Electroreduction of CO2 to methane with triazole molecular catalysts

Abstract

The electrochemical CO₂ reduction reaction towards value-added fuel and feedstocks often relies on metal-based catalysts. Organic molecular catalysts, which are more acutely tunable than metal catalysts, are still unable to catalyse CO₂ to hydrocarbons under industrially relevant current densities for long-term operation, and the catalytic mechanism is still elusive. Here we report 3,5-diamino-1,2,4-triazole-based membrane electrode assemblies for CO₂-to-CH₄ conversion with Faradaic efficiency of (52 ± 4)% and turnover frequency of 23,060 h⁻¹ at 250 mA cm⁻². Our mechanistic studies suggest that the CO₂ reduction at the 3,5-diamino-1,2,4-triazole electrode proceeds through the intermediary *CO₂–*COOH–*C(OH)₂–*COH to produce CH₄ due to the spatially distributed active sites and the suitable energy level of the molecular orbitals. A pilot system operated under a total current of 10 A (current density = 123 mA cm⁻²) for 10 h is able to produce CH₄ at a rate of 23.0 mmol h⁻¹.