Electrochemical Reduction of CO 2 on Au Electrocatalysts in a Zero‐Gap, Half‐Cell Gas Diffusion Electrode Setup: a Systematic Performance Evaluation and Comparison to an 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 small Au nanoparticles (NPs) are used as a catalyst. However, the preparation of small Au NPs based on conventional synthesis methods often requires the use of surfactants such as polyvinylpyrrolidone (PVP). Here, a systematic evaluation of the performance of laser-generated, surfactant-free Au NPs for the CO2RR in a gas diffusion electrode (GDE) setup was presented and the results were compared to investigations in an H-cell configuration. The GDE setup supplied a continuous CO2 stream at the electrode-electrolyte interface to circumvent CO2 mass transport limitations encountered in conventional H-cells. The influence of the catalyst loading and the effect of PVP were investigated. By comparing the two screening methods, that is GDE and H-cell measurements, it was shown that the performance of the same catalyst could be substantially different in the two environments. In the GDE setup without liquid electrolyte-catalyst interface a higher reaction rate, but lower faradaic efficiency was determined. Independent of the setup, the presence of PVP favoured the hydrogen evolution reaction (HER). However, in the GDE setup PVP was more detrimental for the performance than in the H-cell.