(Invited) Development of Energy-Efficient and Scalable Electrochemical Devices for CO₂ to Formate Conversion

CO 2 electrochemical reduction to useful chemicals has drawn significant interest over the past decade, as the technology shows promising potential for coupling with renewable energies and helping reduce the overall CO 2 emission. 1 Among different CO 2 reduction (CO2R) end products, formate has some economic advantages because it is easier for downstream separation as a liquid product, and has many applications, such as hydrogen storage 2 and biomass conversion 3 . Several studies have shown that using SnO 2 or Bi-based catalyst, the Faradaic efficiency (FE) for CO 2 to formic acid/formate can be high (>80%). 4,5 However, many literature-reported CO 2 to formic acid/formate systems either has very high cell voltage during operation or contain complex chamber structures that induces large Ohmic drops or make it very hard for scaling up. In this study, we explored different pathways for CO 2 to formate electrochemical conversion that are both energy-efficient and scalable. Several cell configurations were investigated regarding cell voltage, energy consumption, and FE. As shown in Figure 1a, by optimizing the cell configuration, we can get the cell voltage 50% lower compared to the previous reported bipolar membrane with catholyte chamber configuration. The FE is 80.1% at 400 mA/cm 2 and 79.5% at 500 mA/cm 2 . The overall energy consumption of the formate production is < 0.2 kWh/mol. We will talk about the advantage of different cell configurations we explored and the stability of each of those systems. Figure 1