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

Yanming Cai,Yuehe Lin,Yu-Chung Chang,Jiaju Fu,Jun-Jie Zhu,Wenlei Zhu,Yang Zhou,Qianhao Min

doi:10.1038/s41467-020-20769-x

Yanming Cai, Yuehe Lin + Show 6 more

Open Access

https://doi.org/10.1038/s41467-020-20769-x

Copy DOI

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.

Highlights

Single-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization
They are typically involved in homogeneous catalysis[20,21,22], which limits the catalytic performance by outer sphere electron transfer from the electrode in electrochemical catalysis[23,24]
The atomic absorption spectra verified that the Cu content in Cu-carbon dots (CDs) prepared at 250 °C was 0.44 wt%

Summary

Introduction

Single-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. Owing to the uniform coordination structures and unique electronic properties of metal centers, single-atom catalysts (SACs) have demonstrated excellent selectivity in various catalytic reactions[3,4,5,6,7]. Traditional atomic metal–nitrogencarbon moieties (M–N–Cs) are supported in micron-sized carbon-based substrates and form through the redispersion of aggregated metal nanoparticles under high temperature (above 800 °C)[10,11] This process is so extreme that it causes the N- and. They are typically involved in homogeneous catalysis[20,21,22], which limits the catalytic performance by outer sphere electron transfer from the electrode in electrochemical catalysis[23,24] To tackle this problem, researchers tried to immobilize metal phthalocyanines on carbon nanotubes to create heterogeneous catalytic surfaces[24,25,26]. Cu-CDs presented high CH4 Faradaic efficiency (78%) and turn over frequency (2370 h−1) at −1.44 and −1.64 V, respectively

Methods

Results

Conclusion