Construction of TiO-MnO 0D-2D nanostructured heterojunction for enhanced photocatalytic hydrogen production.

The low transfer efficiency and high recombination loss of photo-induced carriers in TiO2 are significant issues that hinder its photocatalytic activity. Herein, TiO2 nanoparticles (∼5 nm) were loaded on MnO2 nanosheets (40-60 nm) to form TiO2-MnO2 nanostructured heterojunction (0D-2D nanostructure unit), possessing a high specific surface area. The separation/transfer efficiency of photocarriers and the solar absorptivity of TiO2-MnO2 were improved, thus enhancing solar energy conversion efficiency. The enhanced transfer efficiency of carriers is associated with the 2D network of MnO2 and abundant oxygen vacancies serving as media for electron transport. The enhanced visible absorption and reduced recombination should be attributed to the narrowed bandgap and modified energy band structure. The photocurrent of TiO2-MnO2 increased obviously and the H2 production rate increased to 0.38 mmol g-1 h-1, compared with that of pure TiO2 (0.25 mmol g-1 h-1). The enhanced photocatalytic properties are also associated with the excellent water oxidation kinetics caused by MnO2 nanosheets.