Ni–OH promoted water dissociation on Pt/Ni dual active sites for accelerated alkaline hydrogen evolution

Abstract

Although Pt–M (M = transition metal) catalysts are indispensable for the hydrogen evolution reaction (HER), the key function and operative mechanism of M that extend beyond the electronic modulation of Pt remain poorly defined. To address this gap, we synthesized three-dimensional PtNi multibranched nanostructures (PtNi MBNs) incorporating dual active sites. In situ spectroscopic analyses reveal that Ni sites directly facilitate water dissociation through the generation of Ni–OH species, thereby producing ample H* intermediates that mitigate the hydrogen scarcity in alkaline electrolytes and subsequently enhance the formation of Pt–H bonds. Molecular dynamics simulations further confirm strong spontaneous bonding between Ni and O at the atomic scale, underscoring the critical role of Ni in driving water dissociation and stabilizing Ni–OH bonds. Such Pt/Ni dual-active-site mechanism endows the PtNi MBNs with exceptional performance in 1 M KOH, delivering an ultralow overpotential of 9.29 mV at 10 mA cm⁻² (35.2 mV lower than Pt/C) and a high mass activity of 9.30 A mg_Pt⁻¹ at −70 mV (3.63 times that of Pt/C). Characterization after cycling confirmed that PtNi MBNs exhibit excellent structural stability and electrochemical stability. This study advances the fundamental understanding beyond single site catalytic mechanisms and offers new insights for accelerating HER kinetics in alkaline electrolytes.