Synergistic Effect of the Electronic Structure and Defect Formation Enhances Photocatalytic Efficiency of Gallium Tin Oxide Nanocrystals

The design of photocatalysts with enhanced efficiency is pivotal to sustainable environmental remediation and renewable energy technologies. Simultaneous optimization of different factors affecting the performance of a photocatalyst, including the density of active surface sites, charge carrier separation, and valence and conduction band redox potentials, remains challenging. Here, we report the synthesis of ternary gallium tin oxide (GTO) nanocrystals (NCs) with variable composition and investigate the role of Ga3+ dopants in altering the electronic structure of rutile-type SnO2 NC lattice using steady-state and time-resolved photoluminescence spectroscopies. Substitutional incorporation of Ga3+ increases the band gap of SnO2 NCs, imparting the reducing power to the conduction band electrons, and causes the formation of acceptor states, which, in conjunction with electron trapping by donors (oxygen vacancies), leads to stabilization of the photoexcited carriers. Combination of a decrease in the charge recombination rate and adjustment of the conduction band reduction potential to more negative values synergistically promote the photocatalytic efficiency of the GTO NCs. The apparent rate constant for the photocatalytic degradation of rhodamine-590 dye by optimally prepared GTO NCs is 0.39 min–1, more than 2 times greater than that by benchmark AEROXIDE TiO2 P25 photocatalyst. The results of this work highlight the concept of using rational aliovalent doping of judiciously chosen metal oxide NC lattices to simultaneously manipulate multiple photocatalytic parameters, enabling the design of versatile and highly efficient photocatalysts