Acidic Electroreduction of CO₂ to Multi-Carbon Products with CO₂ Recovery and Recycling from Carbonate

High Resolution Image Download MS PowerPoint Slide Gas-fed flow cells can facilitate high-rate electrochemical CO 2 reduction (CO 2 R). However, under alkaline and neutral conditions, CO 2 is lost through reaction with hydroxide ions to form (bi)carbonate. In acidic solutions, although (bi)carbonate is still formed due to increased pH at the electrode, the low bulk pH of the electrolyte solution can regenerate CO 2 which is then available for re-reaction or release─this therefore avoids permanent CO 2 loss. Here, we show how CO 2 is converted and released in a bipolar-membrane-based gas-fed flow cell for CO 2 R to multicarbon products (C 2+ faradaic efficiency >60%) employing an acidic catholyte. Under the highest conversion conditions, we showed that almost exclusively CO 2 R products were obtained at one outlet, while, at the second outlet, a nearly product-free stream of CO 2 was obtained due to the continuous internal regeneration from (bi)carbonate. The system presented here avoids permanent reactant loss through the straightforward recovery and recycling of CO 2 to improve the overall CO 2 utilization.