Black SnO₂–TiO₂ Nanocomposites with High Dispersion for Photocatalytic and Photovoltalic Applications

Highly dispersed black SnO2–TiO2 nanocomposites were successfully synthesized by the sol–gel method using a Sn–POBC–Ti single-source precursor (POBC = p-carboxybenzaldehydeoxime), which adjusted the nanocomposite structure at the molecular level. SnO2 and TiO2 in the composites were highly dispersed due to the linkage of a single-source precursor; no TiO2 crystalline phase showed up when Sn:Ti ≥ 1:1, and black SnO2–TiO2 nanocomposites can be achieved when Sn:Ti ≤ 1:1, which was probably caused by the transformation from Sn2+–Ti4+ to Sn4+–Ti3+. The black nanocomposite with Sn:Ti = 1:2 showed the best performance in methyl orange degradation, phenol degradation, as well as photovoltaic conversion in the photoanode form. This can be attributed to the high surface area and the nano-heterojunction of SnO2 −TiO2 caused by the highly dispersed elements of the single source precursor.