Electrochemically Induced Surface Enrichment in Trace Bismuth‐Doped Antimony‐Based Catalysts for Highly Selective CO ₂ ‐to‐Formate Conversion

ABSTRACT

The development of low‐toxicity, cost‐effective Sb‐based catalysts for electrochemical CO ₂ reduction has attracted significant research interest. However, Sb‐based catalysts normally suffer from significant competitive hydrogen evolution reaction (HER). Herein, we synthesized trace Bi‐doped nanoporous Sb catalysts through dealloying of Mg‐Sb‐Bi precursors with different doping concentrations. Notably, electrochemically induced Bi surface enrichment occurred for these Bi‐doped Sb catalysts, which effectively enhances CO ₂ ‐to‐formate conversion by greatly suppressing HER as demonstrated by on‐line differential electrochemical mass spectrometry. Typically, the activated Sb catalyst with only 0.5 at.% Bi dopant exhibits a formate Faradaic efficiency of 86%, around 7 times that of the un‐doped Sb (13%). Multiple characterization techniques confirm the surface enrichment of Bi during the potential‐induced activation process. Especially, in situ attenuated total reflection surface‐enhanced infrared absorption spectroscopy, in situ Raman, and density functional theory calculations rationalize that the Bi surface enrichment could promote synergistic Sb‐Bi interactions that stabilize the OCHO* intermediate and selectively enhance formate production. This work provides fundamental insights into activating inert materials via trace elemental doping for efficient CO ₂ reduction.