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

Abstract

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 (JCH4) of 15.0 mA cm−2 at −1.8 VRHE. This performance surpasses that of pristine Cu/N : C, which exhibited marginal FE and JCH4 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.