CuInS Photocathodes with Atomic Gradation-Controlled (Ta,Mo)(O,S) Passivation Layers for Efficient Photoelectrochemical H Production.

An atomic gradient passivation layer, (Ta,Mo)(O,S), is designed to improve the charge transportation and photoelectrochemical activity of CuInS-based photoelectrodes. We found that Mo spontaneously diffused to the a-TaO layer during e-beam evaporation. This result indicates that the gradient profile of MoO/TaO is formed in the sublayer of (Ta,Mo)(O,S). To understand the atomic-gradation effects of the (Ta,Mo)(O,S) passive layer, the composition and (photo)electrochemical properties have been characterized in detail. When this atomic gradient-passive layer is applied to CuInS-based photocathodes, promising photocurrent and onset potential are seen without using Pt cocatalysts. This is one of the highest activities among reported CuInS photocathodes, which are not combined with noble metal cocatalysts. Excellent photoelectrochemical activity of the photoelectrode can be mainly achieved by (1) the electron transient time improved due to the conductive Mo-incorporated TaO layer and (2) the boosted electrocatalytic activity by Mo(O,S) formation.