Design of a Rotating Disk Electrode setup operating under high pressure and temperature: Application to CO2 reduction on gold

We describe the design and development of a rotating disk electrode (RDE) cell capable of operating at pressures up to 200 bar and temperatures up to 200 °C. This setup enables electrochemical surface characterization through techniques such as voltammetry and impedance spectroscopy, under different mass transport regimes. Furthermore, evaluation of catalytic performance, including CO2 reduction, is possible as the system works in a semi-continuous mode interfaced with online gas sample measurements. As a proof of concept of the high-pressure cell designed, we examined the temperature-dependent changes in the cyclic voltammograms (CVs) of polycrystalline gold up to 150 °C and 50 bar. Additionally, online catalytic performance of CO2 reduction to CO on a rotating polycrystalline gold disk electrode was investigated under different pressure and temperature. Our results indicate a positive impact of temperature on the faradaic efficiency (FE) towards CO up to 50 °C, beyond which a rapid drop in performance was observed at atmospheric pressure. Conversely, increasing pressure positively affected CO2 solubility in the electrolyte, resulting in enhanced FE towards CO, reaching approximately 90 % at 6 bar compared to 40 % at atmospheric pressure. Notably, further increases in pressure did not significantly alter the FE, but led to higher current densities. Moreover, at pressures exceeding 6 bar, we observed a plateau in efficiency at temperatures higher than 50 °C. This observation suggests that increasing pressure can sustain CO2 electrolysis, validating the hypothesis that increasing CO2 solubility would suppress catalytic decay at higher temperatures. This study opens up promising avenues for future investigations in electrocatalysis, ranging from fundamental explorations of surface modifications induced by variations in temperature and pressure to the development of high-performance catalysts. [Display omitted]