While most lab-scale CO2 reduction experiments are conducted at ambient temperatures (20-25°C), maintaining such low temperatures at an industrial scale will become challenging due to joule heating. In our study, we pushed the boundaries further than the already existing systems, opting for a higher temperature of 85°C for CO2 reduction. This deliberate choice was made to accentuate the deviations from ambient conditions and explore their effects on CO2 electrolyzers.Our current emphasis at elevated temperatures focuses on catalyst development, specifically addressing stability issues induced by the increased temperature. Nevertheless, it was soon discovered that several modifications were required to the system, both in terms of cell materials and operational conditions (e.g. gaskets, pressure arrangements, GDE type, etc.) to allow stable operation at 85°C for extended duration and especially to avoid flooding. Prior research provided valuable insights into the multifaceted impacts of elevated temperatures on the electrochemical reduction of CO2, and proof they go beyond catalyst kinetics. With this in mind, we have synthesized a series of bismuth-related nano catalysts, including oxidized, metallic and carbon containing nanoparticles, and have quantitatively evaluated their activity, selectivity towards formate, and stability at 85°C. Preliminary observations suggest that catalysts without carbon exhibit high initial selectivity, but demonstrate diminished stability over a 24-hour timeframe compared to catalysts with a protective carbon layer. Specifically, we observed an initially high faradaic efficiency toward formate of 85% for commercial bismuth oxide nanoparticles, in contrast to 75% for bismuth nanoparticles with carbon. However, over a 24-hour timeframe, the carbon-free catalyst showed a 20% decrease in FE, while for the carbon-containing catalyst this drop was halved in the same timeframe.By evaluating the role of carbon additives (e.g. their oxidation state, pore size, surface area, hydrophobicity, etc.) our results yield valuable insights into the impact of carbon additives on stability and overall performance, especially at elevated temperature. These findings uncovered critical aspects for catalyst design, providing essential knowledge for future larger-scale applications. Moreover, we shed light on the required advancements and remaining challenges for elevated temperature CO2 reduction electrolysis, which we believe will become the predominant mode of operation for CO2 electrolysis in the future. Figure 1
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