Metal-containing Catalysts Research Articles

Towards an EPR on a Chip Spectrometer for Monitoring Radiation Damage During X-ray Absorption Spectroscopy

AbstractElectron paramagnetic resonance (EPR) spectroscopy is an essential tool to investigate the effects of ionizing radiation, which is routinely administered for reducing contaminations and waste in food products and cosmetics as well as for sterilization in industry and medicine. In materials research, EPR methods are not only employed as a spectroscopic method of structural investigations, but also have been employed for detection of changes in electronic structure due to radiation damage from high energy X-rays, for example, to monitor radical formation inside biomolecules caused by X-ray irradiation at carbon, nitrogen, and oxygen K-edges at synchrotron facilities. Here a compact EPR spectrometer, based on EPR-on-a-chip (EPRoC) sensor and a portable electromagnet, has been developed as a solution for monitoring radiation damage of samples during their investigation by X-ray absorption spectroscopy (XAS) at synchrotron facilities. A portable electromagnet with a soft iron core and forced air temperature stabilization was constructed as the source of the external magnetic field. The sweep range of magnetic field inside the most homogeneous region of the portable electromagnet is 12–290 mT. The compact spectrometer performance was evaluated by placing the EPRoC sensor inside either a commercial electromagnet or the portable electromagnet to record the EPR spectrum of tempol, irradiated alanine, and dilithium phthalocyanine (Li2Pc). The potential performance of the portable spectrometer for the detection of radiation damage in organic compounds and transition metal-containing catalysts during XAS measurements in both fluorescence and transmission modes was calculated with promising implications for measurements after implementation in a synchrotron-based XAS spectrometer.

Synthesis and Molecular Docking Study of Some New Thiazole-coumarin Molecular Hybrids as Antibacterial Agents.

The emergence of drug-resistant bacteria and multidrug-resistant diseases, both of which are associated with high mortality, has posed a serious global health issue. Thiazoles and coumarins were reported as antimicrobial agents. This research paper aims to describe the synthesis of some novel thiazole derivatives bear-ing a coumarin residue as antibacterial agents Methods: The thiazole - coumarin hybrids were synthesized starting from the condensation of 3-acetyl coumarin (1) hydrazine carbothioamide (2) or thisemicarbazide then reacting the resulting products with different p-substituted phenacyl bromides (4a-e), hydrazonoyl chlorides (8a-e), and (11). In vitro antibacterial activity was studied in this work. In addition, molecular docking studies for the new compounds have also been carried out to investigate the binding mode of actions against the target DNA gyrase B. Some of the newly synthesized compounds such as compounds 10b, 7, and 6b showed pronounced activities against Gram (+ve) and Gram (-ve) bacteria compared to a reference antibacterial agent. Compounds 10b, 7, and 6b exhibited the best binding affinity against the target. We could obtain a series of precious hitherto unknown thiazole derivatives with varied antibacterial activities from cheap laboratory-available starting material following rather simple environmentally friendly techniques avoiding the use of hazardous or heavy metal-containing catalysts.

Highly efficient metal free aldehyde-functionalized indoles for direct glucose fuel cell anode catalyst

In this study, alternative organic catalysts to metal-containing catalysts for glucose electrooxidation were prepared by the Suzuki Miyaura coupling reaction method and characterized by nuclear magnetic resonance (NMR), fourier transform infrared spectroscopy (FT-IR), and liquid chromatography with tandem mass spectrometry (LC-MS-MS). InTA-1, InPA-1, InFA-1, InTA-2, InPA-2, InFA-2, InTA-3, InFA-3, and InPA-3 were obtained with the yield of 74%, 82%, 72%, 70%, 75%, 68%, 60%, 71%, and 85%. Among the synthesized catalysts, the InTA-3 catalyst possesses the highest electrocatalytic activity (3.17 mA cm−2) and long-term stability compared to other organic catalysts. InTA-3 catalyst has the lowest charge transfer resistance toward glucose electrooxidation. It was concluded that as a metal-free catalyst, InTA-3 is a cheap and promising electrocatalyst for direct glucose fuel cell anode.

