Molecular Stabilization of Sub-Nanometer Cu Clusters for Selective CO2 Electromethanation

Electrochemical CO2 methanation powered by renewable electricity provides a promising approach to utilizing CO2 in the form of a high-energy-density, clean fuel. Cu nanoclusters have been predicted by theoretical calculations to improve methane selectivity. Direct electrochemical reduction of Cu-based metal-organic frameworks (MOFs) results in large-size Cu nanoparticles which favor multi-carbon products. This study concerns an electrochemical oxidation-reduction method to prepare Cu clusters from MOFs. The derived Cu clusters exhibit a faradaic efficiency of 51.2 % for CH4 with a partial current density of >150 mA cm(-2). High-resolution microscopy, in situ X-ray absorption spectroscopy, in situ Raman spectroscopy, and a range of ex situ spectroscopies indicate that the distinctive CH4 selectivity is due to the sub-nanometer size of the derived materials, as well as stabilization of the clusters by residual ligands of the pristine MOF. This work offers a new insight into steering product selectivity of Cu by an electrochemical processing method.

Automated summary

This study demonstrates the preparation of Cu clusters through an electrochemical method, showing excellent performance in methane selectivity. High-resolution microscopy and in situ spectroscopic analyses confirm the distinctive CH4 selectivity due to the sub-nanometer size of the clusters and the stabilization by residual ligands of MOF.