Hydrogen-evolving photocathodes consisting of Cu2SnxGe1−xS3 particles synthesized by polymerized complex method and sulphurization

Abstract

A facile, scalable approach to synthesizing Cu₂Sn_xGe_1−xS₃ (CTGS) photocatalytic particles was developed, based on the sulphurization of particulate oxide precursors prepared by a polymerized complex (PC) method. The combination of this PC technique and sulphurization enabled the synthesis of relatively small CTGS particles having more uniform size distributions compared with materials produced using a conventional solid-state reaction (SSR). Consequently, a photocathode consisting of CTGS particles synthesized by the PC method followed by sulphurization exhibited superior photoelectrochemical (PEC) performance during hydrogen evolution relative to that of specimens synthesized via the SSR. The effects of the Sn/Ge ratio and of Cu deficiency on the crystalline structure, optical properties and PEC performance of CTGS particles synthesized by the PC technique and sulphurization were elucidated. A photocathode consisting of Cu_1.94Sn_0.5Ge_0.5S₃ (Sn/(Sn + Ge) = 0.5, 3% Cu deficient) particles showed the highest hydrogen evolution performance among the present specimens, providing a photocurrent of −8.1 mA cm⁻² at an applied potential of 0 V vs. a reversible hydrogen electrode (RHE) under simulated sunlight and a 0.59% half-cell solar-to-hydrogen conversion efficiency at 0.15 V_RHE.