Valence state heterojunction Mn3O4/MnCO3: Photo and thermal synergistic catalyst

• Valence state heterojunctions Mn3O4/MnCO3 are synthesized.
• Mn3O4/MnCO3 heterojunctions exhibit photo and thermal catalysis effect.
• A possible mechanism of photo and thermal synergistic catalysis is illustrated.

The valence state Mn3O4/MnCO3 heterojunctions were synthesized using a facile, wet chemical oxidation method during hydrothermal process. Their crystal structures, morphologies and optical properties were systematically investigated. The obtained Mn3O4/MnCO3 exhibited photo and thermal synergistic catalysis which have been estimated via degradation of methylene blue (MB) and HCHO under visible light (λ > 420 nm) irradiation at different temperature (20 °C, 60 °C and 80 °C). Mn3O4 and MnCO3 possessed matching band potentials that could prevent the recombination rate of photogenerated electrons and holes in the reaction, which proved by the PL intensity of the samples, resulting in a great enhancement on their catalytic efficiency. Catalytic activity of Mn3O4/MnCO3 under photo and thermal effect was not the simple summation of photocatalysis and thermocatalysis, but a synergistic effect was existed in Mn3O4/MnCO3 composites which possessed much lattice oxygen to capture the holes leading to efficiently oxidizing reaction at high temperature. A possible mechanism was proposed based on valence state heterojunction to illustrate the synergistic effect between photo and thermal catalysis on degradation of organic pollutions.

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