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

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 (CO2RR). 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 CO2RR according to the relationship between the energy barrier of *CO intermediate and molecular structures in the future.

Automated summary

Copper-based heterogeneous catalysts have low selectivity in CO2 hydrogenation, while molecular catalysts with well-defined active sites and tailorable structures can optimize performance. This study successfully immobilized EDTA molecules on carbon nanotube surfaces to convert CO2 to CH4, offering potential for controlling product selectivity in CO2 reduction processes in the future.