A non-noble-metal bifunctional catalyst with efficient and durable activity towards both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is crucial to the development of ...rechargeable Zn-air batteries. Herein, a facile one-step hydrothermal method is reported for the synthesis of a high-performance bifunctional oxygen electrocatalyst, cobalt-doped Mn3O4 nanocrystals supported on graphene nanosheets (Co–Mn3O4/G). Compare to pristine Mn3O4, this Co–Mn3O4/G exhibits greatly enhanced electrocatalytic activity, delivering a half-wave potential of 0.866 V for the ORR and a low overpotential of 275 mV at 10 mA cm−2 for the OER. The zinc-air battery built with Co–Mn3O4/G shows a reduced charge–discharge voltage of 0.91 V at 10 mA cm−2, an power density of 115.24 mW cm−2 and excellent stability without any degradation after 945 cycles (315 h), outperforming the state-of-the-art Pt/C–Ir/C catalyst-based device.
A facile one-step hydrothermal method is reported for the synthesis of high-performance bifunctional oxygen electrocatalyst, cobalt doped Mn3O4 nanocrystals supported on graphene nanosheets (Co–Mn3O4/G). Compare to pristine Mn3O4, this Co–Mn3O4/G exhibits a greatly enhanced electrocatalytic activity, delivering a half-wave potential of 0.866 V for ORR and a low overpotential of 275 mV at 10 mA cm−2 for OER. Display omitted
A novel amino-functionalized silica-coated nanoscale zerovalent iron (NZVI@SiO2-NH2) was successfully synthesized by using one-step liquid-phase method with the surface functionalization of nanoscale ...zerovalent iron (NZVI) to enhance degradation of chlorinated organic contaminants from anaerobic microbial system. NZVI@SiO2-NH2 nanoparticles were synthesized under optimal conditions with the uniform core-shell structure (80–100 nm), high loading of amino functionality (~0.9 wt%), and relatively large specific surface area (126.3 m2/g). The result demonstrated that well-dispersed NZVI@SiO2-NH2 nanoparticle with nFe0-core and amino-functional silicon shell can effectively remove 2,4,6-trichlorophenol (2,4,6-TCP) in the neutral condition, much higher than that of NZVI. Besides, the surface-modified nanoparticles (NZVI@SiO2-NH2) in anaerobic granule sludge system also showed a positive effect to promote anaerobic biodechlorination system. More than 94.6% of 2,4,6-TCP was removed from the combined NZVI@SiO2-NH2-anaerobic granular sludge system during the anaerobic dechlorination processes. Moreover, adding the appropriate concentration of NZVI@SiO2-NH2 in anaerobic granular sludge treatment system can decrease the toxicity of 2,4,6-TCP to anaerobic microorganisms and improved the cumulative amount of methane production and electron transport system activity. The results from this study clearly demonstrated that the NZVI@SiO2-NH2/anaerobic granular sludge system could become an effective and promising technology for the removal of chlorophenols in industrial wastewater.
A novel amino-functionalized silica-coated nanoscale zerovalent iron (NZVI@SiO
2
-NH
2
) was successfully synthesized by using one-step liquid-phase method with the surface functionalization of ...nanoscale zerovalent iron (NZVI) to enhance degradation of chlorinated organic contaminants from anaerobic microbial system. NZVI@SiO
2
-NH
2
nanoparticles were synthesized under optimal conditions with the uniform core-shell structure (80–100 nm), high loading of amino functionality (~0.9 wt%), and relatively large specific surface area (126.3 m
2
/g). The result demonstrated that well-dispersed NZVI@SiO
2
-NH
2
nanoparticle with nFe
0
-core and amino-functional silicon shell can effectively remove 2,4,6-trichlorophenol (2,4,6-TCP) in the neutral condition, much higher than that of NZVI. Besides, the surface-modified nanoparticles (NZVI@SiO
2
-NH
2
) in anaerobic granule sludge system also showed a positive effect to promote anaerobic biodechlorination system. More than 94.6% of 2,4,6-TCP was removed from the combined NZVI@SiO
2
-NH
2
-anaerobic granular sludge system during the anaerobic dechlorination processes. Moreover, adding the appropriate concentration of NZVI@SiO
2
-NH
2
in anaerobic granular sludge treatment system can decrease the toxicity of 2,4,6-TCP to anaerobic microorganisms and improved the cumulative amount of methane production and electron transport system activity. The results from this study clearly demonstrated that the NZVI@SiO
2
-NH
2
/anaerobic granular sludge system could become an effective and promising technology for the removal of chlorophenols in industrial wastewater.
Display omitted
•Hollow spherical ZIF-8 decorated ZnO/SiO2 photocatalysts was successfully constructed.•ZIF-8/ZnO/SiO2 hollow spheres display outstanding visible light catalytic ...activities.•Remarkable photocatalytic removal for organic dyes and Cr (VI) was achieved.•The Z-scheme heterojunction reduces band gap and facilitates carrier separation efficiency.•Hollow sphere structures enhance the absorption efficiency of solar light.
