Defect engineering of Ni3S2 nanosheets with highly active (110) facets toward efficient electrochemical biomass valorization

Abstract

Defect engineering has emerged as a powerful strategy to modulate the surface electronic structure of transitional metal based electrocatalysts, which would tune the adsorption behaviors towards reaction intermediates and thus boost the catalytic activity. In this paper, an array of sulfur vacancy-rich Ni₃S₂ nanosheets (V_s-Ni₃S₂) grown in situ on a Ni foam substrate is facilely prepared and employed as a catalytic electrode for electro-oxidation of benzyl alcohol (BA). The defective catalyst has more favorable reaction dynamics with respect to the competitive water oxidation reaction at the anode. A much higher peak current density of 94.2 mA cm⁻² and a smaller Tafel slope of 48.15 mV dec⁻¹ are obtained in 1.0 M KOH containing 30 mM BA. Electrolysis results reveal a 100% conversion of BA, 97.8% yield of benzoic acid and ∼100% faradaic efficiency at a relatively low potential (1.325 V vs. RHE), revealing superior energy conversion efficiency. First-principles density functional theory (DFT) results disclose that the availability of sulfur vacancies modulates the electronic conductivity of V_s-Ni₃S₂ and optimizes the adsorption energy capability towards intermediate products, thus facilitating fast redox reaction kinetics. The work should shed light on the rational design of advanced defective electrocatalysts for biomass valorization.