High performance multicomponent bifunctional catalyst for overall water splitting
Designing highly active bifunctional electrocatalysts from Earth-abundant elements have great prospects in substituting precious-metal based catalysts for energy conversion processes, such as water splitting. Here, we report a bifunctional catalyst comprising transition metal hydroxides (TMOHs) and transition metal sulphide (TMS) grown onto a nickel foam (NF) surface, denoted NiFeOH/CoSx/NF, that delivers high electrocatalytic activity for both oxygen evolution reaction (OER: Ultra-low overpotential of 211 mV at a current density of 50 mA cm-2) and hydrogen evolution reaction (HER: Overpotential of 146 mV at a current density of 10 mA cm-2) in alkaline media, representing one of the best bifunctional catalytic performance yet reported for a non-noble metal based system. From our experimental observations, the significant improvement of the catalytic activity emanates from the synergistic effects of NiFeOH and CoSx, due to the optimization of their electronic configurations, thereby creating novel characteristics. Employing this catalyst system as both anode and cathode for overall water splitting in a water electrolyzer, delivers 10 mA cm-2 at low cell potential of 1.563 V with excellent long-term electrocatalytic functionalities over 10 h of continuous operation. These findings represent the design principle for developing multi-component bifunctional electrocatalyst for overall water splitting.