Construction of Polarized Carbon-Nickel Catalytic Surfaces for Potent, Durable, and Economic Hydrogen Evolution Reactions.

Electrocatalytic hydrogen evolution reaction (HER) in alkaline solution is hindered by its sluggish kinetics toward water dissociation. Nickel-based catalysts, as low-cost and effective candidates, show great potentials to replace platinum (Pt)-based materials in the alkaline media. The main challenge regarding this type of catalysts is their relatively poor durability. In this work, we conceive and construct a charge-polarized carbon layer derived from carbon quantum dots (CQDs) on NiN nanostructure (NiN@CQDs) surfaces, which simultaneously exhibit durable and enhanced catalytic activity. The NiN@CQDs shows an overpotential of 69 mV at a current density of 10 mA cm in a 1 M KOH aqueous solution, lower than that of Pt electrode (116 mV) at the same conditions. Density functional theory (DFT) simulations reveal that NiN and interfacial oxygen polarize charge distributions between originally equal C-C bonds in CQDs. The partially negatively charged C sites become effective catalytic centers for the key water dissociation step via the formation of new C-H bond (Volmer step) and thus boost the HER activity. Furthermore, the coated carbon is also found to protect interior NiN from oxidization/hydroxylation and therefore guarantees its durability. This work provides a practical design of robust and durable HER electrocatalysts based on nonprecious metals.