Key Strategies on CuO Photocathodes toward Practical Photoelectrochemical Water Splitting.

Cuprous oxide (CuO) has been intensively in the limelight as a promising photocathode material for photoelectrochemical (PEC) water splitting. The state-of-the-art CuO photocathode consists of a back contact layer for transporting the holes, an overlayer for accelerating charge separation, a protection layer for prohibiting the photocorrosion, and a hydrogen evolution reaction (HER) catalyst for reducing the overpotential of HER, as well as a CuO layer for absorbing sunlight. In this review, the fundamentals and recent research progress on these components of efficient and durable CuO photocathodes are analyzed in detail. Furthermore, key strategies on the development of CuO photocathodes for the practical PEC water-splitting system are suggested. It provides the specific guidelines on the future research direction for the practical application of a PEC water-splitting system based on CuO photocathodes.