A p-type Cu2O Photoanode for Solar Water Oxidation

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 ITO layers as an electron-selective back contact, combined with Al2O3, Au, and Ni front layers, significantly enhanced the charge separation and electron transfer efficiency. 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—the highest reported for metal oxide photoanodes—while maintaining excellent stability over 30 hours. Moreover, the photoanode demonstrated remarkable photoelectrochemical performance under neutral pH conditions. 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.