Preparation of nitrogen-doped carbon pyrolyzed from ZIF-8 and its performance in electrocatalytic oxygen reduction to hydrogen peroxide

As an environment-friendly strategy, electrocatalytic hydrogen peroxide (H2O2) generation via two-electron oxygen reduction reaction (2e– ORR) has attracted significant scientific and technological attention. Nevertheless, limited to the low catalytic activity and high cost of noble metal-containing catalysts, forging desired electrocatalysts with high catalytic activity, low cost, and sustainability is still challenging. In this work, nitrogen doped porous carbon materials named p-ZIF-800 and p-ZIF-950 were obtained by pyrolysis of zeolitic imidazolate framework-8 (ZIF-8) nanocrystals at 800 °C and 950 °C, respectively. Then, they were employed as a catalytic layer in the gas diffusion electrodes p-ZIF-n/Ni/CB (n = 800 °C or 950 °C, CB = acetylene black). The production rates of H2O2 are up to 1.18 mg h−1 cm−2 and 1.25 mg h−1 cm−2 for p-ZIF-800/Ni/CB and p-ZIF-950/Ni/CB, respectively. Noticeably, although p-ZIF-800 had a lower degree of graphitization the difference in catalytic activity between p-ZIF-800 and p-ZIF-950 is negligible. This can be construed as a higher total nitrogen and richer mesoporous structure in p-ZIF-800 than in p-ZIF-950. Under optimized conditions of an electrode spacing of 3 cm, a pH value of 6.5, and a current density of 7.5 mA cm−2, the H2O2 production rate of p-ZIF-800/Ni/CB in the “floating-cathode” cell is up to as high as 2.09 mg h−1 cm−2, which is about 3.3 times higher than that of the cell with the “submerged-cathode” under aeration and stirring. Also, the p-ZIF-800/Ni/CB cathode demonstrates remarkable stability, it maintains its structure without losing catalytic activity after 5 catalytic cycle experiments. These results indicate that the state-of-the-art pyrolysis-based nitrogen-doped porous carbon materials exhibit a high potential for the advanced electrocatalyst of H2O2 electrogeneration.

Activated carbon from waste fabrics as a catalyst for NaBH4 methanolysis

Hydrogen energy is attractive as a sustainable and clean energy. Chemical hydrides are being studied as a solution to the transportation and storage problems of hydrogen. Hydrogen can be produced by methanolysis reaction of sodium borohydride on a suitable catalyst. For this purpose, metal catalysts with high catalytic activity are generally used. Despite their high catalytic activity, the environmental impact and cost of metal-containing catalysts has led to increased interest in synthesizing metal-free catalysts. Activated carbons are advantageous materials for metal-free catalyst applications. In recent years, industrial wastes have attracted much attention for the synthesis of sustainable materials for activated carbon preparation. In this study, activated carbons are produced from waste fabrics by chemical activation method using H3PO4 and KOH chemical agents at different impregnation ratios (1:1, 2:1 and 3:1 % w:w) and different carbonization temperatures (400, 500, 600°C for H3PO4 and 600, 700, 800°C for KOH). These carbons are used as catalysts for hydrogen production and their catalytic activity is evaluated based on hydrogen generation rate (HGR). Therefore, the effect of different conditions used in the preparation of activated carbon was investigated to determine its impact on HGR. The increase in carbonization temperature decreases the HGR value of the catalyst. The increase in acid concentration increases the HGR value. The highest HGR value is obtained as 39600 mL/(min.gcat) with YKK1–800 activated carbon. Once the carbon with high activity is identified, the effect of reaction conditions such as NaBH4, methanol, catalyst amount, and temperature on HGR is investigated. The catalytic activities of the prepared activated carbons in NaBH4 electrooxidation are also investigated. YKK3–700 activated carbon shows the highest catalytic activity at 1.91 mA/cm2 at −0.63 V peak potential. This result is promising for the use of metal-free catalysts for direct sodium borohydride fuel cells.

