Enhancing Overall Water Splitting via Anion and Cation Synergistical Modulation in NiS Amorphous Compound

Designing and synthesizing cost-effective catalysts that exhibit excellent performance of both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is a formidable task in the field of electrocatalysis. Herein, we present a Fe- and P-codoped NiS amorphous film catalyst (FeNiSP) via meticulous control over the cations and anions of metal compounds. The doped Fe and P increases active sites, reduces charge transfer resistance, and modulates electronic structures of the NiS matrix. Leveraging these advantages, the FeNiSP showcases exceptional bifunctional activities of HER and OER, with remarkably low overpotentials of only 135 and 330 mV for achieving a current density of 100 mA·cm^-2 during HER and OER, respectively. Additionally, a low cell voltage of 1.56 V at 10 mA·cm^-2 was achieved when it was employed as both the anode and the cathode for water splitting. Finally, density function theory calculations further elucidate that the simultaneous presence of Fe and P in the NiS amorphous film catalyst leads to a decrease in the band center of S and Ni. This consequential effect maintains a balanced adsorption/desorption of protons and strengthened the adsorption of O-based intermediates on the surface of FeNiSP, subsequently contributing to the outstanding electrocatalytic HER and OER activities.