Promoting Pd/Al2O3 catalysts for toluene combustion by DBD plasma treating in different working gas atmospheres

To investigate the effects of plasma treatment on supported precious metals for VOCs combustion, a series of 1% Pd/Al2O3 catalysts were synthesized by DBD plasma treating in different working gases (H2/Ar, O2, N2, Air) and with reversed calcination sequences. It is revealed that both the working gas and treating sequence can alter the Pd dispersion degree, valence states and the concentration of surface acid sites, which subsequently impacts the catalytic activity. Usually, a Pd/Al2O3 catalyst with a higher active Pd surface area shows higher toluene combustion activity, due to the promoted ability to adsorb and activate toluene molecules. Therefore, Pd dispersion degree is the main factor to determine the reactivity of Pd/Al2O3 catalysts. Moreover, H2/Ar plasma treating can effectively create Pd0 sites, which is favorable to toluene and O2 molecule adsorption and activition. Due to the combination of these two factors, 1%Pd/Al2O3-C-H2P displays the best activity among all the samples.