Modern Trends in the Synthesis of Disulfides: From Metal-Containing Catalysts to Nonmaterial Reagents (Review)

Modern Trends in the Synthesis of Disulfides: From Metal-Containing Catalysts to Nonmaterial Reagents (Review)

Promoting Bifunctional Oxygen Catalyst Activity of Double-Perovskite-Type Cubic Nanocrystallites for Aqueous and Quasi-Solid-State Rechargeable Zinc-Air Batteries

Transition metal oxide materials are promising oxygen catalysts that are alternatives to expensive and precious metal-containing catalysts. Integration of transition metal oxides with high activity for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is an important pathway for good bifunctionality. In contrast to the conventional physical mixing and hybridization strategies, perovskite-type oxide provides an ideal structure for the integration of the transition metal element atoms on an atomic scale. Herein, B-site ordered double-perovskite-type La1.6Sr0.4MnCoO6 nanocrystallites with ultra-small cubic (20–50 nm) morphology and high specific surface areas (25 m2 g−1) were proposed. Rational designs were integrated to promote the ORR-OER catalysis, e.g., introducing oxygen vacancies via A-site cation substitution, further increasing surface oxygen vacancies via integration of a small amount of Pt/C and nanosizing of the material via a facile molten-salt method. The batteries with the La1.6Sr0.4MnCoO6 nanocrystallites and an aqueous alkaline electrolyte demonstrate decent discharge−charge voltage gaps of 0.75 and 1.10 V at 1 and 30 mA cm−2, respectively, and good cycling stability of 250 h (1500 cycles). A coin-type battery with a gel−polymer electrolyte also presents a good performance.

Mesoporous tubular g-C3N4 as an efficient metal-free photocatalyst with peroxymonosulfate to degrade carbamazepine

In advanced oxidation processes with metal-containing catalysts, metal dissolution usually leads to reduced efficiency and biotoxicity. Therefore, it is very important to find efficient non-metallic materials. In this work, a metal-free mesoporous tubular g-C3N4 was fabricated using melamine and urea mixed according to the mass ratios of 1:12 (TPCN12) by a facile one-step thermal polymerization method. Mesoporous tubular TPCN12 was proved to be successfully synthesized by scanning electron microscope (SEM) and X-ray diffraction (XRD). Then the degradation of carbamazepine (CBZ) by activating peroxymonosulfate (PMS) of TPCN12 under visible light was investigated. It was found that degradation rate constant of CBZ in TPCN12/Vis/PMS system (0.0939 min−1) exhibited great superiority over that in TPCN12/Vis system (0.0149 min−1) and in TPCN12/PMS system, which indicated TPCN12, Vis and PMS had a synergistic effect. The dominant role of the electron transfer and the primary contribution of the holes (h+) and •O2− reactive species were revealed in TPCN12/Vis/ PMS system. Furthermore, the system showed sufficient advantages over a wide pH range and high resistance to inorganic anions. In general, the TPCN12/Vis/PMS system was capable of high stability and recyclability. This metal-free mesoporous tubular catalyst was proposed to achieve efficient and green elimination of pharmaceutical organic pollutants.

