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

• Al-doped SrTiO 3 boosts visible light photocatalytic efficiency (87% MB removal). • Rh/Cr 2 O 3 and CoOOH co-catalysts enhance charge separation in Al-doped SrTiO 3 . • Composite achieves 100% MB degradation in 45 min, showing superior performance. 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. The photocatalyst was prepared by first synthesising SrTiO 3 nanoparticles by chemical precipitation followed by calcination. Then, SrTiO 3 was doped with aluminium using a flux method with Al 2 O 3 and SrCl 2 at 1150 °C. Finally, the dual co-catalysts, Rh/Cr 2 O 3 and CoOOH, were photodeposited onto SrTiO 3 @Al via sequential irradiation. The Rh/Cr 2 O 3 /SrTiO 3 @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.