Enhanced visible light photocatalytic performance of SnO₂ nanoparticle co-doped with (Co, Nb) for organic dye degradation

Fast electron–hole recombination rate, lower free radical generation, unsuitable valence band maximum (VBM) and conduction band minimum (CBM) position of SnO₂ nanoparticle are the shortfalls in achieving a superior photocatalytic performance of organic dye degradation under sunlight irradiation. To rise above these margins, for the first time, the co-doping approach was attempted by a simple co-precipitation technique in which both cobalt (Co) and niobium (Nb) were doped in SnO₂ nanoparticle. In this regard, pure, mono-doped 5 M Co, 5 M Nb and different concentrations of (Co, Nb) co-doped SnO₂ nanoparticles were prepared and characterized through XRD, UV–Vis, PL, XPS, SEM, and cyclic voltammetry analyses. Moreover, the influence of crystalline nature, bond order, bandgap, electron–hole recombination rate, and VBM and CBM potential to the efficient photocatalytic activity have been discussed. The observed UV–Vis, PL, and cyclic voltammetry measurements revealed that the (Co, Nb) co-doped SnO₂ nanoparticles have suitable CBM to meet better reduction capacity, lower electron–hole recombination rates, and higher stability than pure and mono-doped system. XPS analysis confirmed the presence of both Co and Nb in the SnO₂ matrix and O1s spectrum revealed the presence of hydroxyl radical on its surface. Also, the terephthalic (TA) acid test showed that, at higher concentration of cobalt co-doped SnO₂ nanoparticles, it generated maximum hydroxyl (OH^·) radicals than that of others. Consequently, those nanoparticles exhibited 99% efficiency of methylene blue (MB) dye degradation at 30 min under direct sunlight atmosphere. For better photocatalytic outsight, the photodegradation mechanism was also proposed.