Insight into the role of sulfur in increasing intrinsic activity of Ni–Fe for efficient water splitting electrocatalysis

It is of great significance to explore and design low-cost and efficient electrocatalysts for the storage and conversion of intermittent renewable resources to clean hydrogen by water splitting. Herein, the amorphous Ni–Fe–S electrocatalysts are rapidly synthesized on Cu sheets and Ni foams using the simple electrodeposition method. After optimizing the S concentration, the Ni–Fe–S electrocatalysts exhibit the simultaneously boosted hydrogen and oxygen evolution reaction performances compared to the as-synthesized Ni–Fe and Ni. In addition, the Ni–Fe–S electrocatalysts as the bifunctional electrodes only require a cell voltage of 1.584 V (on Ni foam) and 1.705 V (on Cu sheet) to reach 10 mA/cm2 with excellent stability in the electrocatalytic activity and surface properties. The results exhibit that the enhanced electrocatalytic activity can be attributed to the role of the doped S in formatting the amorphous structure, improving the hydrophilic and aerophobic properties, optimizing the electronic structure as well as enhancing the electrochemically active sites. This work might offer a new insight into the design of the cheap and highly efficient electrodes for generation of hydrogen by water splitting.