Tunable fcc/hcp NiRu alloy nanoparticles anchored on hierarchical N-doped carbon nanosheets for enhanced hydrogen evolution.

Developing highly active, stable and low-cost electrocatalysts for the hydrogen evolution reaction (HER) is crucial for large-scale water electrolysis. Herein, we report a molecule-assisted assembly-pyrolysis strategy to construct hierarchical N-doped carbon nanosheets anchored with NiRu alloy nanoparticles (Ni5Ru@N-C) as a highly active and durable HER electrocatalyst. Strong coordination between iminodiacetonitrile (IDAN) and Ni/Ru ions forms a two-dimensional organometallic coordination polymer (OCP) precursor, which pyrolyzes into thin carbon-layer-encapsulated NiRu nanoparticles with controllable face-centered cubic (fcc) and hexagonal close-packed (hcp) phase, optimizing hydrogen adsorption and catalytic activity. The optimized fcc/hcp Ni5Ru@N-C exhibits an ultralow overpotential of 17 mV at 10 mA cm-2, fast HER kinetics with a Tafel slope of 32 mV dec-1 and excellent durability over 72 h, outperforming that of commercial Pt/C. Moreover, this catalyst demonstrates promising performance in practical two-electrode water electrolyzers. This work provides a molecular-assisted strategy for designing phase- and structure-controlled electrocatalysts for efficient hydrogen production.