General Synthetic Strategy to Ordered Mesoporous Carbon Catalysts with Single-Atom Metal Sites for Electrochemical CO2 Reduction.

ABSTRACT

The electrochemical carbon dioxide reduction reaction (CO2 RR) is a transformative technology to reduce the carbon footprint of modern society. Single-site catalysts have been demonstrated as promising catalysts for CO2 RR, but general synthetic methods for catalysts with high surface area and tunable single-site metal composition still need to be developed to unambiguously investigate the structure-activity relationship crossing various metal sites. Here, a generalized coordination-condensation strategy is reported to prepare single-atom metal sites on ordered mesoporous carbon (OMC) with high surface areas (average 800 m2  g-1 ). This method is applicable to a broad range of metal sites (Fe, Co, Ni, Cu, Pt, Pd, Ru, and Rh) with loadings up to 4 wt.%. In particular, the CO2 RR to carbon monoxide (CO) Faradaic efficiency (FE) with Ni single-site OMC catalyst reaches 95%. This high FE is maintained even under large current density (>140 mA cm-2 ) and in a long-term study (14 h), which suits the urgently needed large-scale applications. Theoretical calculations suggest that the enhanced activity on single-atom Ni sites results from balanced binding energies between key intermediates, COOH and CO, for CO2 RR, as mediated by the coordination sphere.