Crystal Face Dependence of p-Cu[sub 2]O Stability as Photocathode

Previously we hypothesized that the reported stability of electrodeposited films is attributed to the predominant -terminated (111) surface, where the -supported reduction occurs and the -assisted reduction, which is the decomposition of , does not happen. The well-known instability of single-crystal is attributed to predominant (211) and (311) surfaces, where the photodecomposition into Cu is inevitable at the exposed sites. To examine our hypothesis, the stability and photochemical behavior were compared between electrodeposited films with predominantly -terminated surfaces and ones with predominantly -terminated surfaces. When used as photocathodes, the predominantly -terminated films did not deteriorate as readily as the predominantly -terminated films did. Also, when oxygen was removed from the aqueous solution, the predominantly -terminated films generated photocurrents one order of magnitude smaller compared to the predominantly -terminated films, indicating the stability of the -terminated surface against photodecomposition into Cu. These results confirmed our hypothesis on the crystal face dependence of stability as a photocathode.