Controlling edge active-sites by vulcanizing bimetallic hydroxide for boosting oxygen evolution reaction

Abstract

Sulfur-laden wastewater can be served as a valuable resource to synthesize transition metal sulfides (TMSs) electrocatalysts to address the sluggish kinetics of oxygen evolution reaction (OER) in water splitting, which is a significant issue for environmental and energy advancements. However, TMSs are beset with intrinsic constraints, particularly their prevalence of catalytically inert basal planes that impede their efficacy. To solve this issue, herein, CoNi-S/CoNi(OH)2 nanosheets on nickel foam (NF) was constructed employing sodium ethyl xanthate (synthesized using sulfur-containing wastewater) to partially vulcanize CoNi(OH)2 for improving OER performance. In-situ formed Co9S8-Ni3S2 on CoNi(OH)2 nanosheets provides high density edge active sites, compensating for inert basal planes. Due to the bridging effects of S2– and O2–, the electronic redistribution is conducive to form Ni3+, thereby facilitating the phase transformation from CoNi-S/CoNi(OH)2 into active S-containing CoNiOOH. Density functional theory calculation verifies that incorporating S into CoNi(OH)2 leads to rich edge-catalytic sites and modulates the adsorption/desorption of oxygen-containing intermediates, significantly reducing the energy barriers of potential-determining step during OER process. Additionally, the stability of CoNi-S/CoNi(OH)2 has been enhanced by the strengthened M-S (M=Co, Ni) bonds via the π donation of Mn+ with S2– and O2–. All these endow CoNi-S/CoNi(OH)2 the low overpotential of 295 mV at 20 mA cm–2 with a Tafel slope of 58 mV dec–1. This work presents a strategy for utilizing sulfur-containing wastewater in clean energy applications.