Electrochemical CO2 reduction on copper nanoparticles-dispersed carbon aerogels

Abstract

The conversion of CO₂ into carbon-based fuels via electrochemical reduction is a promising approach to realizing the termination of carbon cycling. Copper (Cu⁰) is considered to be an effective electrochemical catalyst for such purpose. However, it is limited by its instability and low selectivity. In this work, Cu²⁺ was embedded into a polycondensation structure of resorcinol (R) and formaldehyde (F) via sol-gel reaction, and the complex was then calcined at high temperature to obtain copper nanoparticles-dispersed carbon aerogels (Cu/CA). The samples were further activated sequentially under CO₂ and N₂ atmosphere. The final products under different activation temperature of secondary N₂ atmosphere were obtained and marked as Cu/CA-CO₂-N₂-T. The existence of highly dispersed Cu⁰ on the carbon aerogels was confirmed by XPS and HRTEM, which exhibited attractive activity towards electrochemical CO₂ reduction reaction (CO₂RR) forming carbon product in 0.1 M KHCO₃ aqueous media. Furthermore, the CO₂RR product distribution varied under different samples. The sample activated under 700 °C (Cu/CA-CO₂-N₂-700) with Cu loading c.a. 5.13 wt% showed remarkable CO faradaic efficiency (FE) (75.6%) at low overpotential of -0.49 V. Further calcination led to more exposure of copper, and CO dimerization to C2 product. The high selectivity toward CO by Cu/CA-CO₂-N₂-700 maybe attributed to their excellent stability in maintaining the metallic nature of Cu component within the hydrophobic carbon aerogels during electrocatalysis, which further prevents the adsorption and reduction of CO on the catalyst.

Keywords: CO(2) activation; CO(2) electrochemical reduction; Carbon aerogel; Cu nanoparticles; N(2) activation.