Developing BiVO 4 -based photoelectrochemical water splitting devices using chemical vapour deposition Andreas Kafizas 1,4 , Brian Tam 1,2 , Zachary Feng 1 , Ryan Lai 1 , Christos Krigkou 1 , Yuqi Chen 1 , Jenny Nelson 2 , George Creasey 3 , Anna Hankin 3 1 Department of Chemistry, Imperial College London, UK, 2 Department of Physics, Imperial College London, UK, 3 Department of Chemical Engineering, Imperial College London, UK, 4 The London Centre for Nanotechnology, Imperial College London, UK Current H 2 demands are vast, with the industry valued in excess of $100 billion. Today, most H 2 is produced from the non-renewable reformation of natural gas, and accounts for ~3% of total CO 2 emissions. 1 Various renewable methods of producing H 2 are being developed, with solar-driven photoelectrochemical (PEC) water splitting one of the most promising routes in terms of efficiency and potential cost. 2 Bismuth vanadate (BiVO 4 ) has emerged as one of the most promising candidates for use as a photoanode in PEC water splitting devices. 3 State-of-the-art systems have achieved solar-to-hydrogen (STH) efficiencies above 8%; 4 nearing benchmark efficiencies for commercial viability. 5 However, for this technology to reach commercial maturity, prototypes need to be demonstrated on a scale commensurate to their intended application. 6 In this talk, I will present the work we have done in my group on the development of scalable synthetic routes to high performance BiVO 4 -based photoanodes (Figure 1a), using chemical vapor deposition (Figure 1b). I will also show how the intrinsic charge carrier behavior in these photoanodes was studied using in operando time- resolved optical spectroscopies to reveal the kinetics of water oxidation, and insight on the rate-limiting step in the reaction mechanism. Lastly, I will present the work we have done on developing PEC water splitting prototypes, incorporating BiVO 4 -based photoanodes ~50 cm 2 in size (Figure 1c).
Figure 1: (a) Incident photon-to-current efficiencies seen at 1.23 V vs RHE for an optimised BiVO4-based photoanode in a neutral buffered electrolyte, (b) the CVD reactor used to produce moderate scale photoanodes (~50 cm2 in size) and (c) the PEC water splitting prototype in action. References 1. IEA. Hydrogen - Fuels & Technologies . (2020). Moss, B., Babacan, O., Kafizas, A. & Hankin, A. A Review of Inorganic Photoelectrode Developments and Reactor Scale-Up Challenges for Solar Hydrogen Production. Adv. Energy Mater. 2003286 , 1–43 (2021). 2. Park, Y., McDonald, K. J. & Choi, K.-S. Progress in bismuth vanadate photoanodes for use in solar water oxidation. Chem. Soc. Rev. 42 , 2321–2337 (2013). 3. Pihosh, Y. et al. Photocatalytic generation of hydrogen by core-shell WO3/BiVO4 nanorods with ultimate water splitting efficiency. Sci. Rep. 5 , 11141 (2015). 4. Hammarström, L. & Durrant, J. Mission Innovation Challenge ‘Converting Sunlight’ . (2017). Kim, J. H., Hansora, D., Sharma, P., Jang, J. W. & Lee, J. S. Toward practical solar hydrogen production-an artificial photosynthetic leaf-to-farm challenge. Chem. Soc. Rev. 48 , 1908–1971 (2019).
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