Facilitating two-electron oxygen reduction with pyrrolic nitrogen sites for electrochemical hydrogen peroxide production

Electrocatalytic hydrogen peroxide (H2O2) production via the two-electron oxygen reduction reaction is a promising alternative to the energy-intensive and high-pollution anthraquinone oxidation process. However, developing advanced electrocatalysts with high H2O2 yield, selectivity, and durability is still challenging, because of the limited quantity and easy passivation of active sites on typical metal-containing catalysts, especially for the state-of-the-art single-atom ones. To address this, we report a graphene/mesoporous carbon composite for high-rate and high-efficiency 2e− oxygen reduction catalysis. The coordination of pyrrolic-N sites -modulates the adsorption configuration of the *OOH species to provide a kinetically favorable pathway for H2O2 production. Consequently, the H2O2 yield approaches 30 mol g−1 h−1 with a Faradaic efficiency of 80% and excellent durability, yielding a high H2O2 concentration of 7.2 g L−1. This strategy of manipulating the adsorption configuration of reactants with multiple non-metal active sites provides a strategy to design efficient and durable metal-free electrocatalyst for 2e− oxygen reduction.

Hyper-crosslinked polymer derived porous Co@CN catalyst for selective hydrogenation of quinoline

A benzotrizole-based hyper-crosslinked polymer (HCP) was employed to load cobalt and prepare a novel metal-containing nitrogen-doped carbon catalyst for the selective hydrogenation of quinoline. The high porosity, large surface area and nitrogen-containing monomer of HCP made a positive contribution to metal loading. Owing to the excellent thermostability of HCP, the original porous texture of HCP was partially reserved during pyrolysis, which resulted in highly dispersive Co species in the N-doped carbon material. The remaining mesopores in Co@CN catalyst during thermal decomposition provided available diffusion channels for substrates, which facilitated their full contact with catalytic active sites and their effective conversion. The prepared Co@CN catalyst achieved a conversion rate of 100% and a selectivity of 100% in the hydrogenation of quinoline into 1, 2, 3, 4-tetra-hydroquinoline in water at 100 °C under 3 MPa H2. The as-synthesized catalyst had good reuse performance, exhibiting >95% conversion rate and >99% selectivity even after 12 cycles. Moreover, the catalyst could also be applied to the selective hydrogenation of a serial of quinoline derivatives. The study provided a useful strategy for constructing metal-doped carbon materials which might be applicable for other metals and other reactions.

Structural and biochemical elucidation of class I hybrid cluster protein natively extracted from a marine methanogenic archaeon.

Whilst widespread in the microbial world, the hybrid cluster protein (HCP) has been paradoxically a long-time riddle for microbiologists. During three decades, numerous studies on a few model organisms unravelled its structure and dissected its metal-containing catalyst, but the physiological function of the enzyme remained elusive. Recent studies on bacteria point towards a nitric oxide reductase activity involved in resistance during nitrate and nitrite reduction as well as host infection. In this study, we isolated and characterised a naturally highly produced HCP class I from a marine methanogenic archaeon grown on ammonia. The crystal structures of the enzyme in a reduced and partially oxidised state, obtained at a resolution of 1.45 and 1.36-Å, respectively, offered a precise picture of the archaeal enzyme intimacy. There are striking similarities with the well-studied enzymes from Desulfovibrio species regarding sequence, kinetic parameters, structure, catalyst conformations, and internal channelling systems. The close phylogenetic relationship between the enzymes from Methanococcales and many Bacteria corroborates this similarity. Indeed, Methanococcales HCPs are closer to these bacterial homologues than to any other archaeal enzymes. The relatively high constitutive production of HCP in M. thermolithotrophicus, in the absence of a notable nitric oxide source, questions the physiological function of the enzyme in these ancient anaerobes.

Alcohol imination catalyzed by carbon nanostructures synthesized by C(sp2)-C(sp3) free radical coupling

Imines are important intermediates for synthesizing various fine chemicals, with the disadvantage of requiring the use of expensive metal-containing catalysts. We report that the dehydrogenative cross-coupling of phenylmethanol and benzylamine (or aniline) directly forms the corresponding imine with a yield of up to 98%, and water as the sole by-product, in the presence of a stoichiometric base, using carbon nanostructures as the "green" metal-free carbon catalysts with high spin concentrations, which is synthesized by C(sp2)-C(sp3) free radical coupling reactions. The catalytic mechanism is attributed to the unpaired electrons of carbon catalysts to reduce O2 to O2·-, which triggers the oxidative coupling reaction to form imines, whereas the holes in the carbon catalysts receive electrons from the amine to restore the spin states. This is supported by density functional theory calculations. This work will open up an avenue for synthesizing carbon catalysts and offer great potential for industrial applications.

