Bifunctional CdS@Co9S8/Ni3S2 catalyst for efficient electrocatalytic and photo-assisted electrocatalytic overall water splitting

Abstract

The production of green hydrogen energy from water splitting driven by electric or solar energy is of great interest nowadays. The development of highly efficient, stable, and noble-metal-free bifunctional electrocatalysts has sparked a huge surge in investigation in the field of electrocatalytic (EC) water splitting. Herein, an original 1D core@2D branch CdS@Co₉S₈/Ni₃S₂ electrode is prepared in situ on Co/Ni alloy foam through a simple one-pot hydrothermal process. The binder-free, self-supported CdS@Co₉S₈/Ni₃S₂ is demonstrated to be a low-cost and highly efficient bifunctional electrocatalyst for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline solution. The optimal CdS@Co₉S₈/Ni₃S₂ electrode exhibits excellent bifunctional HER and OER properties with quite low overpotentials of 69.6 and 285 mV required to reach EC currents of −10 and 20 mA cm⁻², respectively. Moreover, using the CdS@Co₉S₈/Ni₃S₂ electrode as both the anode and cathode, the assembled electrolyzer only required a 1.56 V cell voltage to reach a current density of 10 mA cm⁻². Significantly, it was also found that such a metal foam-supported photocatalyst/electrocatalyst electrode can effectively realize dual model incorporated photo-assisted electrocatalytic overall water splitting, which delivers a 174.1% higher H₂ production rate than that of electrocatalysis only. This work may open a new avenue for the synergistic use of solar energy and electric energy in the production of hydrogen from water splitting.