Search

Mn-based catalysts present enormous potential for plasma oxidation of toluene in air. Bimetallic Mn-M (M= Cu Co Ce Sm) active components were loaded on the ZSM-5 zeolites to prepare new catalysts for toluene degradation. These new catalysts were characterized using SEM, XRD, XPS, H 2 -TPR, N 2 adsorption-desorption, etc. They were also evaluated in terms of the catalytic activity and the critical operating factors using a plasma reactor. It shows that adding the auxiliary metal to Mn/ZSM-5 can substantially enhance the degradation efficiency. Taking the most active catalyst Mn-Ce/ZSM-5 as an example, the toluene conversion and CO 2 selectivity could reach 94.5 % and 96.1 % at an initial concentration of 1000 ppm and specific input energy of 9 kJ/L. When compared to the Mn/SZM-5, the bimetallic catalyst's toluene conversion and CO 2 selectivity increased by 11 % and 4.5 %, respectively. Theoretical simulation of density functional theory was employed to reveal that the charge is rearranged after introducing oxygen vacancy by doping, and the adsorption of toluene on the catalyst becomes easier. It is worth mentioning that in the simulation process, a new Y-type ZSM-5 model is used in this work. This is an aperiodic model closer to reality. The combination of plasma and catalyst could have a stabilizing effect on the existence of oxygen vacancy. [Display omitted] • A new Y-type ZSM-5 model is used in the DFT simulation process in this work. • Long term stable catalyst oxygen vacancy in NTP atmosphere. • Auxiliary metals adding to the active components increased O vacancy concentration. • Illustrating the effects of SIE, residence time and concentration on C 7 H 8 removal. [ABSTRACT FROM AUTHOR]

The crux to promote the utilization of air-cathode microbial fuel cell (AC-MFC) is to find high-efficiency and low-budget oxygen reduction reaction (ORR) catalysts, which can replace Pt-based catalysts, reduce electrode cost and thus improve the cost-effectiveness of AC-MFC. In this work, a three-dimensional network carbon structure F-MIL-HOF loaded with Fe 2 O 3 material composites have been successfully synthesized by carbonizing by NH 4 F-fluorinated MIL-88B combined with a high nitrogen content hydrogen-bonded organic framework (HOF) to evince excellent catalytic property for ORR in both alkaline and neutral electrolytes. The Fe 2 O 3 obtained after carbonization of MIL-88B portrays efficient ORR catalytic activity, and the combination with the natural pore-rich HOF precisely solves the problems of uncontrolled growth and agglomeration during Fe 2 O 3 synthesis, achieving the high dispersion and full exposure of Fe 2 O 3 nanoparticles as active sites. As-synthesized F-MIL-HOF as cathodic catalyst reaches a limiting current density of 6.40 mA cm−2 in alkaline condition, which exhibits an advantage performance over commercial Pt/C (6.26 mA cm−2). Furthermore, F-MIL-HOF shows approximately four-electron pathway with better methanol resistance and stability than Pt/C, and the performance only decreases by 10.2 % in the stability test, which still had efficient ORR catalytic performance. F-MIL-HOF is an emerging alternative electro-catalyst for AC-MFC. • F-MIL-HOF is an F-modified Fe–N–C material. • MIL-88B pyrolysis produces Fe 2 O 3 active sites to promote mass transfer. • F modification increases the stability and corrosion resistance of F-MIL-HOF. • The synergistic effect of F and N element can reduce the activation barrier. • F-MIL-HOF has outstanding ORR performance in MFC compared with Pt/C. [ABSTRACT FROM AUTHOR]

The metal-free carbon-based catalyst with low cost and high oxygen reduction reaction (ORR) activity is urgently desired to satisfy the demands of microbial fuel cells (MFCs). However, it is still a great challenge to develop a facile and feasible strategy to construct efficient active sites of heteroatom doping for carbon-based electrocatalyst. Herein, we report a strategy based on an ammonium fluoride (NH 4 F) gas-steamed metal-organic frameworks (MOFs) to heighten structural defects and density of N, F active sites of metal-free catalyst. Oxygen temperature-programmed deposition and density functional theory results confirm that the NH 4 F gas-steamed process greatly enhances the adsorption affinity of O 2 and oxygen intermediates on the catalysts. The resulted N and F co-doped porous carbon cage (FNC-15) demonstrates outstanding ORR catalytic activity and long-term stability in alkaline and neutral electrolytes. This work proposes a facile and efficient in situ gas-steamed strategy to develop metal-free cathode catalysts with superior performance. [Display omitted] • NH 4 F gas-steamed strategy introduce defects and N, F active sites within catalysts. • Defect sites enhance the oxygen molecules adsorption affinity of catalysts. • Remarkably enhanced ORR catalytic activity and stability. • The metal-free FNC-15 exhibits superior performance in microbial fuel cell. [ABSTRACT FROM AUTHOR]

