A decarbonized society is essential to maintain and further improve the standard of living for humankind. While the residential sector and short-distance transport have available solutions for electrification, several processes in the chemical industry (such as plastic manufacturing and base chemicals) still require carbon-based fuels as a resource [1].

One of the carbon-neutral technologies to produce base chemicals is electrochemical carbon dioxide reduction (CO₂R), powered by renewable electricity. CO₂R targets multiple base chemicals ranging from C₁- products like carbon monoxide (CO) to C₂+-products like ethylene (C₂H₄) [2].

CO₂R is already established at a lab scale. Implementation of gas-fed membrane electrode assembly (MEA) ‘zero-gap’ cells, as the state-of-the-art reactor design, demonstrates promising potential for a scale-up onto the commercial level [3,4]. However, the potential upscale MEA CO₂R electrolyzers are inevitably exposed to elevated temperatures, as a substantial part of the input energy dissipates as heat during the CO₂R process. Despite the higher temperatures once scaled up, limited research is available on the phenomena and bottlenecks present in CO₂R at industrial-relevant temperatures exposing a major knowledge gap in the field [5, 6].

This study presents the effects of industrial-relevant temperatures in MEA-based CO₂ electrolysis cells. In the first step, heat balance investigations are shown, proving that industry-size electrolyzers will require heat management and cooling. This acts as a basis for the main motivation why higher than ambient temperatures inevitably need to be investigated. We briefly demonstrate that a corridor of 40°C to 70°C is the most likely operatable range for low-temperature CO₂ electrolysis if industry-scale is achieved.

To investigate higher-than-ambient temperatures the usually present experimental setup has to be extended to provide temperature control for lab-scale MEA cells, the input gas, and the liquid electrolyte input. Thus, we will briefly introduce our experimental setup using a heating oven for the MEA cell and external heating of the anolyte reservoir. Additionally, the setup utilizes several devices to enhance the control over the humidity of the incoming gas-feed CO₂ to increase the control over the water balance of the system. We explicitly share our experimental setup to lower the entree bar to motivate other groups to expand their ambient temperature testing to industry-relevant temperatures.

Extensive flooding and salt formation are two of the main bottlenecks in the current state of the art for CO₂ electrolysis often occurring at the same time or briefly after each other [7-9]. To investigate the effect of higher temperatures on flooding and salt formation experiments in an AEM-based MEA cell, using Ag as the cathode-side catalyst partnered with an oxygen-evolving IrO₂ catalyst at the anode, are executed in a current density range of 100 mA/cm² to 400 mA/cm² in a temperature corridor from 25°C to 70°C degrees using KOH and KHCO₃ as anolytes. Our data shows that elevated temperature benefits the CO₂R runtime in MEA cells by diminishing the issue of salt formation, enabling operation at current densities of >200 mA/cm² even under high electrolyte concentration at temperatures of 50 °C and above. We link this to better solubility at higher temperatures combined with a smaller cation crossover rate. However, flooding remains an issue, especially at current densities higher than 300 mA/cm². Nevertheless,  higher temperatures also mitigate cell flooding time. The exact mechanisms transporting water from the anode to the cathode are currently debated. We suggest osmotic water drag as the main transport mechanism for water transport to the cathode side, backed up by our experimental temperature data with additional control experiments for the osmotic-pressure-relevant variables like anolyte concentration and cation type.