Operando Photoelectrochemical XAFS analysis of mixed Co-Fe co-catalysts on WO3/BiVO4 photoanodes.

Metal oxides photoanodes, such as WO3/BiVO4 heterostructures, represent the state of the art towards photoelectrochemical (PEC) water splitting, but their efficiency is still hampered by the sluggish oxygen evolution reaction (OER) kinetics and limited charge separation efficiency. Mixed Cobalt-Iron co-catalysts proved to be effective to temper such issues, however, a full comprehension of the catalytic cycle underlying such enhancement is yet to be achieved. To address this issue, we request beamtime to perform operando PEC-XAFS measurements, as a follow-up study to a previous beamtime at ESRF beamtime LISA BM-08. This experiments highlighted a structure-dependent response of the Co – Kedge upon bias and light stimuli, requiring further investigation. The present proposal aims to strenghten the understanding of the physical properties of this photocatalyst in real operating conditions, focusing on the Fe – Kedge behaviour and the dependence on the illumination source power.