N-Heterocyclic Carbene Polymer-Stabilized Au Nanowires for Selective and Stable Reduction of CO2

Abstract

The structural stability of nanocatalysts during electrochemical CO₂ reduction (CO₂RR) is crucial for practical applications. However, highly active nanocatalysts often reconstruct under reductive conditions, requiring stabilization strategies to maintain activity. Here, we demonstrate that the N-heterocyclic carbene (NHC) polymer stabilizes Au nanowire (NW) catalysts for selective CO₂ reduction to CO over a broad potential range, enabling coupling with Cu NWs for one-step tandem conversion of CO₂ to C₂H₄. By combining the hydrophobicity of the polystyrene chain and the strong binding of NHC to Au, the polymer stabilizes Au NWs and promotes CO₂RR to CO with excellent selectivity (>90%) across -0.4 V to -1.0 V (vs RHE), a significantly broader range than unmodified Au NWs (-0.5 V to -0.7 V). Stable CO₂RR at negative potentials yields a high j_CO of 142 A/g _Au at -1.0 V. In situ ATR-IR analysis indicates that the NHC polymer regulates the water microenvironment and suppresses hydrogen evolution at high overpotential. Moreover, NHC-Au NWs maintain excellent stability during 10 h of CO₂RR testing, preserving the NW morphology and catalytic performance, while unmodified NWs degrade into nanoparticles with reduced activity and selectivity. NHC-Au NWs can be coupled with Cu NWs in a flow cell to catalyze CO₂RR to C₂H₄ with 58% efficiency and a partial current density of 70 mA/cm² (overall C₂ product efficiency of 65%). This study presents an adaptable strategy to enhance the catalyst microenvironment, ensure stability, and enable efficient tandem CO₂ conversion into value-added hydrocarbons.