Efficient Water Splitting System Enabled by Multifunctional Platinum-Free Electrocatalysts

Tremendous research efforts have been focused on the development of a water splitting system (WSS) to harvest hydrogen fuels, but currently available WSSs are complicated and cost-ineffective mainly due to the applications of noble platinum or different electrocatalysts. Herein, a novel WSS comprising electricity generation from solar panels, electricity storage in rechargeable zinc-air batteries (ZABs), and water splitting in electrolyzers, enabled by hybrid cobalt nanoparticles/N-doped carbon embellished on carbon cloth (Co-NC@CC) as multifunctional platinum-free electrocatalysts is reported. Consequently, the Co-NC@CC electrode presents excellent trifunctional electrocatalytic activity with an onset potential of 0.94 V for oxygen reduction reaction, and an overpotential of 240 and 73 mV to achieve a current density of 10 mA cm(-2) for oxygen and hydrogen evolution reactions, respectively. For a proof-of-concept application, a rechargeable ZAB assembled from the high-performance Co-NC@CC air cathode exhibits a high open circuit potential of 1.63 V and a superior energy density of 1051 Wh kg(Zn)(-1). Furthermore, an overall water splitting electrolyzer constructed by the symmetrical Co-NC@CC electrodes delivers a current density of 10 mA cm(-2) at a low cell voltage of 1.57 V. Such a solar-powered WSS can harvest hydrogen day and night, demonstrating a potential for application in sustainable renewable energy.