Coordination engineering of nickel sites in Ni-MOF for synergistic optimization of electronic structure and interfacial water toward efficient alkaline hydrogen evolution

Abstract

Alkaline water electrolysis is a highly promising method for green hydrogen production. However, the sluggish kinetics of the hydrogen evolution reaction (HER), particularly the high energy barrier associated with the water dissociation step (Volmer step), severely limit its overall efficiency. Metal–organic frameworks (MOFs), featuring well-defined active sites and tunable compositions and structures, serve as an ideal platform for investigating how the local microenvironment of metal sites governs their catalytic activity. This work reports an atomic-level coordination engineering strategy. By modulating the synthesis conditions to tailor the coordination environment of metal sites in Ni-MOFs, we regulate their electronic structure and interfacial water behavior. The synthesized Ni-N4-MOF exhibits outstanding catalytic activity in 1 M KOH, requiring a low overpotential of only 363 mV to achieve a current density of 10 mA cm⁻², with a Tafel slope of 104 mV dec⁻¹. This performance surpasses that of most reported non-precious-metal-based MOF catalysts. Furthermore, the catalyst exhibited excellent performance stability, showing only 4.8% voltage increase during a 200 hours continuous operation test at a constant current density of 10 mA cm⁻². Combined theoretical and experimental studies reveal that the enhanced HER performance of Ni-N4-MOF originates primarily from an accelerated Volmer step at the Ni sites. This acceleration is achieved by promoting the adsorption and dissociation of free water, optimizing the adsorption behavior of reaction intermediates, and modulating interfacial water behavior. This work provides important insights for designing high-performance alkaline HER electrocatalysts through precise engineering of the local coordination environment.