Degradation kinetics for photocatalytic reaction of methyl orange over Al-doped ZnO nanoparticles

• Al-doped ZnO (AZO) nanoparticles (1–8% Al) were prepared.
• The degradation kinetics of methyl orange on AZO photocatalysts was studied.
• The obtained kinetic parameters were used to examine the role of Al dopant in photocatalytic activity of AZO.
• The 3% of Al was found to be the optimum concentration in AZO.
• Suppression of recombination of photoinduced charge carriers is the most important factor in determining the photocatalytic degradation rate.

Al-doped ZnO nanoparticles with different Al concentrations were prepared and employed as photocatalysts for the degradation of methyl orange. The samples were characterized by XRD, FE-SEM, XPS, BET, UV–vis DRS and photoluminescence techniques. The kinetic behavior could be described in terms of the Langmuir–Hinshelwood model. The adsorption equilibrium constant increased with increasing Al concentration and the reaction rate constant showed a maximum at 3% Al. It can be deduced that the enhancement of photocatalytic activity of ZnO by addition of Al could be attributed not to increase of surface area but to effective suppression of photoinduced electrons and holes.

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