Pyrolysis-gasification of biomass and Municipal Plastic Waste using transition metal modified catalyst to investigate the effect of contaminants

Pyrolysis and gasification are one of the possible solutions for the recycling of polymer waste. This work focussing to the combined pyrolysis-gasification of different wastes to investigate the effect of raw materials, temperature, and contaminants. To enhance the pyrolysis reactions different transition metal-containing catalysts were used: Ni/ZSM-5, Ce/Ni/ZSM-5, La/Ni/ZSM-5, Ce/La/ZSM-5. Different sourced biomasses, municipal plastic wastes and municipal solid waste had been used as raw materials with different amount of contaminants. Regarding biomass, the effect of nitrogen and sulphur were investigated to the product yields and composition, while that nitrogen and chlorine in case municipal plastic waste. The pyrolysis-gasification experiments had been performed in a two zones batch reactor in horizontal layout, where 500 °C were used in the pyrolysis step, while the gasification reactions were investigated at 500 and 800 °C in the presence of steam. The composition of gases were measured by GC-FID and GC-TCD, while that of the hydrocarbon oils by GC-FID and HPLC. It was found, that the raw material significantly affected the product yields; e.g. in addition hydrocarbon products, aqueous products found only in case of biomass and municipal solid waste, while municipal plastic waste pyrolysis-gasification resulted hydrocarbon gases, hydrocarbon oil and solid char. Significant amount of carbon monoxide and carbon dioxide can be obtained in case, when raw materials contained cellulose, hemicellulose or lignin in their main structure, however, the concentration of carbon monoxide can be increase at 800 °C in case of municipal plastic waste. The highest syngas yield can be found in case of plastic waste. The ratio of hydrogen/carbon monoxide, that of carbon bon monoxide and carbon dioxide and the structure of aromatic hydrocarbons can be also significantly affected by the raw materials and the contaminants.

Efficient electrochemical NO reduction to NH3 over metal-free g-C3N4 nanosheets and the role of interface microenvironment

The ever-increasing NO emission has caused severe environmental issues and adverse effects on human health. Electrocatalytic reduction is regarded as a win-win technology for NO treatment with value-added NH3 generation, but the process is mainly relied on the metal-containing electrocatalysts. Here, we developed metal-free g-C3N4 nanosheets (deposited on carbon paper, named as CNNS/CP) for NH3 synthesis from electrochemical NO reduction under ambient condition. The CNNS/CP electrode afforded excellent NH3 yield rate of 15.1 μmol h−1 cm−2 (2180.1 mg gcat−1 h−1) and Faradic efficiency (FE) of ∼41.5 % at − 0.8 and − 0.6 VRHE, respectively, which were superior to the block g-C3N4 particles and comparable to the most of metal-containing catalysts. Moreover, through adjusting the interface microenvironment of CNNS/CP electrode by hydrophobic treatment, the abundant gas-liquid-solid triphasic interface improved NO mass transfer and availability, which enhanced NH3 production and FE to about 30.7 μmol h−1 cm−2 (4424.2 mg gcat−1 h−1) and 45.6 % at potential of − 0.8 VRHE. This study opens a novel pathway to develop efficient metal-free electrocatalysts for NO electroreduction and highlights the importance of electrode interface microenvironment in electrocatalysis.

Greener and scalable mechanosynthesis of bis(3-indolyl)methane as an example of versatile pharmaceutical scaffold: Is the mechanochemical technique a metal-free process?

