Interfacial engineering of Pd/In₂O₃ regulates Pd⁰/oxygen vacancy balance for efficient CO₂ hydrogenation to formate

The catalytic performance of oxide-supported Pd catalysts in CO₂ hydrogenation is highly dependent on the interfacial cooperation between metallic Pd⁰ sites and defect-containing oxide domains. However, how to regulate this metal-oxide interfacial balance to simultaneously promote H₂ activation and CO₂-derived intermediate conversion remains insufficiently understood. Herein, we develop an interfacial engineering strategy to regulate the balance between metallic Pd⁰ sites and oxygen vacancies (Ov) in Pd/In₂O₃ catalysts through morphology-dependent metal-support interaction (MSI). Structural analyses reveal that hollow In₂O₃ nanotubes (h-In₂O₃) effectively moderate Pd-In₂O₃ interactions, preserve a higher fraction of metallic Pd⁰, and maintain accessible defect-associated oxide domains, thereby establishing a more favorable interfacial configuration than compact counterparts. Consequently, Pd/h-In₂O₃ delivers the highest formate production rate of 8178 ± 145 mmol_FA mol_Pd^-1 h^-1 at 60 °C and 2 MPa, representing a sixfold enhancement over rod-like Pd/In₂O₃ (Pd/r-In₂O₃), together with excellent stability. These findings highlight that the coordinated regulation of metallic-site preservation and defect accessibility is critical for constructing efficient metal-oxide interfaces for CO₂ hydrogenation to formate.