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. Electrochemical CO2 reduction to make fuels and feedstocks often relies on metal-based catalysts. Here the authors report membrane electrode assemblies operating with relatively high current densities for CO2-to-CH4 conversion using organic molecular catalysts.