Lewis-Basic EDTA as a Highly Active Molecular Electrocatalyst for CO2 Reduction to CH4.

Abstract

The most active catalysts so far successful in hydrogenation reduction of CO2 are mainly heterogeneous Cu-based catalysts. The complex coordination environments and multiple active sites in heterogeneous catalysts result in low selectivity of target product, while molecular catalysts with well-defined active sites and tailorable structures allow mechanism-based performance optimization. Herein, we firstly report a single ethylenediaminetetraacetic acid (EDTA) molecular-level immobilized on the surface of carbon nanotube as a catalyst for transferring CO2 to CH4 with an excellent performance. This catalyst exhibits a high Faradaic efficiency of 61.6 % toward CH4 , a partial current density of -16.5 mA cm-2 at a potential of -1.3 V versus reversible hydrogen electrode. Density functional theory calculations reveal that the Lewis basic COO- groups in EDTA molecule are the active sites for CO2 reduction reaction (CO2 RR). The energy barrier for the generation of CO from *CO intermediate is as high as 0.52 eV, while the further protonation of *CO to *CHO follows an energetic downhill path (-1.57 eV), resulting in the high selectivity of CH4 . This work makes it possible to control the product selectivity for CO2 RR according to the relationship between the energy barrier of *CO intermediate and molecular structures in the future.