Boosting the Solar Water-Splitting Performance of a CuO Photocathode via Synergetic Interfacial Hole Extraction and Surface Electron Collection

Abstract

P-type cupric oxide (CuO) is a promising photocathode material for solar hydrogen production, whereas its practical application is severely limited by constrained photoelectrochemical (PEC) performance and poor photostability. Herein, an integrated NiO/CuO/CuS photocathode has been developed, in which an ultrathin NiO interlayer is introduced at the back contact for hole extraction, and the CuS nanosheets, derived from CuO via in situ ion exchange, function as an active co-catalyst to promote surface water reduction. Benefiting from the synergistic integration of NiO and CuS, the integrated NiO/CuO/CuS photocathode exhibits a photocurrent density of –5.5 mA cm–2 at 0.4 V vs the reversible hydrogen electrode under AM 1.5G illumination, representing a two-fold enhancement compared to pristine CuO. Comprehensive experimental and theoretical results verify that the enhanced PEC performance can be mainly attributed to accelerated hole transport, suppressed bulk charge recombination, promoted electron utilization for hydrogen evolution, and increased light absorption. Furthermore, unassisted solar overall water splitting was achieved by coupling the optimal integrated photocathode with a TiO2-based photoanode in a wired configuration, delivering a high solar-to-hydrogen efficiency of 0.51%. This work provides an effective synergetic interface engineering strategy for designing high-performance photoelectrodes toward solar hydrogen production.