Search

• H-MIL-53 with oxygen vacancy was prepared by ligand selective pyrolysis. • Synergistic effect of photocatalysis and Fenton. • Oxygen vacancy accelerates •O 2 − by increasing electron hole separation. • Unsaturated coordination iron accelerates H 2 O 2 to produce •OH. The combination of Fenton catalyst and photocatalyst will lead to the decrease in light absorption on the photocatalyst, and it is difficult for Fe3+ to be converted into Fe2+on the Fenton catalyst, resulting in poor Fenton-like process and photocatalysis effect. Preparing catalysts containing oxygen vacancies (OVs) can simultaneously increase the light absorption and the cycle of Fe(Ⅲ) to Fe(Ⅱ) to improve the catalytic efficiency of Fenton-like process and photocatalysis. A mesoporous H-MIL53 with OV was constructed by ligand selective pyrolysis. The formation mechanism of H-MIL-53 vacancy was analyzed by XPS, EPR, FTIR and TG. XPS, EPR, FTIR and TG showed that calcination caused the fracture of Fe-O bond resulted in OV and coordinative unsaturated Fe site. H-MIL-53 showed higher degradation efficiency of tetracycline hydrochloride (93%) and high recycling performance. The electron-rich OV could activate the dissolved oxygen to produce •O 2 − through phot-introduced electrons, while the electron-poor iron site can activate H 2 O 2 to produce •OH. These results provide a new direction for the construction of metal-organic framework (MOF) containing OV for application in Fenton-like process and photocatalysis. [Display omitted] [ABSTRACT FROM AUTHOR]

• CuCo-based MOF was prepared via a facile solvothermal method. • CuCo-MOF displays excellent activity for NIM degradation. • The synergy between the Cu-Co dual active centers enhanced the activation of PMS. • The NIM reaction site was revealed and its degradation path was proposed. • Cu and Co dual active sites to favor Cu and Co-PMS adsorption and charge transfer. Regulation of active sites is of significant importance for boosting the catalytic properties of metal–organic frameworks (MOF). Herein, we developed a one-pot strategy to construct bimetallic organic frameworks with Cu-Co double sites (CuCo-MOF) for peroxymonosulfate (PMS) activation. CuCo-MOF exhibits excellent active oxidation capacity, enabling complete removal of NIM within 25 min (0.227 min−1). Its NIM degradation rate was 7.3 and 2.4 times higher than that of Cu-MOF and Co-MOF, respectively. The theoretical simulations unravel that doping Co into the lattice structure of Cu-MOF promotes electron transfer from the electron-rich region (benzene ring) to the electron-deficient regions around metal sites, which facilitated the optimization of the adsorption energy for PMS activation and boosted the breakage of O O bond in PMS. According to LC-MS analysis and DFT calculation, the NIM degradation pathways were proposed, and its degradation intermediates were conducted for toxicity evaluation. The findings, revealing the synergistic effect of bimetals, open a new avenue for the rational design of highly efficient MOF-based Fenton-like catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preparation of NC-Co(PO 3) 2 adopted facile gas-solidified phosphating strategy. • NC-Co(PO 3) 2 electrode was used for the first time in the field of CDI. • NC-Co(PO 3) 2 showed better electrosorption capacity of 95.41 mg g−1. • NC-Co(PO 3) 2 had excellent selectivity in various ion-competitive environments. • Real copper-containing wastewater confirmed the great potential of NC-Co(PO 3) 2. The increasing amount of heavy metal copper ions (Cu2+) in industrial emissions, poses a serious threat to human health, biological environment, and resource scarcity. Capacitive deionization (CDI) is considered as a green and efficient method for desalination. It is crucial to develop high-performance electrodes for efficient operation of CDI that go beyond conventional carbon and yield considerable environmental benefits. Here, metal organic frameworks (MOFs) derived carbon-loaded cobalt metaphosphate (NC-Co(PO 3) 2) was prepared by low-temperature gas–solid phosphating for Cu2+ removal as CDI electrode for the first time. NC-Co(PO 3) 2 demonstrated superior electrode structure and function due to the synergistic effects of electric double layer coupling P-O bonds, the binding tendency of metaphosphate groups with Cu2+, and interfacial redox reactions induced by the labile valence state of cobalt. The optimal electrosorption capacity of NC-Co(PO 3) 2 was 95.41 mg g−1 at 1 V in 50 mL Cu2+ solution with splendid cyclic regeneration capability. Moreover, NC-Co(PO 3) 2 exhibited excellent selectivity and outstanding electrosorption performance in the presence of multiple coexisting ions and this CDI system realized the purification of actual copper-containing wastewater. A series of characterizations further revealed the specific mechanism of Cu2+ in adsorption–desorption process. Our finding strongly supported NC-Co(PO 3) 2 electrode can extend the CDI platform's capability for effectively removing and retrieving Cu2+ from wastewater. [ABSTRACT FROM AUTHOR]

