Sn-Ni 3 S 2 Ultrathin Nanosheets as Efficient Bifunctional Water-Splitting Catalysts with a Large Current Density and Low Overpotential.

Ni ₃ S ₂ nanosheets doped with tin (Sn) grown on nickel foam (Sn-Ni ₃ S ₂ /NF) through a facile hydrothermal process were found to be superior water-splitting electrocatalysts. As for overall water splitting (OWS), when the current density is 10 mA cm ^-2 , the required voltage is only 1.46 V. Meanwhile, it exhibits a large current density property and long-time stability (>60 h current-time tests) for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). In order to reach the current densities of 100 and 1000 mA cm ^-2 , Sn-Ni ₃ S ₂ /NF needs overpotentials of 0.17 and 0.57 V for HER, and 0.27 and 0.58 V for OER, respectively. The water-splitting property of Sn-Ni ₃ S ₂ /NF is much better than that of pure Ni ₃ S ₂ /NF or even 20 wt % Pt/C/NF and RuO ₂ /NF. Furthermore, Sn-Ni ₃ S ₂ /NF showed a higher turnover frequency at different potentials, with ∼100% Faraday efficiency for both O ₂ and H ₂ . The improved activity of Sn-Ni ₃ S ₂ /NF activity for water-splitting is attributed to the doping of Sn, which enhanced the intrinsic activity of Sn-Ni ₃ S ₂ /NF for OWS. This article not only provides a new efficient and stable catalyst for OWS, but also proposes an interface design principle for NF-based high-performance water-splitting materials.