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CuO/CeO2 catalysts were widely studied as an alternative to precious metal catalysts, and the Cu–Ce synergy was essential to improve the catalytic performance. In this paper, the effects of CuO loading on Cu–Ce synergy in CuO/CeO2 nanorod catalysts and their performance in toluene combustion were systematically investigated. It was found that non-equilibrium plasma facilitated the dispersion of CuO active species on the CeO2 surface. With the increase of the CuO loading from 1 wt% to 4 wt%, the Cu–Ce synergistic effect was gradually improved, which generated Cu+/Cu2+ and Ce3+/Ce4+ redox electron pairs. The highest oxygen vacancy concentration and Cu+ content of CuCe-4 (4 wt%) resulting from strong Cu–Ce synergy accelerated the activation of chemisorbed oxygen and consequently improved the efficiency of toluene catalytic combustion. [ABSTRACT FROM AUTHOR]

Plasma catalysis is recognized as a promising technology for the elimination of diluted volatile organic compounds (VOCs). In this study, a hybrid process was carried out using dielectric barrier discharge (DBD) and MCeZr/TiO2 (M = Cu, Mn, Ni, and Co) catalysts for the degradation of VOCs. The plasma-catalytic system demonstrated a substantial improvement in toluene conversion and CO2 selectivity compared to the plasma-only system owing to the synergistic effects of plasma and thermal catalysis on toluene degradation. The performance of toluene removal follows the sequence of CuCeZr/T > NiCeZr/T > CoCeZr/T > MnCeZr/T in plasma catalysis. The CuCeZr/T catalyst demonstrated the highest toluene conversion of 99.0% and a CO2 selectivity of 91.0% at a discharge power of 30 W. Energetic electrons and reactive species generated by plasma actively participate in toluene activation in the gas phase and facilitate adsorption on the catalyst surface. The redox properties between Ce4+/Ce3+ and Cu+/Cu2+ species dictated the reducibility of the CuCeZr/T catalyst, promoting oxygen cycling during toluene oxidation and leading to enhanced catalytic performance. The pathways of toluene destruction in the plasma-catalysis system are discussed based on the analysis results of GC–MS, optical emission spectroscopy and calculations of the electron-impact reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Utilizing Bacterial Cellulose as a Pore-Forming Agent to Synthesize Multi-Layered, Multi-Porous Composite Metal Oxide Catalysts. • Bacterial Cellulose Mitigates Environmental Risks and Cost in Catalyst Preparation. • In-Depth Analysis Reveals How the Pore Structure Created by Cellulose Pore-Forming Agent Enhances Catalytic Activity. Utilizing environmentally-friendly bacterial cellulose as a scaffold, a highly porous, layered OA-BC catalyst was synthesized through an enhanced sol-gel process. This catalyst demonstrated exceptional performance in the oxidation of toluene, outperforming conventional alternatives that utilize chemical porogens. The OA-BC catalyst efficiently degrades toluene at 220℃ with high stability and hydrophobicity, indicating resistance to deactivation. Its superior activity is due to increased oxygen vacancies, enhanced metal oxide cooperation, and a layered porous structure, which together enhance active oxygen species and oxygen diffusion. Calcination of the OA-BC catalyst results in molecular cleavage and formation of small aggregates, increasing hydroxyl groups that stabilize Cu and Ce centers, enhancing toluene-oxygen reactions. In-situ infrared and X-ray photoelectron spectroscopy confirm stable monodentate Cu+ ligands, contributing to its high catalytic activity. This study introduces a novel approach by employing bacterial cellulose as a template for synthesizing a porous stratified OA-BC catalyst, demonstrating superior performance in toluene oxidation. The efficacy of catalyst results from a tripartite synergy involving the stratified porous architecture, the stabilizing effect of Cu+-coordinating ligands and hydroxyl groups, and the interplay of hydroxyl electron donors and acceptors, shedding light on environmentally benign catalyst development. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The catalytic self-sustained combustion of toluene was successfully developed. • CuCeZr/TiO 2 catalyst showed the excellent performance in self-sustained combustion. • TPO in N 2 atmosphere was used to investigate the role of lattice oxygen in toluene combustion. Abstract The catalytic self-sustained combustion of toluene over Cu x Mn 1-x Ce 0.75 Zr 0.25 /TiO 2 catalysts (x = 1, 0.5, 0) was studied in a microscale combustor. The catalytic activity is determined not only by the temperature with toluene conversion of 90% (T co), but also by the corresponding lean-combustion limits. It was found that the self-sustained combustion was achieved successfully over the catalysts, with the toluene concentrations of 0.35 con.%, 0.50 con.% and 1.00 con.%. According to T co, the activity decreased in the order of CuCe 0.75 Zr 0.25 /TiO 2 (234 °C)＞Cu 0.5 Mn 0.5 Ce 0.75 Zr 0.25 /TiO 2 (238 °C) ＞MnCe 0.75 Zr 0.25 /TiO 2 (284 °C). The excellent activity of CuCe 0.75 Zr 0.25 /TiO 2 catalyst could be ascribed to the high content of active lattice oxygen, good low-temperature reducibility and homogeneous dispersion, combined with the results of H 2 -TPR, O 2 -TPD and XPS. Furthermore, the results of in-situ DRIFT and temperature-programmed oxidation (TPO) of toluene in N 2 atmosphere suggested that toluene was adsorbed on the catalyst surface by removing α-H from methyl and combining with active oxygen specie to form benzyl group, which was finally oxidized into CO 2 and H 2 O with lattice oxygen. [ABSTRACT FROM AUTHOR]

• Ea of intermediate species is calculated during toluene oxidation. • Relationship between the activation energy of the overall and primitive reaction. • Transient response experiments of isotopically labeled oxygen. • M−K mechanism dominates in the oxidation of toluene. Catalytic properties of multiple metals deposited on TiO 2 nanoparticles were investigated in the oxidation of toluene. Isovolume impregnation method prepared the catalysts containing Cu, Mn, Ni, Co, and Fe deposited on TiO 2 , including CeO 2 and ZrO 2. The effects of loaded metal oxides on the structure and activity of initial catalysts were investigated using various characterization techniques. Toluene's removal efficiency and CO 2 selectivity in the catalyst system were classified as follows: CuCeZr/T > MnCeZr/T > NiCeZr/T > CoCeZr/T > FeCeZr/T. Presence of water vapor exhibits an inhibitory effect on the conversion of toluene, which diminishes at higher temperatures. One contribution of this paper is to obtain the oxidation pathway of toluene and the relationship between the activation energy of all-inclusive and elementary reactions based on the variation of infrared spectrum using Freeman-Carroll method. Another contribution is to clarify the share of Langmuir-Hinshelwood and Mars-van Krevelen mechanisms during the oxidation of toluene over CuCeZr/T catalyst by transient response experiments of isotopically labeled oxygen. These findings provide a feasible method for the design and synthesis of transition metal oxide catalysts for industrial applications. [ABSTRACT FROM AUTHOR]