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

Abstract

Based on H-cell measurements, gold (Au) is one of the most selective catalysts for the CO 2 reduction reaction (CO 2 RR) 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 lasergenerated, surfactant-free Au NPs for the CO 2 RR 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 CO 2 stream at the electrodeelectrolyte interface to circumvent CO 2 mass transport limita-tions 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.

Surfactant-Free Colloidal Syntheses of Precious Metal Nanoparticles for Improved Catalysts

“…The ability to compare surfactant-free NPs and NPs prepared with a surfactant also recently showed the impact of PVP in tuning the selectivity of Au catalysts for the electrochemical CO 2 RR. The presence of PVP promoted the undesirable HER by inhibiting CO as a reduction product . This effect was more pronounced in a gas diffusion electrode (GDE) setup.…”

“…Here we concentrate on the latter. Metal loadings can strongly affect the properties of the catalysts. , As comparative studies typically are performed with a fixed amount of active metal, different metal-to-support ratios of the catalysts lead to different absolute amounts/volumes of supported catalyst. This can have substantial impacts in the utilization of the catalyst and the volume utilization in a reactor, possibly affecting mass transport phenomena (e.g., for the same mass of metal, a supported catalyst with high metal loading occupies a smaller volume).…”

Effective perspiration is essential to uphold the stability of zero-gap MEA-based cathodes used in CO2 electrolysers

“…In this study we show that the excess polymeric CA content, if not removed from the catalyst ink, blocks perspiration channels and acts as a promoter of flooding, thereby causing serious stability issues observed in zero-gap MEA cathode-based electrolysers used for CO 2 electroreduction. 30 In the paper we utilize a novel ICP-MS analysis-based approach to quantitatively monitor the amount of perspired electrolyte that exits the zero-gap MEA cathode and ends up in the water trap equipped to the gas outflow channel of the electrolyser (see Fig. 1b ).…”

Comparative Spectroscopic Study Revealing Why the CO2 Electroreduction Selectivity Switches from CO to HCOO– at Cu–Sn- and Cu–In-Based Catalysts

“…CO 2 can be electrochemically reduced into a variety of products including hydrocarbons, alcohols, carbon monoxide (CO), and formate (HCOO – ). Recent techno-economic analyses suggest that two-electron reduction of CO 2 into C 1 products (i.e., HCOO – and CO) presents the best route to economic feasibility in the near future. − CO and HCOO – are essential feedstocks used in various industrial applications ranging from chemical synthesis (Fischer–Tropsch) to energy conversion (e.g., fuel cells) through existing and emerging technologies. − The realization of electrochemical synthesis of these important molecules on a large scale will require catalysts with high activity and selectivity to the desired products, exceptional stability, sufficient earth abundance, and broad availability. New discoveries of improved catalysts, guided by a detailed understanding of structure–activity relationships, are needed in order to progress toward these targets.…”

“…Recent techno-economic analyses suggest that two-electron reduction of CO2 into C1 products (i.e., HCOOand CO) presents the best route to economic feasibility in the near future. [1][2][3][4] CO and HCOOare essential feedstock used in various industrial applications ranging from chemical synthesis (Fisher-Tropsch) to energy conversion (e.g., f uel cells) through existing and emerging technologies. [5][6][7][8][9] The realization of electrochemical synthesis of these important molecules at large scale will require catalysts with high activity and selectivity to the desired products, exceptional stability, sufficient Earth-abundance, and broad availability.…”