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

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 (FECO), accompanied by exceptional stability. Furthermore, the industrial‐scale flow battery with Cu2O‐Cd(OH)2 as the cathode manifests FECO surpassing 99%, a CO partial current density (jCO) 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.