Nitrided copper-iron composite oxides derived from layered double hydroxides for enhanced carbon dioxide electroreduction to methane and formic acid

Abstract

The reduction of carbon dioxide to valuable chemical products is a promising solution to address carbon balance and energy issues. Herein, amorphous nitrided copper-iron oxides are prepared by gas-phase nitriding of CuFe-layered double hydroxide precursors with urea as nitrogen source. Amorphous materials are more likely to generate defect vacancies during the reaction process, and these vacancies can function as active sites for catalytic reactions. Therefore, the obtained materials show high activity for CO2 electroreduction to methane and formic acid, achieving a total Faraday efficiency of 74.7% at −0.7 V vs RHE and exhibiting a continuous 10 h durability in the H-cell. The uniformly distributed Cu+ sites act as active sites by losing electrons to activate CO2. During the CO2 electroreduction, CO2 is converted to *COOH via proton-electron coupling, *COOH combines directly with a proton in solution to produce the HCOOH product, and the other part of *COOH undergoes a protonated dehydration process to form the *CHO intermediate which dehydrates again to form CH4. This study provides a new approach for designing CO2 electroreduction catalysts.