New insights into the efficient charge transfer of ternary chalcogenides composites of TiO₂

A two-step solvothermal synthesis was adopted to prepare AgXSe₂-TiO₂ (X = In, Bi) composites. DFT study of the pristine parent samples showed the formation of the hexagonal phase of AgBiSe₂, and tetragonal phase of AgInSe₂ and TiO₂, which corroborated the experimentally synthesised structures. Both the AgBiSe₂-TiO₂ and AgInSe₂-TiO₂ composites displayed enhanced visible light absorption and reduced band gap in the UV-DRS patterns. The XPS results exhibited a shift in binding energy values and the TEM results showed the formation of spherical nanoparticles of both AgBiSe₂ and AgInSe₂. The PL signals displayed delayed recombination of the photogenerated excitons. The as synthesised materials were studied for their photocatalytic efficiency, by hydrogen generation, degradation of doxycycline, and antimicrobial disinfection (E. coli and S. aureus). The composite samples illustrated more than 95 % degradation results within 180 min and showed 5 log reductions of bacterial strains within 30 min of light irradiation. The hydrogen production outcomes were significantly improved as the AgBiSe₂ and AgInSe₂ based composites illustrated 180-fold and 250-fold enhanced output compared to their parent samples. The enhanced photocatalytic efficiency displayed is attributed to the delayed charge recombination of the photogenerated electron-hole pairs in the AgXSe₂-TiO₂ interface. Formation of a p-n nano heterojunction for AgBiSe₂-TiO₂ and type II heterojunction for AgInSe₂-TiO₂ composite are explained.