Indium-Induced Electronic Structure Engineering of In3Ni2/NiPx for Alleviating Kinetic Mismatch in Alkaline Hydrogen Evolution

Abstract

Developing efficient and sustainable energy conversion technologies is critical to global energy and environmental remediation. Electrocatalytic water splitting has emerged as a promising route for green hydrogen supply. Nevertheless, alkaline HER performance is greatly limited by sluggish water dissociation. An inherent kinetic mismatch persists between water activation and hydrogen evolution. Nickel phosphide (NiP_x) catalysts are widely investigated for alkaline hydrogen evolution reaction (HER). They possess favorable hydrogen adsorption capability and low fabrication cost. Herein, an In₃Ni₂/NiP_x catalyst was fabricated on CP via a one-step electrodeposition strategy. The catalyst delivers outstanding alkaline HER performance, requiring low overpotentials of 55 mV to achieve current densities of 10 mA cm⁻², respectively. Long-term stability is maintained within 210 h. XPS and EXAFS characterizations reveal that indium (In) introduction trigger significant electronic structure reconstruction and charge redistribution. Key intermediates including H*, OH* and H₂O* show optimized adsorption after In introduction. Water dissociation energy barrier is reduced to 0.78 eV. Hydrogen adsorption free energy is adjusted to a near-thermoneutral value of 0.02 eV. Heterometal modification offers a feasible strategy to tune reaction kinetics. It also provides a rational design route for high-performance alkaline HER catalysts.