The metal-free feature of mechanosynthesis of bis(3-indolyl)methane derivatives using poly(4-vinyl pyridine), a commercially available functional polymer, by ball mill technique at ambient conditions was studied. The condensation of various carbonyl compounds with two indoles smoothly proceeded, and pure products were easily isolated in high to excellent yields. Poly(4-vinylpyridine) exhibited high recyclability without any loss of catalytic activity or change in the chemical structure. The influence of polymer M̅W with a certain PDI on the mechanosynthesis of BIMs was investigated. In addition, the effect of the ball and jar with zirconium oxide material was studied on the rate and yield of the BIMs synthesis process. The method was scalable and generated minimal hazardous wastes. Some merits of the current methodology are such as the good to high yields for various carbonyl compounds and avoiding the use of toxic, expensive, and metal-containing catalysts with a tedious process of preparation, separation, and purification.

Bromide-Mediated Photoelectrochemical Epoxidation of Alkenes Using Water as an Oxygen Source with Conversion Efficiency and Selectivity up to 100.

In a photoelectrochemical (PEC) cell, the production of solar fuels such as hydrogen is often accompanied either by the oxidation of water or by the oxidation of organic substrates. In this study, we report bromide-mediated PEC oxidation of alkenes at a mesoporous BiVO4 photoanode and simultaneous hydrogen evolution at the cathode using water as an oxygen source. NaBr as a redox mediator was demonstrated to play a dual role in the PEC organic synthesis, which facilitates the selective oxidation of alkenes into epoxides and suppresses the photocorrosion of BiVO4 in water. This method enables a near-quantitative yield and 100% selectivity for the conversion of water-soluble alkenes into their epoxides in H2O/CH3CN solution (v/v, 4/1) under simulated sunlight without the use of noble metal-containing catalysts or toxic oxidants. The maximum solar-to-electricity efficiency of 0.58% was obtained at 0.39 V vs Ag/AgCl. The obtained epoxide products such as glycidol are important building blocks of the chemical industry. Our results provide an energy-saving and environment-benign approach for producing value-added chemicals coupled with solar fuel generation.

Kinetic evaluation of perovskites-type catalysts in the reduction of 4-nitrophenol: A mechanistic elucidation study

• The effect of electron scavengers helps determine the type of surface mechanism in 4NP reduction. • 4NP reduction by borohydride is a surface catalytically driven reaction. • Perovskites, are alternatives to noble metal-containing heterogeneous catalysts for degradation of environmental pollutants. Herein, we report on the catalytic activity of ABO 3 perovskites (A = La or Sr, B = Co, Sn, Fe, or Al) synthesized by nanocasting technique with silica-based KIT-6 as a hard template. The physical and chemical characteristics of the perovskites were determined using various techniques such as powder X-ray diffraction, nitrogen sorption, transmission and scanning electron microscopes and temperature programmed desorption. The synthesized ABO 3 perovskites were used as heterogeneous catalysts in the reduction of 4-nitrophenol (4NP) by sodium borohydride (NaBH 4 ) to 4-aminophenol (4AP). The perovskites exhibit surface areas ranging from 19 to 101 m 2 /g. Among the as-synthesized perovskites SnAlO 3 was the most acidic catalyst and exhibited the highest catalytic activity towards 4NP reduction. We further explored the role of electron scavengers in elucidating the catalytic mechanism and postulate that the reduction of 4NP follows a surface-driven electron transfer mechanism.

