Development of scalable metal oxide-based materials for photoelectrochemical water splitting George Creasey 1 , McCallum, Tristan 2 ; Rodriguez Acosta, John 1 ; Kafizas, Andreas 2,3 ; Hankin, Anna 1,4 1 Department of Chemical Engineering, Imperial College London, UK, 2 Department of Chemistry, Imperial College London, UK, 3 London Centre for Nanotechnology, Imperial College London, UK, 4 Institute for Molecular Science and Engineering, Imperial College London, UK While hydrogen production via photoelectrochemical water splitting has been demonstrated on a small scale, developing an industrial scale device is a challenge that intrigues and brings together researchers from a range of disciplines. A key bottleneck in the scalability of PEC devices remains the development of scalable photocatalyst materials for the water splitting reaction. Many photoelectrodes are produced as thin films on transparent conducting oxides, such as fluorine-doped tin oxide (FTO) or indium-doped tin oxide (ITO). However, one difficulty to overcome is the resistivity of FTO glass, which can result in severe resistance losses in scale-up. I will present initial steps we have taken to mitigate this issue. I will present our method of photoanode fabrication, by chemical vapour deposition, a prevalent and scalable method, of sequential layers of WO 3 nanorods and BiVO 4 , to form a staggered heterojunction on FTO. The 2.4 to 2.5 eV bandgap of BiVO 4 enables light absorption up to 517 nm in wavelength and a theoretical solar-to-hydrogen efficiency (ษณ STH ) of up to 9.2 %. The WO 3 /BiVO 4 heterojunction system is one of the most promising in terms of performance, cost and durability. Combined with a Ni mesh cathode and homojunction Si PV, and operated in a pH neutral phosphate buffer solution, this creates a cost-effective and scalable tandem photoelectrochemical- photovoltaic (PV-PEC) device with a commercially viable fabrication method. However, one of the main challenges to address is the PEC stability of BiVO 4 -based photoanodes, which are prone to photocorrosion in aqueous solutions, particularly at non-neutral pHs, negative electrode potentials and highly positive electrode potentials. I will present our initial work to mitigate this issue, by tuning electrolyte composition, through the use of co-catalysts, and varying fabrication conditions to alter the structural morphology of the photoanodes. In preliminary results, the use of NiOOH co-catalysts, fabricated using the same facile CVD method, has increased the photocurrent density at 1.23 V RHE by 20%, left-shifted the onset potential, and suppressed the BiVO 4 degradation rate by three times compared to that of a WO 3 /BiVO 4 photoelectrode without NiOOH. This research seeks to elucidate challenges of developing upscaled materials for water splitting, to facilitate the pathway to commercially viable photoelectrochemical hydrogen production. References 1. Kafizas et al.; Journal of Physical Chemistry C; doi.org/10.1021/acs.jpcc.7b00533. 2. Belles et al.; Sustainable Energy & Fuels; doi.org/10.1039/C8SE00420J 3. Tam; PhD thesis, Imperial College London, London, 2022. 4. Moss et al.; Advanced Energy Materials ; doi.org/10.1002/aenm.202003286
5. Bedoya-Lora et al.; Frontiers in Chemical Engineering ; doi.org/10.3389/fceng.2021.749058 6. Bedoya-Lora et al.; Journal of Materials Chemistry A . doi.org/10.1039/C7TA05125E 7. Hankin et al.; Energy & Environmental Science ; doi.org/10.1039/C6EE03036J
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