Will Cuprous Oxide Really Make It in Water-Splitting Applications?

For cost-effective solar hydrogen production on an industrial scale, Earth-abundant, low-cost, and easily processable materials are required. In this Perspective, a case is made that cuprous oxide has strong potential for practical large-scale water splitting. Recent research directions for improved efficiency and durability are highlighted, which target both the back and front interfaces of the Cu2O light absorber as well as protective overlayers and co-catalysts. The translation of high-efficiency thin-film device architectures to photocatalytic sheets or particles is proposed as a disruptive approach to solar hydrogen generation with fertile ground for new scientific discoveries.