As a promising energy storage/conversion technology, the microbial fuel cell (MFC) is generally restricted by the biofouling on the cathode and the sluggish kinetics of oxygen reduction reaction (ORR). Consequently, developing bacteriostatic and high-performance ORR catalysts is critical for the large-scale application of MFC. Herein, we prepare an electrocatalyst of porous octahedral zirconium-based metal organic framework (MOF) UiO-66-NH 2 with dispersed Ag and Fe 3 C nanoparticles (Ag/Fe–N–C) through a facile impregnation and pyrolysis method for an efficient alkaline and neutral ORR. Systematic experimental results demonstrate that the synergistic effect of Ag and Fe can optimize the d-band center of catalyst to boost the interfacial charge transfer, thus resulting in an increased ORR kinetics. As expected, the catalyst with Ag/Fe–N–C-2:1 exhibits outstanding onset potential (1.01 V vs. RHE) and half-wave potential (0.58 V vs. RHE) in neutral electrolyte, which is comparable to Pt/C catalyst. Meanwhile, Ag/Fe–N–C-2:1 indicates obvious antibacterial activity, inhibiting the biofouling on the cathode surface. The MFC with the Ag/Fe–N–C-2:1 as the cathode catalyst can achieve a maximum power density of 1261.1 ± 24 mW m−3, outperforms the MFC with Pt/C (1087.5 ± 14 mW m−3). In summary, Ag/Fe–N–C-2:1 composite can serve as a feasible alternative cathode catalyst for MFC. [Display omitted] • Efficient ORR catalysts based on UiO66-NH 2 with dispersed Ag and Fe 3 C nanoparticles. • Bimetallic active sites optimize the d-band center and promote charge transfer. • High ORR catalytic activity and antibacterial performance. • As bacteriostatic ORR catalyst applied to the air-cathode microbial fuel cell. [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]

The oxygen reduction reaction (ORR) kinetics are well known to strongly rely on the activives of electrocatalysts. Herein, a Fe-N-doped porous carbon-based electrocatalyst combined with zinc (Zn) -based metal-organic frameworks (MOFs) (Fe x -N@MOF) was designed and successfully fabricated via a facile process combined immersion doping and pyrolysis. By controlling the formation of Fe 3 C, the physical structure of porous carbon was significantly altered, and the active chemical sites of Fe species can be formed to catalyze ORR. The uniform N-doped three-dimensional interpenetrating network structure yielded a high surface area. Both Fe 3 C and Fe-N x could offer an abundance of active sites and thus promoted Fe 0.05 -N@MOF to exhibit high ORR activity in alkaline, neutral and acid electrolytes. Fe 0.05 -N@MOF showed extraordinary stability and methanol tolerance under a varied pH range conditions, it could be applied as cathode electrocatalyst in different fuel cells such as Zn-air fuel cell (ZFC), microbial fuel cells (MFCs), as well as direct methanol fuel cell (DMFC). Fe 0.05 -N@MOF is a promising material to replace Pt-based electrocatalysts as non-precious metal catalysts. [Display omitted] • The synergistic catalysis of Fe-N x and Fe 3 C on oxygen reduction reaction. • The transformation of carbon spheres to nanotubes was regulated by Fe species. • High electrocatalytic activity in alkaline, neutral and acidic media. • As cathode catalyst was applied to the various fuel cells. [ABSTRACT FROM AUTHOR]

