Time- and frequency-resolved operando XAS characterization of Co-Fe co-catalyst local structure on WO3/BiVO4 photoanodes

Metal oxides photoanodes, such as WO3/BiVO4 heterostructures, represent the state of the art towards photoelectrochemical 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, and operando XAFS analysis, mimicking the PEC illumination and bias conditions, demonstrated a powerful tool to probe the catalyst structural and electronic features in steady-state. However, as the catalytic site has limited lifetime before relaxation through charge transfer or recombination, sub-ms time resolution is required to probe it. Thus, time- and frequency- resolved operando PEC-XAFS measurements will provide a local structural basis for an understanding of the physical properties of this photocatalyst in real operating conditions, focusing on the structural dynamics of the catalyst upon modulation of the illumination source.