Surface modifications of copper electrocatalysts: a strategy to increase selectivity and stability for electro-reduction of carbon dioxide

Abstract

The consumption of fossil fuels is the main cause of climate change, resulting in global warming due to the accumulation of greenhouse gases in the atmosphere, especially carbon dioxide (CO2). The conversion of CO2 into carbon-based fuels and raw materials allows the storage of energy ina renewable way and contributes to the reduction of greenhouse gas emissions. In this context, the electrochemical CO2 reduction reaction (ECO2RR) constitutes a very promising approach, especially if the electricity required for the catalytic ECO2RR comes from renewable sources. To date, copper (Cu) catalysts have demonstrated the greatest ability to produce hydrocarbons and alcohols, such as ethylene and ethanol, by ECO2RR. However, the development of systems that enables industrial scale conversion of CO2 into multicarbon products (C2+) using electrocatalysts that have selectivity, stability, and high Faradaic efficiency are still far from realization. In this regard, one of the strategies is coating of Cu electrodes with organic species. In general, the coating provides an increase in Faradaic efficiencies for C2+ products and a reduction in H2 generation and enhances the stability of the catalyst compared to the respective electrodes without the coating. These results are mainly associated with the stabilization of intermediates bound to the catalyst surface, the hydrophobicity of the coating layer, and the stabilization of surface Cu atoms due to coordination with the ligands present in the modifier molecule. In addition, the Cu electrode coating process allows for practical scaling up of the preparation of electrodes for ECO2RR. Therefore, the main objective of this project is to use polymers with groups having coordinating sites, and stable under ECO2RR conditions, such as polybenzimidazole (PBI), for coating Cu bulk electrodes and Cu nanostructures to use as electrocatalysts for ECO2RR. The Cu nanostructures will be formed from Cu coordination polymers of the [Cu(L)2]n type, using imidazole and benzimidazole as ligands (L). The electrochemical reduction of these coordination polymers willresult in the formation of Cu nanoclusters with controlled shape, size, and dispersion, which willbe stabilized by coating with PBI. With the coating of Cu bulk electrocatalysts and Cu nanostructures, it is intended to stabilize the Cu active sites of the catalysts during operating conditions, and, at the same time, modulate the selectivity and Faradaic efficiency for the formation of C2+ products. (AU)