properties to obtain better functional bulk materials. In comparison, and despite the recent interest and prospects of twodimensional materials, their defect chemistry remains mainly unexplored. We believe that an understanding of the influence of the dielectric environment on the defect chemistry and properties is crucial for further developing new and superior 2D materials. Here, we present results from our computational work on selected point defects in monolayer MoS2. Investigated defects comprises molybdenum and sulphur vacancies in addition to hydrosulfide on sulphur site.

• Fleischer, Christian; Polfus, Jonathan M.; Bjørheim, Tor Svendsen & Norby, Truls Eivind (2018). Defect Chemistry of Few- and Monolayer MoS2. Vis sammendrag

  Defect chemistry has given the possibility to control and tune properties to obtain better functional bulk materials. In comparison, and despite the recent interest and prospects of two-dimensional materials, their defect chemistry remains mainly unexplored. We believe that an understanding of the influence of the dielectric environment on the defect chemistry and properties is crucial for further developing new and superior 2D materials. Here, we present results for molybdenum disulphide (MoS2) films on Si/SiO2 substrates. Methods comprise magnetron sputtering of Mo with subsequent annealing in H2S atmosphere and the chemical vapour transport method. The films and defects are characterised by AFM, XPS, photoluminescence, optical microscopy and Raman spectroscopy in addition to electrical measurements in controlled atmospheres. Ab initio computations on a variety of point defects and defect clusters further elucidate the defect chemistry.

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