Nickel selenide as an efficient electrocatalyst for selective reduction of carbon dioxide to carbon-rich products

Abstract

Identifying new catalyst composition for carbon dioxide electroreduction to high-value products has been the center of attraction over the last several years. In this article, nickel selenide (NiSe₂) has been identified as a high-efficiency electrocatalyst for CO₂ electroreduction at neutral pH. Interestingly, NiSe₂ shows high selectivity towards specific reduction products, forming carbon-rich C2 products like ethanol and acetic acid exclusively at lower applied potential with 98.45% faradaic efficiency, while C1 products formic acid and carbon monoxide formed preferentially at higher applied potential. More importantly, the C2 products such as acetic acid and ethanol are obtained at very low applied potential, which further corroborates the novelty of this catalyst in CO₂ utilization with minimal energy expense. The NiSe₂ catalyst surface has been studied through density functional theory calculations which show that the adsorption energy of the CO intermediate on the NiSe₂ surface is optimal for extensive reduction through formation of C–C bonds but not strong enough for surface passivation, thus leading to high selectivity for C2 products. Such high efficiency of the catalyst can be a result of increased covalency of the selenide anion along with a high d-electron density of the Ni center. The hydrothermally synthesized NiSe₂ sample also shows high activity for oxygen evolution through electrocatalytic water splitting in alkaline medium, effectively making it a bifunctional catalyst which can lower the concentration of the atmospheric pollutant CO₂ while at the same time enriching the air with O₂.