Synergy or Antagonism? Exploring the Interplay of SnO2 and an N‑OMC Carbon Capture Medium for the Electrochemical CO2 Reduction toward Formate

Abstract

Closing the anthropogenic carbon cycle by means of the sustainable electrochemical CO2 reduction (eCO(2)R) toward formate (FA) is a promising strategy for CO2 abatement, clearing the path toward a carbon neutral future. Currently, three possible reaction pathways have been identified for the eCO(2)R toward FA, all of which are initiated by the adsorption of CO2 on the electrocatalyst's surface. Therefore, a possible strategy to enhance the availability of CO2 near the active sites is to combine an active electrocatalyst material (here, SnO2) with a known carbon capture medium (here, nitrogen-doped ordered mesoporous carbon (N-OMC)). SnO2 was introduced in situ during the N-OMC synthesis, yielding SnO2-N-OMCs. We approached the state of the art for Sn-based N-doped carbon electrocatalysts in terms of performance under industrially relevant currents with an average FEFA of 59% for SnO2-N-OMC (6) and 61% for SnO2-N-OMC (2). Moreover, the SnO2-N-OMC electrocatalysts require a low overpotential, courtesy of the N-OMC support, compared to the state of the art, for the selective conversion of CO2 toward FA at the industrially relevant current density of 100 mA cm(-2). Additionally, the 24 h stability of the best performing SnO2-N-OMC electrocatalysts is explored, and pulverization/agglomeration and in situ SnO2 reduction are identified as major degradation pathways, allowing future research to be steered more accurately toward more stable Sn-based electrocatalysts for the eCO(2)R toward FA. An optimal combination of both the SnO2 species and the N-OMC carbon capture medium could result in a synergistic effect, especially when utilization of the N-OMC support material is optimized to morphologically stabilize the SnO2 active species.