Efficient carrier transfer route via the bridge of C60 particle to TiO2 nanoball based coverage layer enables stable and efficient cadmium free GeSe photocathode for solar hydrogen evolution

Abstract Sufficient passivation/coverage and transfer of photoexcited carriers are the key factors in creating efficient and stable photoelectrochemical water splitting electrodes. In this work, the photoelectrochemical properties of Cd-free GeSe micro air brick-based photocathodes were systematically investigated by surface and interface analyses. It was found that carrier accumulation at the interface between Pt catalysts and the surface of the GeSe photocathode would induce the detachment of Pt catalysts and therefore degrade the photoelectrochemical current. Fortunately, we found that introducing a C60 particle intermediate helped build a bridge between the Pt catalysts and TiO2 balls, accelerating electron transfer, avoiding the self-reduction of TiO2 balls, and decreasing the accumulation of photoexcited carriers at interfaces. The GeSe micro air brick-based photocathode covered with Cd-free Pt/C60 pat.-TiO2 ball composite materials exhibited a significantly enhanced long-term stability of 60 h. Based on such a Pt/C60 pat.-TiO2 ball/GeSe photocathode, a GeSe-BiVO4 tandem cell for unbiased overall solar water splitting was first reported. The tandem cell presented a benchmark solar to hydrogen (STH) conversion efficiency of 1.37 % with appreciably long time stability over 12 h, indicating the great competitiveness of the GeSe-based photoelectrode among the emerging photoelectrodes for solar hydrogen evolution.