Exploiting a facile way to synthesize low-cost and high-performance oxygen reduction reaction (ORR) catalysts is a core issue in microbial fuel cells (MFCs). Hence, a facile and extensible method has been developed to prepare efficient ORR catalysts by using robust UiO-66 as a precursor, modified with melamine and trithiocyanuric via the impregnation method. Benefiting from the hierarchical structure of UiO-66, the NS@UiO-66 has excellent stability, more active sites and improved mass transfer. Significantly, the half-wave potential and the current density of the NS@UiO-66 are 0.546 V vs. RHE and 6.19 mA cm−2 respectively, which is better than that of benchmark Pt/C in neutral conditions. Furthermore, the power density of MFCs assembled with the NS@UiO-66 catalyst is 318.6 ± 2.15 mW m−2. The density functional theory calculation demonstrates that the reaction barrier can be reduced effectively for accelerating the ORR process through the synergistic effect of N and S. The NS@UiO-66, as an ideal candidate to substitute for the commercial Pt/C counterpart, is expected to promote the scaling-up production and application of MFCs due to low-cost elements doping and facilely synthetic method. [Display omitted] • A facile synthesis way for preparing NS@UiO-66 porous carbon is proposed. • UiO-66 is a stable platform exposing more active sites and boosting mass transfer. • N, S co-doping induces charge redistribution and reduces the activation barrier. • The stable NS@UiO-66 shows great ORR property and application prospects in MFCs. [ABSTRACT FROM AUTHOR]

In this work, magnetic Fe 3 O 4 /MIL-125 nanoparticles were prepared by hydrothermal method and used as a heterogeneous catalyst for the removal of tetracycline hydrochloride. The Fe 3 O 4 /MIL-25 composite exhibits an enhanced degradation percentage of tetracycline hydrochloride via heterogeneous Fenton-like process and photocatalysis. At optimal conditions, 97% of tetracycline hydrochloride (50 ppm) can be degraded in 50 min with hydrogen peroxide under ultraviolet light. The Fe 3 O 4 /MIL-125 can be easily separated from solution and exhibit excellent reusability and stability. The degradation percentage of tetracycline hydrochloride still reaches 85% after four cycles of reuse. Further radical inhibition experiments confirmed that •OH and •O 2 − formed and function in the photo-Fenton system. The electron spin resonance also confirms this view. These results show that magnetic Fe 3 O 4 /MIL-125 under ultraviolet light irradiation increases photo-generated electronic transfer through enhancing Fe(III)/Fe(II) cycle to generate more hydroxyl radical. Accordingly, the degradation percentage of the target pollutant is significantly improved. [Display omitted] • MIL-125 by electronic transfer improves the cycle of Fe(Ⅲ)/Fe(Ⅱ) in Fenton systems. • The photo-generated electrons excited by UV are the source of •O 2 − formation. • MIL-125 stimulated by UV promotes Fe2+ production and increases •OH production. • Fe 3 O 4 /MIL-125 can separate from the reaction medium by an external magnetic field. [ABSTRACT FROM AUTHOR]

As a promising energy conversion equipment, the performance of microbial fuel cell (MFC) is affected by slow kinetics of oxygen reduction reaction (ORR). It is of great significance to explore electrocatalysts with high activity for sustainable energy applications. Herein, we synthesize the in-situ grown carbon nanotubes decorated electrocatalyst derived from copper-based metal organic frameworks (MOFs) co-doped with cobalt and nitrogen (CuCo@NCNTs) through straightforward immersion and pyrolysis process. The carbon nanotubes produced by metallic cobalt and high-activity bimetallic active sites formed by nitrogen doping enable CuCo@NCNTs to have the best oxygen reduction reaction (ORR) performance in alkaline electrolyte, with limit current density of 5.88 mA cm−2 and onset potential of 0.91 V (vs. RHE). Moreover, CuCo@NCNTs nanocomposite exhibits obvious antibacterial activity, and inhibiting the biofilm on cathode surface in antibacterial test and biomass quantification. The maximum power density (2757 mW m−3) of MFC modified with CuCo@NCNTs is even higher than Pt/C catalyst (2313 mW m−3). In short, CuCo@NCNTs nanocomposite can be an alternative cathode catalyst for MFC. Image 1 • Carbon nanotubes grew in situ on carbon precursors. • Abundant active nitrogen components and bimetal active sites. • High catalytic activity and inhibition of biofilm formation. • As cathode catalyst applied to the air-microbial fuel cell. [ABSTRACT FROM AUTHOR]