Interface Engineering\nInduced by Low Ru Doping in\nNi/Co@NC Derived from Ni-ZIF-67 for Enhanced Electrocatalytic Overall\nWater Splitting

Electrochemical water splitting is a promising approach\nfor hydrogen\nevolution reactions (HER); however, the oxygen evolution reaction\n(OER) remains a major bottleneck due to its high energy requirements.\nHigh-performance electrocatalysts capable of facilitating HER, OER,\nand overall water splitting (OWS) are highly needed to improve OER\nkinetics. In this work, we synthesized a trimetallic heterostructure\nof Ru, Ni, and Co incorporated into N-doped carbon (denoted as Ru/Ni/Co@NC)\nby first synthesizing Ni/Co@NC from Ni-ZIF-67 polyhedrons via high-temperature\ncarbonization, followed by Ru doping using the galvanic replacement\nmethod. Benefiting from increased active surface sites, modulated\nelectronic structure, and enhanced interfacial synergistic effects,\nRu/Ni/Co@NC exhibited exceptional electrocatalytic performance for\nboth HER and OER processes. The optimized Ru/Ni/Co@NC catalyst, with\na minimal Ru mass ratio of ∼2.07%, demonstrated significantly\nlow overpotential values of 34 mV for HER and 174 mV for OER at a\ncurrent density of 10 mA/cm<sup>2</sup> with corresponding Tafel slope\nvalues of 33.42 and 34.39 mV/dec, respectively. Further, the optimized\ncatalyst was loaded onto carbon paper and used as anode and cathode\nmaterials for alkaline water splitting. Interestingly, a low cell\nvoltage of just 1.44 V was obtained. The enhanced electrolytic performance\nwas further elaborated by density functional theory (DFT) calculations,\nwhich confirmed that Ru doping in Ni/Co introduced additional active\nsites for H*, enhancing adsorption/desorption abilities for HER (Δ<i>G</i><sub>H*</sub> = −0.30 eV), lowering water dissociation\nbarrier (Δ<i>G</i><sub>b</sub> = 0.49 eV) and reducing\nthe energy barrier for the rate-determining step of OER (O* →\nOOH*) to 1.62 eV in an alkaline environment. These findings reflect\nthe significant potential of ZIF-67-based catalysts in energy conversion\nand storage applications.