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

Abstract

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.