Efficient toluene low‐temperature elimination over manganese oxides: Unveiling the decisive role of lattice oxygen

Abstract

Manganese oxide catalysts are considered to be active in the catalytic purification of volatile organic compounds based on two theories. According to one view, defects are mainly constructed to increase the amount of adsorbed oxygen and, consequently, the catalytic activity, whereas the opposite view suggests that the mobility of lattice oxygen is the main reason for determining the catalytic performance. In order to investigate which form of oxygen is the key factor controlling the catalytic performance of manganese oxides, a series of manganese oxide octahedral molecular sieves (OMS‐2) with different adsorption and lattice oxygen properties were synthesized in this study, and the catalytic oxidation performance of the catalysts for toluene was examined. The impact of various oxygen species on the catalytic activity of OMS‐2 was investigated in depth by characterization by Raman, X‐ray diffraction, scanning electron microscope, Brunauer–Emmett–Teller, O2 temperature‐programmed desorption, H2 temperature‐programmed reduction, X‐ray photoelectron spectroscopy, and so forth. It was discovered that OMS‐2‐150 exhibits excellent catalytic activity for toluene purification due to its higher Mn4+ and lattice oxygen as well as low‐temperature reducibility. In addition, in situ diffuse reflectance, infrared Fourier transform spectroscopy also verified that lattice oxygen dominates the reaction and improves the catalytic performance. As such, in contrast to previous investigations, this study found that lattice oxygen migration was more important than adsorbed oxygen content for manganese oxides in the field of volatile organic compounds purification. This brings a new perspective to the preparation of manganese‐based catalysts with promising catalytic behaviors.

Lattice Oxygen Activation Triggered by Ultrasonic Shock Significantly Improves NO Selective Catalytic Reduction

“…As a complementary to O 2 -TPD, H 2 -TPR was measured to assess the effect of bulk-phase defects on the reduction of lattice oxygen species (Figure b). According to the literature reports, the H 2 consumption at high temperature is a direct result of reaction with lattice oxygen . Thus, the two high temperature peaks at regions of 350–400 and 500–600 °C can be ascribed to reduction of surface lattice oxygen and bulk lattice oxygen, respectively .…”

“…According to the literature reports, the H 2 consumption at high temperature is a direct result of reaction with lattice oxygen. 34 Thus, the two high temperature peaks at regions of 350−400 and 500−600 °C can be ascribed to reduction of surface lattice oxygen and bulk lattice oxygen, respectively. 35 It is obvious that after ultrasonic treatment, the profile of α-Fe 2 O 3 exhibited a significant shift to lower temperature, verifying the great promotion of lattice oxygen diffusion due to generation of bulk defects.…”