Lewis Acid Adsorption Promotes CO ₂ Enrichment for Efficient Formic Acid Electrosynthesis on Reconstructed Bi ₂ O ₂ CO ₃ in Acidic Media

In acidic media, electrocatalytic CO₂ reduction to formic acid (HCOOH) represents a promising strategy for producing value-added chemicals. However, a critical challenge persists in enhancing CO₂ adsorption and activation to suppress hydrogen evolution and boost product selectivity. Here, a Lewis acidic Zr-oxo cluster-rich porous confined structure decorated Bi₂O₂CO₃ catalyst (Bi₂O₂CO₃@PCN) is constructed via in situ electroreconstruction, which effectively promotes surface CO₂ enrichment and K⁺ confinement in acidic conditions. Spatially adjacent Zr-oxo clusters enhance CO₂ adsorption at the interface through Lewis acid-base interactions, facilitating the *OCHO intermediate formation. The optimized Bi₂O₂CO₃@PCN catalyst achieves a high HCOOH Faradaic efficiency (FE) of 95% across a broad potential window and demonstrates a 5.9-fold higher mass activity compared to Bi₂O₂CO₃ in acidic media at ‒1.8 V versus reversible hydrogen electrode. Notably, Bi₂O₂CO₃@PCN exhibits superior HCOOH FE compared to Bi₂O₂CO₃ under low-concentration CO₂ flow. Mechanistically, the strong binding of CO₂ molecules at Bi-O-Zr interfacial sites significantly lowers the hydrogenation barrier, while K⁺ enrichment repels protons and suppresses the hydrogen evolution reaction. This work underscores the pivotal role of surface confinement and Lewis acidic sites in regulating interfacial microenvironments and CO₂ adsorption, highlighting their potential for efficient conversion of low-concentration CO₂.