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

Abstract

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 used in the electrocatalytic reduction reaction of CO₂ (CO₂RR) to CO due to its abundant reserves, low price, good stability and non-toxic. 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, pure ZnOHF sample was synthesized by hydrothermal method. The effect of heat treatment on the structure, texture and electrocatalytic CO₂RR performance of the samples was investigated. The electrocatalytic evaluation results revealed that the heat-treated ZnOHF sample showed better activity and CO selectivity compared with untreated sample. The Faraday efficiency of CO (FE_CO) reached 77.4% at −1.15V vs. RHE. Even at potential of −1.05 V vs. RHE, the current density and FE_CO could be stabilized at −6.17 mA/cm² and 72% in 5 h. This was because heat treatment optimized the amount of surface hydroxyl of ZnOHF. The microcrystalline particles became uniform and fine. The roughness and electrochemical surface area (ECSA) also increased, thus exposing more active sites and promoting the adsorption and activation of CO₂ as well as the desorption of CO. This study provides experimental basis and theoretical guidance for the design and development of Zn-based catalysts for electrocatalytic CO₂RR.