Interfacial electron redistribution in a TiO2/Mn3O4 hollow heterostructure for selective photocatalytic CO2-to-CO conversion.

Abstract

Selective photocatalytic CO₂-to-CO conversion remains challenging because of rapid charge recombination and insufficient CO₂ activation. Herein, a TiO₂/Mn₃O₄ hollow heterostructure was constructed through a SiO₂ hard-template strategy combined with in situ growth. The hollow hemispherical architecture provides an open and accessible structural platform for the in situ growth of Mn₃O₄ nanosheets and the construction of intimate TiO₂/Mn₃O₄ heterointerfaces. Uniformly anchored Mn₃O₄ nanosheets establish intimate heterointerfaces that induce interfacial electron redistribution and promote charge separation. As a result, TiO₂/Mn₃O₄ exhibits a CO evolution rate of 9.31 μmol g^-1 h^-1, which is 1.62 and 2.20 times higher than those of pristine TiO₂ and Mn₃O₄, respectively, together with a CO selectivity of 84.03%, an electron selectivity of 56.81%, and excellent cycling stability. X-ray photoelectron spectroscopy analysis reveals pronounced interfacial electronic redistribution between TiO₂ and Mn₃O₄, while photoelectrochemical measurements demonstrate enhanced charge separation and interfacial charge transfer. In situ diffuse reflectance infrared Fourier transform spectroscopy further confirms the preferential formation of *COOH and *CO intermediates, favoring the selective two-electron CO₂-to-CO conversion pathway. This work demonstrates that regulating interfacial electron redistribution through hollow heterostructure engineering is an effective strategy for achieving efficient and selective photocatalytic CO₂-to-CO conversion.