An ‘enhancement-tandem effect’ induced by the ‘P vacancy–Cr dopant structure’ for optimizing the energy barrier and reaction pathway for alkaline HER

It is a challenge to enable non-precious metal-based electrodes to exceed the ultra-high alkaline HER activity of Pt-based precious metals by constructing a ‘vacancy–dopant structure’ with controllable vacancy concentration. Density functional theory (DFT) calculations revealed that the ‘P vacancy (Pv)–Cr dopant structure’ stimulates a significant enhancement-tandem effect during the alkaline HER process. This enhancement effect is reflected in enhanced conductivity and the adsorption capability of H2O and OH*, thereby reducing the reaction energy barrier. Simultaneously, the tandem effect induces the Cr dopant near Pv as a unique OH* adsorption site, thereby activating the Ni(Pv)–P–Cr(Pv) mechanism that effectively prevents the poisoning of Ni hydrophilic sites and optimizes the alkaline HER pathway. Based on these findings, Cr–NiPv/IF with the ‘Pv–Cr dopant structure’ was innovatively constructed using the ‘phosphorization-quenching’ technique. Interestingly, the quenching temperature difference is positively correlated with the Pv concentration. Under the enhancement-tandem effect of the ‘Pv–Cr dopant composite structure’, Cr–NiPv/IF only requires 240 mV to deliver 1 A cm−2 for alkaline HER, which is 3.04-fold higher than that of Pt/C@IF. This work offers a novel design concept for constructing non-precious metal-based electrodes that surpass the performance of Pt-based electrodes.