Hierarchical nanostructures self-assembled from δ-MnO2 ultrathin nanosheets and Mn3O4 octahedrons for efficient room-temperature HCHO oxidation

Abstract

Given the prevalence and severity of indoor HCHO pollution, the efficient elimination of HCHO is of great urgency. Hierarchical Pt/δ-MnO₂/Mn₃O₄ constructed from ultrathin δ-MnO₂ nanosheets and octahedron-shaped Mn₃O₄ nanoparticles was synthesized. About 1.19 mg of HCHO was oxidized over 0.1 g of Pt/δ-MnO₂/Mn₃O₄ (0.5 wt% Pt) within 1 h at room temperature. Pt/δ-MnO₂/Mn₃O₄ (0.1 wt% Pt) exhibited higher activity (0.91 mg) than Pt/commercial-MnO₂ (0.5 wt% Pt, 0.87 mg). The enhanced performance of Pt/δ-MnO₂/Mn₃O₄ mainly arose from three factors. Hierarchical texture consisting of ultrathin nanosheets and octahedral nanoparticles endowed the catalysts with high mass transfer efficiency and good Pt-dispersion through providing numerous accessible meso-/macropores and abundant available Pt-deposition sites. Ultrathin δ-MnO₂ nanosheets with a high proportion of surface atoms offered a large number of active centres and highly mobile lattice oxygen for HCHO adsorption and oxidation. Active surface oxygen could be generated via a dual-pathway including emergence on the surface of Pt atoms and development through Mn⁴⁺/Mn³⁺ cycles, giving rise to a superb catalytic activity. This work provided a feasible approach for synthesizing low-cost catalysts with excellent performance toward HCHO removal at room temperature.