A p-type Cu2O photoanode for solar water oxidation

<h2>Summary</h2> The development of efficient, stable, and earth-abundant photoanodes for solar water oxidation is critical to advancing photoelectrochemical and photocatalytic systems for large-scale renewable fuel production. Here, we demonstrate that p-type Cu₂O, typically studied as a photocathode material, can be used as a high-performance photoanode through judicious engineering of charge carrier-selective contacts on thermally oxidized Cu₂O sheets. The introduction of Ga₂O₃, TiO₂, and indium tin oxide (ITO) layers as an electron-selective back contact, combined with Al₂O₃, Au, and Ni front layers, significantly enhanced charge separation and electron transfer. The champion Cu₂O photoanode exhibited a photocurrent density of 8.65 mA cm⁻² at 1.23 V vs. the reversible hydrogen electrode in alkaline media, which is the highest reported for metal oxide photoanodes. These findings highlight the pivotal role of charge carrier-selective interface engineering in broadening the scope of available semiconductor materials for photo(electro)catalytic oxidation reactions, irrespective of the doping type of the light-absorbing material.