Heterostructural NiFeW disulfide and hydroxide dual-trimetallic core-shell nanosheets for synergistically effective water oxidation

A stable and highly active core-shell heterostructure electrocatalyst is essential for catalyzing oxygen evolution reaction (OER). Here, a dual-trimetallic core-shell heterostructure OER electrocatalyst that consists of a NiFeWS₂ inner core and an amorphous NiFeW(OH)_z outer shell is designed and synthesized using in situ electrochemical tuning. The electrochemical measurements of different as-synthesized catalysts with a similar mass loading suggest that the core-shell Ni_0.66Fe_0.17W_0.17S₂@amorphous NiFeW(OH)_z nanosheets exhibit the highest overall performance compared with that of other bimetallic reference catalysts for the OER. Additionally, the nanosheet arrays were in situ grown on hydrophilic-treated carbon paper to fabricate an integrated three-dimensional electrode that affords a current density of 10 mA cm⁻² at a small overpotential of 182 mV and a low Tafel slope of 35 mV decade⁻¹ in basic media. The Faradaic efficiency of core-shell Ni_0.66Fe_0.17W_0.17S₂@amorphous NiFeW(OH)_z is as high as 99.5% for OER. The scanning electron microscope, transmission electron microscope, and X-ray photoelectron spectroscopy analyses confirm that this electrode has excellent stability in morphology and elementary composition after long-term electrochemical measurements. Importantly, density functional theory calculations further indicate that the core-shell heterojunction increased the conductivity of the catalyst, optimized the adsorption energy of the OER intermediates, and improved the OER activity. This study provides a universal strategy for designing more active core-shell structure electrocatalysts based on the rule of coordinated regulation between electronic transport and active sites.