Plasmonic Ag-Integrated Mesoporous Mn ₂ O ₃ –TiO ₂ Thin Films for Efficient Solar Hydrogen Production

The present work describes the synthesis of mesoporous Mn2O3–TiO2 (TiMn) and Ag-integrated TiMn (TiMnAg) nanocomposites, and their superior photocatalytic activity in a thin-film form was demonstrated for solar H2 generation in direct sunlight. The integration of metallic Ag and TiMn significantly enhanced solar H2 production due to the combined effect of Schottky junction and heterojunction formation. The PIRET (plasmon-induced resonance energy transfer) effect of Ag and the consequent energy transfer to the surrounding lattice, and heterogeneous distribution of metal ions on the TiO2 surface with possible synergistic interactions among them, are additional reasons for efficient solar-to-chemical energy conversion. TiMnAg-1 (0.5 wt % Ag-loaded on TiMn) and TiMn-3 (TiO2:Mn = 1:0.03 mol ratio) showed the highest H2 production rate (9.05 mmolh–1g–1), which is 60 times higher than that of bare TiO2 (0.16 mmolh–1g–1). TiMnAg-1 fabricated in a thin-film form shows 5.2 times higher solar H2 production activity than its powder counterpart. The interconnected mesoporous network in TiMnAg-1 is an additional advantage, which enhances diffusion and mass transfer during the reaction. The plausible photocatalytic reaction mechanism of the TiMnAg nanocomposites involves direct energy and electron transfer from metallic Ag nanoparticles and Mn2O3 species, respectively, to TiO2, which is then utilized for the reduction of H+ to H2.