Metallic Ni3N nanosheets with exposed active surface sites for efficient hydrogen evolution

Abstract

Ni-Based catalysts have been considered as promising non-noble-metal hydrogen evolution reaction (HER) electrocatalysts for future clean energy devices. Here, atomically thin metallic Ni₃N nanosheets are fabricated as the hydrogen evolution cathode, which exhibit remarkable HER activity close to that of a commercial Pt/C electrode. The Ni₃N nanosheet catalyst shows an electrocatalytic current density of 100 mA cm² at a low overpotential of 100 mV vs. RHE, a high exchange current density of 0.32 mA cm⁻², a Tafel slope of 59.79 mV dec⁻¹ and remarkable durability (little activity loss >5000 cycles) in acidic media as well as high HER activity in neutral and alkaline media. Through systematic theoretical calculations, the active surface sites of the Ni₃N nanosheets are explicitly identified. The Ni atoms accompanied by surrounding N atoms on the N–Ni surface demonstrate a small ΔG_H* of 0.065 eV due to the Ni–N co-effect, which act as the most active HER sites. This finding broadens our vision to realize the HER activity of 2D metallic electrocatalysts and paves the way for exciting opportunities in exploring and optimizing advanced catalysts for future energy production.