Electronic structure modulation in Ni(OH)₂/NiMoO₄ n-n heterojunctions for enhanced alkaline hydrogen evolution

Designing heterojunction electrocatalysts with optimized electronic configurations is crucial for improving the performance of the hydrogen evolution reaction (HER), yet achieving precise regulation of charge transfer and reaction kinetics remains challenging. Here, we constructed an n-n heterojunction (NNM) consisting of Ni(OH)₂ and NiMoO₄ to modulate the electronic structure of NiMoO₄ by inducing a built-in electric field through the difference in Fermi energy poles. The optimized heterojunction exhibited excellent HER activity with an overpotential of only 69 mV at a current density of 100 mA cm −2 in 1.0 M KOH and a Tafel slope of 48.6 mV dec −1 , which was superior to most of the non-precious metal catalysts. Notably, the introduction of Ni(OH)₂ makes the catalyst superhydrophilic. The construction of heterojunction shifted the rate-determining step (RDS) from Volmer to Heyrovsky, which accelerated the reaction kinetics. Experiments and analyses showed that the enhanced catalytic activity promoted interfacial charge transfer. The catalyst maintained excellent stability for more than 100 h even under high current (2 A cm −2 ) conditions. In addition, the catalyst showed excellent performance in a simulated alkaline seawater environment, thus demonstrating its potential for industrial applications and providing a general strategy for the design of high-performance n-n heterojunction electrocatalysts.