Yilmaz, Meltem; (2023) Applications of Copper Oxide Based Photo- And Electro-Catalysts for Energy and Environmental Catalysis. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The research described in this thesis is focussed on copper and its oxide derivatives for their use in energy and environmental catalysis. More specifically, photoelectrochemical water splitting for hydrogen evolution and electrocatalytic CO2 reduction reactions have been explored. Initially, structural, and functional variations in a series of systematically electrodeposited photoactive Cu2O films were explored. This was done by implementing a quantitative analysis of high energy resolution fluorescence X-ray absorption spectroscopy (HERFD-XANES). Bulk versus surface structure was further explored using a range of techniques like X-ray diffraction, UV-Vis, Raman and X-ray photoelectron spectroscopies. This work revealed a descriptor between the Cu2+/Cu+ ratio and the photoelectrocatalytic performance, highlighting the importance of XAS based techniques for use on thin film catalysts relating to energy conversion and generation applications. Architectural modification of multi-layered Cu2O films was then explored. Atomic layer deposition (ALD) of TiO2 and ZnO were investigated as protection layers to impede the reductive decomposition of Cu2O to Cu. Further modification was carried out by depositing MXenes, Mo2CTx and Ti3C2Tx, as HER cocatalysts. To the authors best knowledge, this is the first time in which these two-dimensional metal carbides have been interfaced with Cu2O photocathodes to be used in a photoelectrochemical system. This approach yields a photocathode which is 4.38-fold more active that bare Cu2O at 0 V vs RHE. Design and development of active and selective electrocatalysts for CO2 reduction is a topic of ongoing research. In the last part of this thesis, histidine functionalised Cu2O nanoparticles were explored for their electrocatalytic CO2 reduction properties. A highlight of this study was the high C2 selectivity discovered on these catalysts. Beyond selectivity, an unexpected wide operation potential window leaning into more negative potentials for certain catalysts was discovered. This demonstrates their potential use in industrially more viable gas diffusion electrodes.

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