Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

Abstract

Single-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

Single‐Atom Electrocatalysts for Multi‐Electron Reduction of CO2

“…Very recently, Cai et al. designed unique CuN 2 O 2 sites in a carbon‐dots‐based SAC, [ 75 ] in which the introduction of oxygen ligands can efficiently modify the electronic structures of center atoms for reducing the overall endothermic energy in CH 4 production. As a result, the catalyst presents high CH 4 Faradaic efficiency of 78% and turn over frequency of 2370 h −1 at −1.44 and −1.64 V (vs RHE) in aqueous electrolytes, respectively.…”

Research Progress and Application of Single-Atom Catalysts: A Review

“…The precious metal gold and silver single-atom catalysts have a high Faraday efficiency in the CO 2 reduction reaction, reaching more than 90%. Adjusting the coordination environment of single-atom catalysts and changing the electronic structure of the central atom can change the selectivity of the product and generate hydrocarbons other than CO [91]. The mono-atomic catalyst loaded on modified or doped carbon-based graphene shows superior electrochemical performance and can efficiently electrocatalyze CO 2 RR [92].…”

Copper single-atoms embedded in 2D graphitic carbon nitride for the CO2 reduction

“…In its fullypolymerized configuration, GCN presents structural cavities (six-fold N cavities) where SACs could be confined and stabilized through strong metal-nitrogen interactions 20,21 , although the formation of less regular polymorphs has to be carefully evaluated in order to investigate the correct coordination of the metal atoms. Compared with nitrogen-doped graphene-related materials, which are frequently used for the dispersion of SACs 7,[22][23][24][25][26] , GCN contains a higher amount and uniform type/arrangement of nitrogen species that offer abundant and more precisely defined coordination sites for single atoms [27][28][29] . No less important it is the fact that it has a relatively small band gap (2.7 eV; 30 ) therefore, it is able to absorb the light, reducing the external input necessary for the CO2RR 31 .…”