SYNTHESIS OF THIAZOLOQUINAZOLINARYLTELLURID

Symmetric and asymmetric chalcogenides of organic nature are a class of organometallic compounds that are widely used as intermediates in a number of organic reactions, as ligands in the chemistry of coordination compounds, they have a wide range of biological activity. Diaryl tellurides, which are important for the formation of new carbon-carbon bonds, have a special area in the chemistry of organotelluric compounds. The synthesis of new representatives of this class of tellurium-containing compounds is an urgent task.
 One of the main methods of obtaining of diaryl tellurides is the interaction of arylboronic acids with diarylditellurides in the presence of various metal-containing catalysts or microwave radiation. In this paper, we have considered the method of obtaining asymmetric tellurides by the reaction of reduction of sodium sulfite with salts of thiazoloquinazolinaryl dichlorotellurides without the usage of catalysts.
 It was found that the reaction of 2-((dichloro(4-methoxyphenyl)-4-tellanyl)methyl)-2,3-dihydro-5H-thiazolo[2,3-b]quinazolin-5-one hydrochloride with triple excess of sodium sulfite leads to the formation of 2-((4-methoxyphenyl)tellanyl)methyl)-2,3-dihydro-5H-thiazolo [2,3-b]quinazolin-5-one. It should be noted that the recovery does not break the bond Te-C. In the analysis of spectral data, the signals of the protons of the thiazole cycle and the exocyclic aryltelluric fragment undergo a strong field shift.
 Thus, as a result of the reduction reaction of 2-((dichloro(4-methoxyphenyl)-4-tellanyl)methyl)-2,3-dihydro-5H-thiazolo[2,3-b]quinazolin-5-one hydrochloride, a biologically promising and suitable for further functionalization telluride was received.

Defects engineering of metal-organic framework immobilized Ni-La(OH)3 nanoparticles for enhanced hydrogen production

The development of low-cost, efficient, and durable catalysts to boost hydrogen production from hydrous hydrazine (N2H4·H2O) and hydrazine borane (N2H4BH3) is critical, but still a huge challenge. Herein, for the first time, noble-metal-free La(OH)3-doped Ni nanoparticles (NPs) supported on defect-rich metal−organic framework were constructed via a facile, green, and low-cost wet-chemical method. It is first found that the number of defects in MIL-125(Ti) can be easily regulated by a simple but efficient method. As a result, the defect-rich MIL-125-supported Ni-La(OH)3 catalyst shows superior catalytic activity, 100 % H2 selectivity, and robust durability for N2H4·H2O dehydrogenation with NaOH at 343 K, providing a turnover frequency (TOF) value high up to 870 h−1, surpassing all the non-noble metal catalysts reported so far and even outperforming some noble metal-containing catalysts. Interestingly, the catalyst also shows excellent catalytic efficiency for hydrogen production from N2H4BH3 with a TOF value as high as 2381 h−1 at 343 K. The superior catalytic efficiency is mainly due to the existence of abundant defective MIL-125, electron-rich, good dispersed and small Ni NPs, as well as the synergistic effect between metal and support. This work delivers inspiration in defect engineering and provides a promising strategy for rationally designing high-efficiency MOFs-based catalysts for hydrogen generation and other heterogeneous catalysis.

Electroreduction of oxygen on iron- and cobalt-containing nitrogen-doped carbon catalysts prepared from the rapeseed press cake

• Nitrogen, Co- and/or Fe-doped nanocarbons prepared from rapeseed press cake. • ORR activity of Fe-containing catalysts is close to that of Pt/C in 0.1 M KOH. • Inhibition of ORR by CN − ions shows the existence of MN x centres. • Catalysts show high methanol tolerance and good stability. • In AEMFC , P max = 131 mW cm −2 achieved with bimetallic catalyst. Transition metal-containing nitrogen-doped carbon catalysts for the electrochemical oxygen reduction reaction (ORR) were prepared from inexpensive biomass - rapeseed press cake; cobalt and/or iron salts and dicyandiamide were employed as metal and nitrogen sources. After acid treatment, the catalysts showed excellent electrocatalytic ORR activity in rotating disk electrode experiments in 0.1 M KOH solution, comparable to that of Pt/C (20 wt%) catalyst; good tolerance to methanol and high stability in short-time tests. The bimetallic catalyst displayed moderate performance as cathode material in anion exchange membrane fuel cell (AEMFC) test, by reaching the peak power density of 131 mW cm −2 .