Dual Active Center-Assembled Cu₃₁S₁₆-Co_9-NiS₈ Heterodimers: Coherent Interface Engineering Induces Multihole...

The design of low-cost yet highly efficient electrocatalysts plays a critical role in energy storage and conversion reactions. The oxygen evolution reaction (OER) is considered a bottleneck of electrochemical water splitting for hydrogen fuel generation. It is still challenging to extract a high density of charge carriers in noble-metal-free alternative catalysts to facilitate sluggish kinetics. Herein, we report the rational design and coherent interface engineering for combining light-harvesting Cu₃₁S₁₆ with electroactive Co_9-NiS₈ (x = 0-9) to form novel Cu₃₁S₁₆-Co_9-NiS₈ heterodimers. By delicately controlling the kinetic growth in a seed-mediated growth method, the bifunctional centers, even with two distinct crystal phases, were integrated into a synergistic architecture, which achieved full-spectrum solar energy capture and light conversion to drive and activate the electrochemical reaction. Benefiting from the well-defined structure, high-quality interface, oriented attachment, and optimal Co/Ni bimetal ratio, Cu₃₁S₁₆-Co_7.2Ni_1.8S₈ produces a dramatically reduced overpotential (242 mV at 10 mA cm^-2) with a shift of 83 mV under visible-light excitation, achieving a 4.5-fold higher turnover frequency than that of its unirradiated Co_7.2Ni_1.8S₈ counterpart. This enhanced performance also far exceeds commercial RuO₂ (358 mV at 10 mA cm^-2) and most nonprecious-metal nanocatalysts. Further mechanistic studies reveal that coherent interface engineering leads to a strong photo/electricity coupling effect and efficient spatial charge separation, which induces sufficient hot holes that eventually accumulate at the electroactive sites to accelerate the multihole-involved OER. This work would open up new opportunities for the fabrication of non-noble metal electrocatalysts and management of charge carriers.