Cu₂O Photocathodes with Bidirectional CuSCN Layers to Improve Charge Separation for Enhanced Photoelectrochemical Water Splitting

Cu2O has great potential as a photocathode for photoelectrochemical water splitting, and efficient charge separation through interface modulation is the key for potential application. In this work, we develop a facial strategy to maximally reduce the recombination of charge carriers via CuSCN in two directions, that is, E-CuSCN on an FTO substrate from ethylenediaminetetraacetic acid (EDTA) electrolyte as the hole-transport layer and D-CuSCN on the Cu2O layer from diethanolamine (DEA) electrolyte as the hole-storage layer. As a result, the E-CuSCN/Cu2O/D-CuSCN with efficient charge separation shows improved activity with a photocurrent density up to 5 mA·cm–2, which is 7 times higher than that of the pristine Cu2O. This work provides a new method for separating photocharges based on the design of interfacial crystal structure for high-efficiency photocathodes.