Role of Ethylene Diamine Tetraacetate as an Additive in Electrolyte on Intermediate Stabilization in Electrochemical CO₂ Reduction

Although an electrochemical CO₂ reduction reaction (ECO₂RR) can provide an ideal route to produce CH₄, its selectivity is significantly hindered due to kinetically complex steps. To improve CH₄ selectivity, this study focuses on microenvironmental engineering using an additive of ethylene diamine tetraacetate (EDTA) in electrolyte. EDTA interacts with the Cu catalyst, altering its electronic structure and promoting CO₂ activation, in addition, it forms additional hydrogen bonding with key intermediates of *CO and *CHO leading to their stabilization. These phenomena were experimentally and theoretically demonstrated as exhibiting the facilitated CO₂ adsorption and the *CO to *CHO conversion with suppressing *CO desorption. As a result, Cu-loaded N-doped Carbon (Cu/N : C) with EDTA additive in electrolyte shows a significantly enhanced CH₄ selectivity, reaching a faradaic efficiency (FE) of 48 % and a partial current density (J_CH4) of 15.0 mA cm^-2 at -1.8 V_RHE. This performance surpasses that of pristine Cu/N : C, which exhibited marginal FE and J_CH4 values of 32 %, and 6.8 mA cm^-2, respectively. It obviously emphasizes the importance of intermediate stabilization via microenvironmental engineering for selective CH₄ production. This approach provides great insight into developing an effective ECO₂RR system for promoting CO₂ to value-added chemicals and fuel conversion.