NiCo alloys with optimized electronic structure for ultralow overpotential alkaline hydrogen evolution

Modulating the electronic structure of alloy catalysts is a pivotal strategy for enhancing their intrinsic hydrogen evolution reaction (HER) performance. This work demonstrates that incorporating cobalt into nickel can effectively modulate the electronic structure of nickel while leveraging the excellent lattice matching between Ni and Co to maintain alloy structural integrity, thereby simultaneously enhancing intrinsic HER activity and endowing the catalyst with superior structural stability. The optimized Co1Ni1/C catalyst exhibits an ultralow overpotential of 21.2 mV at 10 mA cm−2, which not only surpasses that of most reported NiCo alloys but also approaches the level of NiMo alloys, while effectively avoiding the common metal leaching issues associated with NiMo alloys. Systematic characterization using X-ray photoelectron spectroscopy and electron paramagnetic resonance proved that cobalt doping induces electron transfer from Ni to Co, raising the d-band center of Ni and increasing unpaired electron density. These electronic reconfigurations strengthen water adsorption at nickel active sites, thereby accelerating the water dissociation kinetics. The catalyst also exhibits superior stability with minimal performance decay during prolonged operation. The catalyst also demonstrates excellent stability with minimal performance degradation during prolonged operation, outperforming conventional NiMo alloys.