The zeolitic imidazolate framework-8 (ZIF-8) demonstrates promising photocatalytic activity in wastewater treatment. Nevertheless, limited visible light utilization and arduous recyclability hinder its practical application. Herein, we fabricated ZIF-8 decorated zinc oxide/silica (ZnO/SiO2) hollow spheres by an in-situ strategy. This composite effectively photocatalytically degrades organic dyes and reduces Cr (VI) under the simulated sunlight. Results reveal that Z-scheme heterojunction construction between ZIF-8 and ZnO/SiO2 is formed and facilitates the effective separation and transport of electrons and holes, leading to nearly complete methylene blue (MB) degradation, 88.7 % of rhodamine B (RhB) removal, and 41.8 % Cr (VI) reduction within 30 min. Notably, the ZIF-8/ZnO/SiO2 composite exhibits enhanced visible-light utilization attributed to its reduced band gap (3.04 eV), thereby improving MB degradation compared to using solely ultraviolet light. Furthermore, the composite demonstrates remarkable reusability and stability, achieving over 99 % removal rate for MB after four photocatalysis cycles with minimal structural and morphological changes. This work demonstrates the remarkable photocatalytic activity ZIF-8/ZnO/SiO2 with its improved visible-light response, highlighting the potential of using modified ZIF-8 materials as promising and sustainable catalysts for wastewater treatment.
Display omitted
•Activated carbon supported monodispersed Co3O4 nanoparticles (Co3O4/AC) were prepared via a facile deposition method.•The presence of Co-OH+ on Co3O4/AC is highly efficient in PMS ...activation for gaseous toluene degradation.•SO4− play a dominant role for toluene degradation, HO derived from PMS activation can improve carbon mineralization.•Few gaseous intermediates were discharged during reaction process.
Gas-phase VOCs decomposition generally produces intermediates and causes secondary air pollution. To avoid this issue, we proposed a novel method for a typical gaseous VOC (toluene) degradation via catalytic activation of peroxymonosulfate (PMS) in the liquid phase. Herein, activated carbon supported monodispersed Co3O4 nanoparticles (Co3O4/AC) were prepared via a facile deposition method. It is highly efficient in PMS activation for toluene degradation due to the presence of Co-OH+ species and well dispersed Co3O4 on Co3O4/AC. A toluene removal efficiency of nearly 90% was maintained during the reaction, and few gaseous intermediates were discharged. Sulfate radical (SO4−) and hydroxyl radical (HO) derived from PMS activation played different roles during toluene oxidation and mineralization. Electron spin resonance (EPR) suggested that the generation of plentiful SO4− resulted in the superior toluene degradation, and the presence of HO can improve carbon mineralization. Radical quenching tests further confirmed that SO4− played a dominant role for toluene degradation, whereas the absence of HO inhibited the carbon mineralization. The toluene degradation pathway in the Co3O4/AC-PMS system was proposed based on the intermediates identified by GC–MS.
Display omitted
•Mn-xCe/ZSM-5 was successfully fabricated and cooperated well with VUV irradiation.•Mn-3Ce/ZSM-5 exhibited superior toluene removal efficiency (93%) in VUV-PCO process.•O3 can be ...completely removed and simultaneously enhance toluene removal efficiency.•Increase of oxygen vacancies benefit adsorption and catalytic decomposition of O3.
Volatile organic compounds (VOCs) are one of the most important precursors to form the fine particulate matter and photochemical smog, and should be strictly controlled. Vacuum ultraviolet (VUV) photolysis has provided a facile and an effective way to remove VOCs due to its powerful oxidation capability under mild reaction conditions. However, VUV irradiation would generate ozone which brings about secondary pollution. In this study, ZSM-5 supported Mn-Ce mixed oxides (Mn-xCe/ZSM-5) were fabricated as efficient catalysts for ozone catalytic oxidation (OZCO) process, which were applied in combination with VUV photolysis to remove O3 byproduct and simultaneously facilitate toluene oxidation. The results indicated that the Mn-3Ce/ZSM-5 catalyst considerably enhanced the catalytic degradation efficiency up to 93% for the gas-phase toluene, one of the hazardous VOCs. Meanwhile, almost all the O3 by-product could be eliminated in the process. It was found that the strong interaction of the MnOCe bond and the variable chemical valence of Mn and Ce based species in the mixed oxides would tune the redox capacity of Mn-xCe /ZSM-5. An increase in surface Ce3+ species and surface density of oxygen vacancies would benefit the adsorption and catalytic transformation of O3 which eventually form the reactive oxygen species over Mn-xCe/ZSM-5.
VUV photolysis presents a simple process for VOCs degradation, while the poor mineralization rate and extensive by-products greatly limit its application. In this study, the contribution and synergy ...between •OH and •O2− to toluene degradation in the VUV-based process were comprehensively investigated by controlling water and oxygen in the gas flow. It was found that •OH promoted the initial degradation of toluene and macromolecular intermediates, while •O2− dominated toluene mineralization by boosting the formation of small molecules and CO2. Compared with the •OH-dominated VUV photolysis, the presence of catalyst greatly changed the degradation pathway, promoted toluene mineralization into CO2 and reduced health toxicity via promoting •O2− formation. This study originally focuses on the key role of •O2− in VOCs deep oxidation and provides an effective strategy to boost its clean mineralization via the VUV-based process.
Display omitted
••OH mainly promotes the initial degradation and ring-opening of toluene in VUV system.••O2− is essential to toluene mineralization into small molecules and CO2.••O2− and •OH well cooperate in deep toluene oxidation in the VUV system.•The increased •O2− produced by catalyst greatly promotes toluene mineralization and reduces health toxicity.
PDF
