Partially delocalized charge in crystalline Co-S-Se/NiO nanocomposites for boosting electrocatalytic oxygen evolution

Although reasonably specified and adjustable preparation of nanostructures with specific morphologies, ordered chemical compositions and electronic structures involving advanced energy chemistries is an important research area, high-efficiency, stable, and low-cost electrocatalysts for water splitting are greatly desirable and challenging. In this study, partially delocalized Co-S-Se ultra-thin nanosheets are obtained via a liquid-liquid interface-mediated strategy at an oil-water interface. These Co-S-Se ultra-thin nanosheets exhibit different-sized lamellar structures and have an average thickness of 0.83 nm. The ternary ultra-thin Co_0.45S_0.38Se_0.17 nanosheets demonstrate excellent performance for the OER, accompanied by an overpotential of 290 mV (1.52 V vs. RHE) at 10 mA cm^-2, and a Tafel slope of 74.5 mV dec^-1. In the meantime, the catalyst recombined with a stoichiometry NiO catalyst to form a composite interface, which also exhibited a good OER performance, with an overpotential of 260 mV at 10 mA cm^-2 and a smaller Tafel slope of 53.9 mV dec^-1. The nanosheets can rearrange the electronic density near the metal catalytic centers and increase the electron transfer. DFT calculations indicate that the partially delocalized charges can improve electrocatalytic performances, demonstrating modulated electroreduction properties. Due to the special atomic and electronic structure of the ternary transition metal alloy chalcogenide, the compound has great potential for energy storage, which will help in the rational design and synthesis of high-efficiency electrocatalysts.