Enhancing ozone catalytic decomposition through acid treatment of α-MnO for improved activity and humidity resistance.

Post-etching method using dilute acid solutions is an effective technology to modulate the surface compositions of metal-oxide catalysts. Here the α-MnO catalyst treated with 0.1 mol/L nitric acid exhibits higher ozone decomposition activity at high relative humidity than the counterpart treated with acetic acid. Besides the increases in surface area and lattice dislocation, the improved activity can be due to relatively higher Mn valence on the surface and newly-formed Brønsted acid sites adjacent to oxygen vacancies. The remnant nitro species deposited on the catalyst by nitric acid treatment is ideal hydrophobic groups at ambient conditions. The decomposition route is also proposed based on the DRIFTS and DFT calculations: ozone is facile to adsorb on the oxygen vacancy, and the protonic H of Brønsted acid sites bonds to the terminal oxygen of ozone to accelerate its cleavage to O, reducing the reaction energy barrier of O desorption.