Inhibition of CO₂ Carbonation Promotes Efficacy of Bicarbonate Electrolysis to CO

The bicarbonate electrolysis process integrates CO2 regeneration with electrolysis, potentially lowering the energy consumption of CO2 conversion. Currently, efforts to elevate the partial current density of target products in bicarbonate electrolysis primarily focus on electrode design and optimization. However, a paradoxical issue is that the activated CO2 (a-CO2) derived from HCO3– tends to reconvert as the current density increases, due to the locally high pH environment. We found that more than 54% of a-CO2 was carbonated in bicarbonate electrolysis at 200 mA cm–2, which led to a reduction in the efficiency of CO2RR. Here, this issue was mitigated by simply introducing buffering additives into the bicarbonate solution. Specifically, with the addition of 20.0 mM ethylenediaminetetraacetic acid (EDTA), the FECO reached 75.3% at 200 mA cm–2, representing a 2.3-fold increase compared to the EDTA-free system. These findings suggest that enhancing buffering capacity is crucial for optimizing bicarbonate electrolysis.