Sequential Multilayer Design with SnO2-Layer Decoration for Inhibiting Photocorrosion of Cu2O Photocathode

The Cu2O-based photocathode has been widely applied in photoelectrocatalytic hydrogen evolution and carbon dioxide reduction systems. However, the poor stability of Cu2O caused by photocorrosion highly restricts the application. In this work, a multilayer configuration is designed as Cu2O/ZnO/SnO2 via sequential depositions of electrodeposition and spin-coating. The liquid-phase epitaxial growths of the Cu2O and ZnO layers are achieved by sequential electrodepositions on a FTO/Au substrate. The decoration of a uniform SnO2 layer onto Cu2O/ZnO is realized by a SnO2 QDs coating and provides dual functions for boosted electron transfer and surface reaction. The protection of the SnO2 layer is fulfilled by the inhibition of Cu+ transformation, resulted from the compact covering of SnO2 QDs onto the exposed surface of the Cu2O and ZnO layers. Consequently, the enhanced photocurrent density and improved stability are obtained for Cu2O/ZnO/SnO2 compared to bare Cu2O and Cu2O/ZnO sample photocathodes. The necessary role of SnO2 QDs serving as electron transfer and protection layers studied in this work reveals the remarkable potential in the modification of other vulnerable electrode materials.