Excess Al Reduces Photocatalytic Activity of Al-Doped SrTiO ₃ Nanostructures

Chemical pollution poses a major threat to environmental and human health, necessitating efficient remediation strategies. Photocatalysis offers a promising approach, yet its effectiveness is often limited by charge recombination and surface reactivity. Here, we investigate aliovalent doping of strontium titanate (SrTiO 3 ) with aluminum to enhance photocatalytic degradation of organic pollutants, including the anionic dye methyl orange and the chlorinated pesticide 2,4-dichlorophenoxyacetic acid (2,4-D). SrTiO 3 nanoparticles were synthesized via solid-state reaction and subjected to flux-mediated Al doping (0–20 mol %). High-resolution electron microscopy revealed a previously unreported Al-enriched surface layer at high doping levels (>5 mol %), which correlates with reduced photocatalytic activity. The highest degradation rate was observed for nominally undoped samples (0 mol % Al, sourced from the crucible), suggesting surface Al accumulation inhibits charge migration and pollutant adsorption. Scavenger experiments identified superoxide anions as key reactive species. Furthermore, C–Cl bond cleavage in 2,4-D confirms the material’s potential for remediating persistent organic pollutants. These findings provide mechanistic insight into dopant distribution and surface effects, guiding future design of photocatalysts for environmental applications.