Nanostructure engineering of Cu electrocatalyst for the selective C2+hydrocarbons in electrochemical CO2 reduction

Abstract

In recent years, the selective conversion of CO2 to fuels and chemicals has been deliberated as one of the key challenges in the electrochemical CO2 reduction reaction (CO2 RR). The copper (Cu)-based materials were demonstrated to achieve the selective products from the electrochemical CO2 RR and received significant attention due to the special morphological features, which enhance the mass transport and electrical conductivity. In present work, we modulated the morphology of Cu electrocatalysts by developing the Cu-aluminum (Al) (Cu80Al20) alloy on carbon paper through co-deposition of Cu and Al elements with a different ratio by a thermal evaporation method. Followed by etching the Al content by immersing in alkaline NaOH solution resulting the formation of nanostructured Cu-Al layer. Herein, the Cu layer showed the nanowire structure with the cupric oxide (Cu2O) phase. An interesting finding was that the faradic efficiency of the final products could be tuned by dealloying process where the composition of the Cu and Al elements has been changed. Thus, the electrocatalytic activity and selectivity of CO2 conversion into C2+ of the modified structure-dependent catalysts have been investigated. Herein, the as-deposited Cu, co-deposited Cu80Al20, and etched Cu80Al20 layers were adapted to evaluate the fundamental electrochemical properties for electrochemical CO2 RR using flow electrolyzer based on gas-diffusion electrodes in the 1 M KHCO3 electrolyte. The etched Cu80Al20 catalysts exhibited the highest C2+ faradaic efficiency (FEC2+) of 72.1% at-0.84 V-RHE, higher than of the as-deposited Cu catalyst (11.7%) and co-deposited Cu80Al20 catalyst (46.0%), respectively. It can be attributed to the more active electrochemical surface area, low overpotential, and charge transfer resistance. Morever, the possible additional favorable adsorption states of intermediates (*CO-COH) on the surface of the etched Cu80Al20 catalysts layer.