Modulating d-band center of Co₃O₄ monolith by defects to boost CO₂ photoreduction: from charge transport limitation...

Developing efficient monolith catalysts for photocatalytic CO₂ reduction remains fundamentally challenging due to their inherently sluggish charge transfer. Herein, we report a Co₃O₄ catalyst with serious agglomeration and meanwhile rich in oxygen vacancies (V_O-r-Co₃O₄), which achieves an unexpected superior photocatalytic CO evolution rate of 19.56 mmol h^-1 g^-1. Experimental results and density functional theory (DFT) calculations reveal that V_O play a crucial role in optimizing the CO₂ reduction pathway. Specifically, the abundant V_O create a low-coordination environment around Co atoms, substantially weakening the CoO orbital hybridization. This directly induces a significant downshift of the Co 3d-band center, effectively alleviating the overbinding of reaction intermediates. Consequently, the energy barriers for both the rate-determining *COOH formation and CO desorption are substantially reduced. This work highlights the importance of local electronic modulation in overcoming the charge transport limitations of monolith catalysts, offering a cost-effective strategy to revitalize such materials for solar energy conversion.