Oxygen evolution reaction: the key to optimize photocatalytic water oxidation – OERKOP

Electrochemical reactions driving the solar water splitting process involve physico-chemical transformations of photoelectrodes generated by charge transfer at interface with the electrolyte. Oxygen evolution reaction (OER) at the photoanode is the main obstacle for achieving efficient hydrogen yield by solar water splitting. OERKOP project aims to understand the mechanisms underlying the OER, beyond the current state of the art, for two archetypal metal oxides used as photoanodes: Fe2O3 and BiVO4, both catalytically activated by oxyhydroxide catalysts (M-OOH, with M = Fe, Ni, Co, Cu, Zn). On the one hand, increasing the metal electronegativity (from Fe to Zn) will allow tuning the active sites involved in the OER and consequently the reaction intermediates and surface kinetics. On the other hand, comparing Fe2O3 and BiVO4 materials exhibiting significantly different holes conductivities, will allow confronting bulk electronic conduction to surface kinetics during the OER. To reach our goal, we propose to use a correlative operando approach combining multi-scale and multi-selective microscopy techniques: scanning transmission X-ray microscopy (STXM) and scanning transmission electron microscopy (STEM). These techniques will employ a common sample environment in a dedicated photoelectrochemical cell. STXM will allow measuring nanoscale, chemistry and chemical coordination at the metal oxide/oxyhydroxide catalyst and photoanode/electrolyte interfaces. STEM complement the spatial resolution limitation of the STXM (~50 nm) and allow addressing the structure and morphology at ~10 nm scale. DFT calculations will allow discerning complex effects and determining the reaction priorities of different photocatalytic sites. The project is articulated around eight working packages (WP), covering the whole scientific aspects, from the growth of the photoanodes to the methodology applied for the data analysis. Each WP has an identified leader. Several risks are identified, and alternative solutions foreseen whenever possible at this stage. OERKOP aims ultimately the success of a circular economy based on low carbon technologies using Earth abundant, eco-friendly photoactive and recyclable materials. Research herein will be the springboard to upgrade and develop appropriate engineering methods targeting the enhancement of both bulk and surface properties of the photoanodes for an optimized solar water splitting process.