Inhibition of CO2 Carbonation Promotes Efficacy of Bicarbonate Electrolysis to CO

Abstract

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 FE_CO 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.