Closely Arranged 3D–0D Graphene–Nickel Sulfide Superstructures for Bifunctional Hydrogen Electrocatalysis

Electrocatalysts with both dense active sites and abundant transport channels are crucial for the realization of high activity and fast kinetics in electrochemical applications but are very challenging to produce. Here, we illustrate a gas-emission-assisted synthetic strategy to produce such a hybrid architecture constructed by closely arranged 0D nickel sulfide nanodots (～9 nm) in a 3D porous graphene framework. Owning to these remarkable features, the material demonstrates superior electrocatalytic performance toward both hydrogen evolution (HER) and oxidation reactions (HOR). For HER, it requires a small overpotential of 105 mV to achieve a current density of 10 mA cm–2, features favorable kinetics with a Tafel slope of 42 mV dec–1, and survives for at least 50 h. For HOR, it needs a low overpotential of 46 mV for achieving 5 mA cm–2 and has strong durability for operation of 12 h