Efficient photocatalytic degradation of methylene blue via synergistic dual co-catalyst on SrTiO3@Al under visible light: Experimental and DFT study

Abstract

Background

Photocatalytic oxidation is a green method for water purification. However, the operation of traditional photocatalysts depends on exposure to UV radiation, which only forms a small portion of the spectrum comprising sunlight. The expansion of photocatalyst absorption to the visible range of light could greatly improve the efficiency and economic viability of the process.

Methods

The photocatalyst was prepared by first synthesising SrTiO₃ nanoparticles by chemical precipitation followed by calcination. Then, SrTiO₃ was doped with aluminium using a flux method with Al₂O₃ and SrCl₂ at 1150 °C. Finally, the dual co-catalysts, Rh/Cr₂O₃ and CoOOH, were photodeposited onto SrTiO₃@Al via sequential irradiation.

Significant findings

The Rh/Cr₂O₃/SrTiO₃@Al/CoOOH nanocomposite degraded 87% of methylene blue (MB) (10 mg/L) under visible light in 1 h, a 3.3-fold improvement over pure SrTiO3 and 2.1-fold over a similar commercial composite. This enhancement is due to efficient charge separation resulting from Al doping and improved carrier transport as a result of the anisotropic deposition of the co-catalysts. Optimisation showed that 20 mg of photocatalyst in 50 mL of MB solution (5 mg/L) degraded 100% thereof within 45 min. DFT calculations showed uneven electron distribution in SrTiO3′s conduction band and structural changes with Al doping, further enhancing photocatalytic activity.