In this work, CeMn 1-x M x O 3 (M = Cu, Fe and Co) perovskites were synthesized and used as efficient heterogeneous catalyst for degrade of tetracycline chloride (TC-HCl) via photocatalysis coupled peroxymonosulfate (PMS) oxidation under visible-light illumination. Metal doping significantly improved the catalytic activity of perovskites. The CeMn 0.6 Co 0.4 O 3 /PMS/Vis system demonstrated excellent performance that 96.4% of 60 mg/L of TC-HCl was degraded within 30 min with a high reaction rate constant of 0.136 min−1, which is about 4.3 times higher than that of CeMnO 3 , and almost 4.4 times higher than that of pure PMS. Results confirmed the addition of Co led to mixed valence states of Mn (III)/Mn (Ⅳ) and Co (II)/Co (III) in the perovskite structure, promoting the electron transfer from the CeMn 0.6 Co 0.4 O 3 to PMS. Moreover, CeMn 0.6 Co 0.4 O 3 exhibited good stability over a wide pH range (3.0–11.0). The rapid transformation of Co (II)/Co (III) redox pairs is critical for PMS activation as the limiting step. Superoxide radicals (•O 2 −), electron (e−) and sulfate radical (SO 4 −•) were the dominant oxidative species responsible for removing TC-HCl. This work proposed some new insights to understand the heterogeneous reaction mechanism during PMS oxidation and photocatalytic process and promote the development of perovskites catalyst for removal of organic pollutants. [Display omitted] • Co doping promote cycles of Co2+/Co3+, Mn3+/Mn4+ and formation of oxygen vacancies. • •O 2 −, e− and SO 4 −• are primary radicals for catalytic degradation of TC-HCl. • Coupling of photocatalysis and PMS oxidation improved catalytic activity. • Vis/CeMn 0.6 Co 0.4 O 3 /PMS system degraded 96.4% TC-HCl within 30 min. [ABSTRACT FROM AUTHOR]

Stable perovskite oxide is considered as a potential cathode for microbial fuel cells (MFCs). Herein, Zn is used as an effective element to modify the micro-structure and oxygen vacancy of perovskite to be a novel cathode catalyst. Physical characterizations show that due to partial volatilization at high temperature of Zn, perovskite forms hierarchically porous structures. Moreover, Zn is precipitated in electrochemical reaction to generate Zn vacancy in situ; thus, the active center of Fe has a superior interaction with oxygen-containing species, promoting the production of oxygen vacancy and forms a mixed valence state of Fe2+/Fe3+. The Zn-doped perovskite material CaFe 0·7 Zn 0·3 O 3 exhibits remarkable oxygen reduction reaction (ORR) performances with outstanding onset potential (0.194 V vs. Ag/AgCl) and half-wave potential (−0.219 V vs. Ag/AgCl) under alkaline condition, which is better than Pt/C catalyst. Besides, CaFe 0·7 Zn 0·3 O 3 shows an excellent four-electron pathway of ORR mechanism with remarkable corrosion resistance and stability, which enables a more reliable cathode electrocatalyst. The maximum power density of CaFe 0·7 Zn 0·3 O 3 (892.10 ± 90.79 mW m−3) testing on microbial fuel cell is comparable to the maximum power density (1012.86 ± 84.03 mW m−3) of Pt/C. The findings of this work provide the feasibility of exploring inexpensive and high-performance cathode catalyst. Image 1 • Zn-doped CaFeO 3 promotes mesoporous formation. • The incorporation of Zn creates more oxygen vacancies. • CaFe 0·7 Zn 0·3 O 3 shows the remarkable catalytic activity and stability during ORR. • Applying as the cathode catalyst in microbial fuel cells. [ABSTRACT FROM AUTHOR]