Efficient electrochemical reduction of CO2 into CO promoted by sulfur vacancies

Electrochemical conversion of carbon dioxide (CO2) into useful chemicals has attracted a lot of attention to store energy and reduce the greenhouse effect. Herein, a new electrocatalyst of carbon nanotubes coated with cadmium sulfide is reported, the faradaic efficiency (FE) of CO2 reduction reaction (CO2RR) to carbon monoxide (CO) is as high as 95%. We clearly demonstrate that sulfur vacancies (S-vacancies) are in-situ generated on the catalyst surface in CO2RR, which is evidenced by electron paramagnetic resonance spectra (EPR), in-situ differential electrochemical mass spectrometry (DEMS) and inductively-coupled plasma spectrometer (ICP). With the increase of S-vacancies, the catalytic activity of CO2RR to CO improve significantly and the charge-transfer resistance decrease. Combined with in-situ infrared absorption spectroscopy and density functional theory calculations, it can be concluded that the formation of S-vacancies changes the electron density of the catalyst surface and decreases the energy barrier for the conversion of COOH∗ to CO∗. Finally, we tried to power electrochemical reduction of CO2 with solar panel under natural light conditions, the energy conversion efficiency on CdS-CNT catalyst from solar energy to CO has been calculated, predicting a hopeful application prospect in the future.