Electrochemical Reduction of CO2 on Au Electrocatalysts in a Zero-Gap, Half-Cell Gas Diffusion Electrode Setup: a Systematic Performance Evaluation and Comparison to a H-cell Setup

Based on H-cell measurements, gold (Au) is one of the most selective catalysts for the CO2 reduction reaction (CO2RR) to CO. To ensure a high dispersion, typically Au small nanoparticles (NPs) are used as catalyst. However, the preparation of small Au NPs based on conventional synthesis methods often requires the use of surfactants such as polyvinylpyrrolidone (PVP). Here, we present a systematic evaluation of the performance of laser-generated, surfactant-free Au NPs for the CO2RR in a gas diffusion electrode (GDE) setup and compare the results to investigations in an H-cell configuration. The GDE setup supplies a continuous CO2 stream at the electrode−electrolyte interface to circumvent CO2 mass transport limitations encountered in conventional H-cells. We investigate the influence of the catalyst loading and the effect of PVP. Comparing the two screening methods, i.e. GDE and H-cell measurements, it is shown that the performance of the same catalyst can be substantially different in the two environments. In the GDE setup without liquid electrolyte-catalyst interface a higher reaction rate, but lower faradaic efficiendy is determined. Independent of the setup, the presence of PVP favours the hydrogen evolution reaction (HER), however, in the GDE setup PVP is more detrimental for the performance than in the H-cell.