The roles of various plasma species in the plasma and plasma-catalytic removal of low-concentration formaldehyde in air

► Roles of various plasma species in plasma and plasma-catalytic removal of formaldehyde (HCHO) in air were studied. ► Both short- and long-living plasma species contribute to HCHO removal in gas phase. ► O3 does not initiate HCHO removal in gas phase but does over MnOx/Al2O3 catalyst. ► O3 initiated catalytic reactions are mainly responsible for the enhanced HCHO removal by plasma-catalysis. ► The presence of downstream MnOx/Al2O3 catalyst greatly reduces the emission of discharge byproducts (O3) and organic intermediates (HCOOH).