Defect Engineering on CuMn₂O₄ Spinel Surface: A New Path to High-Performance Oxidation Catalysts

Abstract

Catalytic combustion is an efficient method to eliminate CO and volatile organic compound (VOC) pollutants. CuMn2O4 spinel is a high-performance non-noble metal oxide catalyst for catalytic combustion and has the potential to replace noble metal catalysts. In order to further improve the catalytic activity of CuMn2O4 spinel, we propose a simple and low-cost approach to introduce numerous oxygen and metal vacancies simultaneously in situ on the CuMn2O4 spinel surface for the catalytic combustion of CO and VOCs. Alkali treatment was used to generate oxygen vacancies (VO), copper vacancies (VCu), and novel active sites (VO combines with Mn2O3 at the interface between Mn2O3(222) and CuMn2O4(311)) on the CuMn2O4 spinel surface. In the catalytic combustion of CO and VOCs, the vacancies and new active sites showed high activity and stability. The oxidation rate of CO increased by 4.13 times at 160 °C, and that of toluene increased by 11.63 times at 250 °C. Oxygen is easier to adsorb and dissociate on VO and novel sites, and the dissociated oxygen also more easily participates in the oxidation reaction. Furthermore, the lattice oxygen at VCu more readily participates in the oxidation reaction. This strategy is beneficial for the development of defect engineering on spinel surfaces and provides a new idea for improving the catalytic combustion activity of CuMn2O4 spinel.

Redox-Induced In Situ Growth of MnO2 with Rich Oxygen Vacancies over Monolithic Copper Foam for Boosting Toluene Combustion

“…As displayed in Figure 4c, symmetrical EPR signals at g = 2.003 are observed in both MnO 2 -O v -0.04/CF and MnO 2 /CF, indicating that oxygen vacancies are present in both materials. 36,47 Nevertheless, the intensity of the EPR signal for MnO 2 -O v -0.04/CF is ca. 2.2 times that for MnO 2 /CF, suggesting that MnO 2 -O v -0.04/CF possesses more oxygen vacancies.…”

Local Electron Environment Regulation of Spinel CoMn2O4 Induced Effective Reactant Adsorption and Transformation of Lattice Oxygen for Toluene Oxidation

“…For the CoMn spinel, a broad asymmetrical peak appears in the range of 270−740 °C, indicating that the lattice 4c). However, C 18 O 2 on the CoMn catalyst is not generated at 160 °C but is obviously produced at 200 °C (Figure S27). Based on our previous studies, it is reasonable to conclude that a large amount of bulk oxygen replenished from gaseous oxygen migrates to the surface to form surface lattice oxygen at a higher temperature (200 °C) and then reacts with adsorbed intermediates to form CO 2 .…”

“…Interestingly, the C 18 O 2 and C 18 O 16 O amount of Pt-CoMn varies with the number of pulses, and quantitative analysis shows that the amount of these two species is increased in the fifth pulse (5-p) experiment compared to the first pulse (1-p) experiment (Figure S28). If 18 O 2 is activated only on the Pt species, the amount of C 18 mobility of lattice oxygen in the Pt-CoMn catalyst. These results further suggest that the Pt atom doping into the lattice of CoMn spinel enhances the mobility of lattice oxygen species.…”

“…Volatile organic compounds (VOCs) from residential activities and industrial processes are extremely harmful to the environment and human health. − Catalytic oxidation is considered the most promising method due to its high efficiency and reliability. , However, the core issue of this technology is the development of efficient catalysts that can mineralize VOCs into nontoxic CO 2 and H 2 O at low temperature. − So far, metal oxides have been extensively studied, and significant progress has been made by tuning their compositions, synthesis conditions, and structures. ,− In the spinel AB 2 O 4 structure, A and B metal ions are located at tetrahedron and octahedron sites, respectively, and both sites can be adjusted by metals to obtain excellent catalytic performance. − Our previous work has found that spinel (CoMn 2 O 4 ) completes the reaction via oxygen cycling between gaseous oxygen, bulk oxygen, and surface oxygen, which is obviously different than supported oxides (Co 3 O 4 /MnO x ) . However, the migration of bulk lattice oxygen to surface lattice oxygen in spinel CoMn 2 O 4 requires a higher temperature and limits further improvement of low-temperature activity.…”

Expediting Ethylbenzene Oxidation via a Bimetallic Cobalt–Manganese Spinel Structure with a Modulated Electronic Environment

“…Despite the endeavors spanning the past several decades, development of a suitable catalyst remains the key to attaining this goal. A careful literature survey leads us to the finding that Co- and Mn-based catalysts are generally shown to be effective catalysts for oxidation reactions. − Provoked by the aforementioned discussions, it is rationally anticipated that the Co–Mn-based spinel can be a potential good catalyst for the selective oxidation of EB. Hence, we herein report that (Co,Mn)(Co,Mn) 2 O 4 (denoted as CMO) prepared by a facile sol–gel method can act as an efficient catalyst for the selective solvent-free aerobic oxidation of EB.…”