Enhancing CO2 Electroreduction to Methane with a Cobalt Phthalocyanine and Zinc-Nitrogen-Carbon Tandem Catalyst.

Developing copper-free catalysts for CO2 conversion into hydrocarbons and oxygenates is highly desirable for electrochemical CO2 reduction reaction (CO2 RR). Herein, we report a cobalt phthalocyanine (CoPc) and zinc-nitrogen-carbon (Zn-N-C) tandem catalyst for CO2 RR to CH4 . This tandem catalyst shows a more than 100 times enhancement of the CH4 /CO production rate ratio compared with CoPc or Zn-N-C alone. Density functional theory (DFT) calculations and electrochemical CO reduction reaction results suggest that CO2 is first reduced into CO over CoPc and then CO diffuses onto Zn-N-C for further conversion into CH4 over Zn-N4 site, decoupling complicated CO2 RR pathway on single active site into a two-step tandem reaction. Moreover, mechanistic analysis indicates that CoPc not only generates CO but also enhances the availability of *H over adjacent N sites in Zn-N4 , which is the key to achieve the high CH4 production rate and understand the intriguing electrocatalytic behavior which is distinctive to copper-based tandem catalysts.