MOF Encapsulating N-Heterocyclic Carbene-Ligated Copper Single-Atom Site Catalyst towards Efficient Methane Electrosynthesis.

The exploitation of highly efficient carbon dioxide reduction (CO2RR) electrocatalyst for methane (CH4) electrosynthesis has attracted great attention for the intermittent renewable electricity storage, but remain challenges. Here, N-heterocyclic carbene (NHC)-ligated Copper single atom site (Cu SAS) embedded in metal organic framework is reported (2Bn-Cu@UiO-67), which can achieve an outstanding Faradaic efficiency (FE) of 81% for the CO2 reduction to CH4 at -1.5 V vs RHE with a current density of 420 mA cm-2. Notably, the CH4 FE of our catalyst remains above 70% within a wide potential range, and achieves an unprecedented turnover frequency (TOF) of 16.3 s-1, which almost represents the best molecular catalyst for CH4 electrosynthesis to date. The experimental results show that the σ donation of NHC enriches the surface electron density of Cu SAS and promotes the preferential adsorption of CHO* intermediates. Meanwhile, the porosity of the catalyst facilitates the diffusion of CO2 to 2Bn-Cu, thereby significantly increasing the availability of each catalytic center. This NHC-ligated Cu SAS catalyst design has great advantages in CH4 electrosynthesis and provides ideas for the commercial production of CH4.