Remarkable promotion effect of trace sulfation on OMS-2 nanorod catalysts for the catalytic combustion of ethanol

Abstract

OMS-2 nanorod catalysts were synthesized by a hydrothermal redox reaction method using MnSO4 (OMS-2-SO4) and Mn(CH3COO)2 (OMS-2-AC) as precursors. SO42−-doped OMS-2-AC catalysts with different SO42− concentrations were prepared next by adding (NH4)2SO4 solution into OMS-2-AC samples to investigate the effect of the anion SO42− on the OMS-2-AC catalyst. All catalysts were then tested for the catalytic oxidation of ethanol. The OMS-2-SO4 catalyst synthesized demonstrated much better activity than OMS-2-AC. The SO42− doping greatly influenced the activity of the OMS-2-AC catalyst, with a dramatic promotion of activity for suitable concentration of SO42− (SO4/catalyst=0.5% W/W). The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), NH3-TPD and H2-TPR techniques. The results showed that the presence of a suitable amount of SO42− species in the OMS-2-AC catalyst could decrease the Mn–O bond strength and also enhance the lattice oxygen and acid site concentrations, which then effectively promoted the catalytic activity of OMS-2-AC toward ethanol oxidation. Thus it was confirmed that the better catalytic performance of OMS-2-SO4 compared to OMS-2-AC is due to the presence of some residual SO42− species in OMS-2-SO4 samples.