Effect of heat treatment on the performance of ZnOHF for electrocatalytic reduction of CO₂ to CO

The selective and efficient conversion of inert CO₂ into value-added chemicals by electrochemical methods is one of the important ways to alleviate the environmental and energy crisis. Non-precious metal Zn is often studied in electrocatalytic CO₂ reduction reaction (CO₂RR) to CO because of its abundant reserves, low price and good stability. However, it is still necessary to improve the catalytic performance of traditional Zn-based catalysts for CO₂RR. In order to optimize the performance of Zn-based catalysts, the pure ZnOHF sample was synthesized by hydrothermal method. The effect of heat treatment on the structure, texture and electrocatalytic CO₂RR performance of ZnOHF samples was studied. The electrocatalytic evaluation results show that the heat-treated ZnOHF sample gives better CO₂RR activity and CO selectivity compared with untreated sample, the Faraday efficiency of CO (FE_CO) reaches 77.4% at −1.15V vs. RHE. And even at a potential of −1.05 V vs. RHE its current density and FE_CO can be stabilized at −6.17 mA/cm² and 72% in 5 h. This is because heat treatment can make the surface of ZnOHF obtain appropriate hydroxyl amount, the microcrystalline particles become uniform and fine, and the roughness and electrochemical specific surface area (ECSA) increase, thus exposing more active sites and promoting the adsorption and activation of CO₂ on the surface and CO desorption. This provides experimental basis and theoretical guidance for the design and development of Zn-based catalysts for electrocatalytic CO₂RR.