Activation or passivation: Influence of halogen dopant (F, Cl, Br) on photothermal activity of Mn2O3 in degrading toluene

Mn 2 O 3 is an exceptional earth-abundant mineral that has been extensively applied in catalytic oxidation because of the strong redox couples like Mn 3+ /Mn 2+ and Mn 4+ /Mn 3+ exposed on Mn 2 O 3 surface. Herein, the catalytic activity of Mn 2 O 3 in photothermal degradation of toluene was regulated by halogens including F - , Cl -, and Br - . As the electronegativity ordered in F (3.98) > O (3.44) > Cl (3.16) > Br (2.96), F - doped Mn 2 O 3 overperforms Cl - doped and Br - doped Mn 2 O 3 in decomposing toluene. DFT theoretical calculation illustrates that F - attracts the shared electrons from Mn to itself, the deviated charge center stretches the adjacent Mn-O bonds and boosts the generation of abundant oxygen vacancies, helping to strengthen the catalytic activity of Mn 2 O 3 . Conversely, Mn-O bonds are shortened by Cl - and Br - that have lower electronegativity than O. The multiple electrons circling Cl - and Br - push Mn towards O and squeeze Mn-O bonds, resulting in the formation of passivated Mn 2 O 3 . In conjunction with Mn redox couples and oxygen vacancies, 99% of 400 ppm toluene can be eliminated by F - doped Mn 2 O 3 , corresponding mineralization rate is high up to 95.8%.