Electrochemical Reduction of CO2 on Au Electrocatalysts Under Commercially Relevant Condition

Abstract

Much effort has been devoted for development of effective catalysts for the electrochemical reduction of CO2 (CO2RR). For CO2RR, performing H-cell experiments is the most common catalyst screening method where the reactant CO2 gas is usually dissolved in an aqueous bicarbonate-based electrolyte1. However, the low solubility of CO2 in aqueous solutions (∼35 mM at 298 K and 1 atm pressure) causes mass transport limitations when using dissolved CO2 as the reactant. Based on H-cell measurements gold (Au) is one of the most selective catalysts for CO2RR to CO2. However, preparation of shape-controlled Au nanoparticles (NPs) based on conventional synthesis methods requires the use of surfactants and capping agents such as polyvinylpyyrolidone (PVP). Here, we report the electroreduction of CO2 on ligand-free Au NPs (Au-PVP-free NPs) and Au NPs with PVP (Au-PVP NPs) that were produced by laser ablation3. For this purpose, we used our recently introduced gas diffusion electrode (GDE) setup1 which supplies a continuous CO2 stream at the electrode−electrolyte interface to circumvent CO2 mass transport limitations of the conventional liquid cells4. Moreover, we performed same experiments in the H-cell setup to compare between these two screening methods. In both measurement setups, the presence of PVP favors hydrogen evolution reaction (HER). However, we also observed differences in performance of the same catalyst at same experimental conditions in these two setups, which highlights the importance of having commercially relevant conditions for catalyst screening.Finally, we investigated the influence of different binders and membranes on selectivity and activity of Au-PVP-free NPs that led to more robust electrodes performance for CO2RR. Figure 1