Hierarchical Tandem Catalysis Promotes CO Spillover and Trapping for Efficient CO₂ Reduction to C₂₊ Products

Abstract

The electrochemical CO₂ reduction reaction (CO₂RR) to produce multicarbon (C₂₊) hydrocarbons or oxygenate compounds is a promising route to obtain a renewable fuel or valuable chemicals; however, producing C₂₊ at high current densities is still a challenge. Herein, we design a hierarchically structured tandem catalysis electrode for greatly improved catalytic activity and selectivity for C₂₊ products. The tandem catalysis electrode is constructed of a sputtered Ag nanoparticle layer on a hydrophobic polytetrafluoroethylene (PTFE) membrane and a layer of nitrogen-doped carbon (NC)-modified Cu nanowire arrays. The Cu nanowire arrays are <i>in situ</i> grown on PTFE by electrochemical oxidation of sputtered CuAl alloy, in which the chemical etching of metal Al induces the formation of a Cu nanowire array structure. Within hierarchical configuration, CO can be efficiently generated on an active Ag layer and then spillover and transfer to NC-modified Cu nanowire array layer, in which Cu/NC interfaces can enhance *CO trapping and adsorption. During the CO₂RR, the optimized tandem catalysis electrode achieves superior Faradaic efficiencies of 53.5% and 87.5% for ethylene (C₂H₄) and C₂₊ products at the current density of 519.0 mA cm^-2, respectively, with a high C₂₊/C₁ ratio of 10.42 and long-term stability up to 50 h. <i>In situ</i> Raman and attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) confirm that the Ag-Cu-NC tandem catalysis system significantly enhances the linear adsorption of *CO intermediates and the dissociation of H₂O, improves the C-C coupling capability, and stabilizes the key intermediate *OCCOH to produce C₂₊ products.