Key Strategies on Cu 2 O Photocathodes toward Practical Photoelectrochemical Water Splitting.

Cuprous oxide (Cu 2 O) has been intensively in the limelight as a promising photocathode material for photoelectrochemical (PEC) water splitting. The state-of-the-art Cu 2 O 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 Cu 2 O layer for absorbing sunlight. In this review, the fundamentals and recent research progress on these components of efficient and durable Cu 2 O photocathodes are analyzed in detail. Furthermore, key strategies on the development of Cu 2 O 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 Cu 2 O photocathodes.