CO₂ Electroreduction to Near‐Unity CO Triggered by Built‐in Electric Field Over P‐N‐Heterojunction Cu₂O‐Cd(OH)₂ Interface

Abstract Cu‐based nanomaterials have attracted great attention as a new generation of CO₂ electroreduction catalysts. However, significant limitations in the selectivity for a single product impede their industrial applications. Herein, the built‐in electric field (BIEF) strategy for the design of Cu‐based nano‐catalysts is reported, achieving near‐unity CO synthesis via the electrocatalytic CO₂ reduction (ECR) on the synthesized P‐N‐heterojunction Cu₂O‐Cd(OH)₂ catalyst. This catalyst showcases extraordinary selectivity, attaining almost 100% CO Faraday efficiency (FE_CO), accompanied by exceptional stability. Furthermore, the industrial‐scale flow battery with Cu₂O‐Cd(OH)₂ as the cathode manifests FE_CO surpassing 99%, a CO partial current density (j_CO) as high as 303.21 mA cm⁻², and a durable cycling life. In situ characterization and density functional theory calculations revealed that the enhanced ECR activity stems from the Cu₂O‐Cd(OH)₂ catalyst interface, which accelerates the electron transfer from Cd(OH)₂ to Cu₂O, thus reducing the free energy barrier of CO₂‐to‐CO reaction intermediates and boosting the CO selectivity. This research offers insights into the construction of BIEF to fabricate efficient Cu‐based catalysts for ECR industrialization.