Solar Driven 15.7% Hydrogen Conversion by Harmony of Light Harvesting, Electron Transporting Bridge, and S-Defection in a Self-Assembled Microscale CuS/rGO/CP Photoanode

Abstract

CuS is an encouraging photoelectrode candidate that meets the essential requirements for efficient solar-to-hydrogen production, but it has not been thoroughly studied. A CuS light absorber layer is grown by the self-assembly of copper and sulfur precursors on a carbon paper (CP) electrode. Simultaneously, rGO is introduced as a buffer layer to control the optical and electrical properties of the absorber. The well-ordered microstructural arrangement suppresses the recombination loss of electrons and holes owing to enhanced charge-carrier generation, separation, and transport. The potential reaching 10 mA cm−2 in 1.0 m KOH solution is significantly lowered to 0.87 V, and the photocurrent density at 1.23 V is 94.7 mA cm−2. The computational result reveals that the potential-determining step is sensitive to O* stability; the lower stability of O* in the thin layer of CuS/rGO decreases the free-energy gap between the initial and final states of the potential-determining step, resulting in a lowering of the onset potential. The faradaic efficiency for the photoelectrochemical oxygen evolution reaction in the optimized 2CuS/1rGO/CP photoanode is 98.60%, and the applied bias photon-to-current and the solar-to-hydrogen efficiencies are 11.2% and 15.7%, respectively, and its ultra-high performance is maintained for 250 h. These record-breaking achievement indices may be a trigger for establishing a green hydrogen economy.