Bimetallic Tandem Strategy for Effective Modulation of CO ₂ Electrocatalytic Selectivity on Relatively Inert Cu Interfaces

The development of effective strategies to enhance the activity and selectivity of Cu-based catalysts for the CO₂ reduction reaction (CO₂RR) remains a critical challenge, particularly on relatively inert Cu facets that are highly active in the competitive hydrogen evolution reaction (HER). In this study, a series of Cu-M (M = Au, Ag, Pd) bimetallic tandem interfaces are fabricated on Cu nanocolumn arrays (Cu NCAs) with predominantly exposed Cu (200) facets. These interfaces excited a significant number of Cu⁺ species and modulated the adsorption behavior of critical intermediates for CO₂RR, resulting in improved CO₂RR activity and a substantial reduction in the competitive HER. Notably, the Cu-Au, Cu-Ag, and Cu-Pd NCAs displayed excellent selectivity for C₂H₄, CO, and HCOOH products, with optimized faradaic efficiency (FE) of ≈43.2, ≈48.0, and ≈50.7%, respectively. According to in situ spectroscopic analysis, each Cu-M interface exhibited distinct catalytic pathways: Cu-Au favored *COOH and *CO adsorption followed by C-C coupling for C₂H₄ production, Cu-Ag promoted *CO desorption for CO generation, and Cu-Pd facilitated *OCHO formation for HCOOH production. This study provides a strategy to design high-performance and more practical bimetallic Cu-based catalytic electrodes by directly modifying various commercial Cu substrates.