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Fe, N co-doped carbon electrocatalyst is one of the most attractive alternatives to Pt/C catalysts due to its high catalytic activity, excellent stability and low cost. However, obtaining stable and efficient Fe, N co-doped carbon oxygen reduction reaction (ORR) catalysts based on simple processes is still a challenge. Herein, Fe, N co-doped porous carbon (Fe–N–C) with an open macroporous frame structure is prepared by using inorganic molten salts (FeCl3·6H2O and ZnCl2) and ethylenediaminetetraacetic acid as the template and nitrogen-containing carbon precursor, respectively. The open pore structure of the Fe–N–C material precisely tailored with the inorganic molten salt template exhibits high specific surface area (676.5 m2 g−1) and appropriate pore size, which can promote oxygen adsorption and expand the oxygen reduction interface, resulting in the acceleration of the electron/charge transfer processes and an improved electrocatalytic performance. The optimized Fe3–N–C-800 electrocatalyst exhibits good catalytic activity for ORR, such as high onset potential of 0.998 V and half wave potential of 0.84 V in alkaline media, as well as high stability and methanol tolerance. Furthermore, a novel Zn–air battery assembled with carbon paper containing Fe3–N–C-800 electrocatalyst as air cathode shows high open-circuit voltage (1.485 V), high specific capacity (870 mA h g−1 at 10 mA cm−2), excellent reversibility and stability. The proposed synthetic strategy provides new opportunities to design and construct carbon frame materials with the desired open macroporous structure to improve their electrocatalytic performance. [ABSTRACT FROM AUTHOR]

The development of efficient and stable non-precious-metal-based electrocatalysts is essential for practical water splitting applications. The electrolysis of water for hydrogen production is a green and efficient method, while urea electrolysis can improve energy conversion efficiency. In this paper, W–Ni3S2/NiS catalysts with heterogeneous structures were synthesized via a one-step hydrothermal method using a W-doping-induced phase transition strategy. The doping of W modulates the morphology of the catalyst, which can form uniform nanorod arrays and improve the activity of the electrocatalyst. In an alkaline solution of 1 M KOH and 0.5 M urea, W–Ni3S2/NiS requires a potential of only 1.309 V to achieve a current density of 10 mA cm−2. An electrolyzer containing urea with W–Ni3S2/NiS as both the cathode and anode can drive a current density of 10 mA cm−2 with a potential of only 1.569 V and has relatively good stability after testing for 20 h. Experimental results show that the improvement in the catalytic activity is due to the rapid charge transfer, exposure of more active sites and better conductivity. Density functional theory calculations show that the W–Ni3S2 material exhibits higher urea adsorption energy, indicating that urea is preferentially adsorbed on its surface. The NiS material shows more state density near the Fermi level, indicating that the introduction of this material enhances the conductivity of the W–Ni3S2/NiS material. The synergistic catalysis of the two materials promoted the improvement of the catalytic activity. This work provides new ideas for the development of highly efficient and stable catalysts by means of doping and interface construction. [ABSTRACT FROM AUTHOR]

Liquid phase oxidation of 2-methylnaphthalene (2-MN) is a common synthetic route for the preparation of 2-methyl-1,4-naphthoquinone (2-MNQ). Metal-free carbon materials doped with heteroatoms have been proven to have excellent catalytic potential in various reaction fields. In this paper, the catalytic performance of N, F co-doped benzoxazine carbon materials for the selective oxidation of 2-MN was studied. The results show that the catalyst obtained at a carbonization temperature of 700 °C has the best catalytic performance. Under optimized conditions, the 2-MN conversion is 97.9%, and the 2-methyl-1,4-naphthoquinone selectivity is 84.3%. In addition, this catalyst still exhibits good catalytic activity after five cycles. Based on the experimental and characterization results, graphitic nitrogen species play a key role in the catalytic reaction and there is an almost linear relationship between the F content and the selectivity of 2-MNQ. This work provides a greener and more efficient method for the preparation of 2-MNQ with N/F co-doped mesoporous carbon. [ABSTRACT FROM AUTHOR]

In 2011, Zhang's research team, in cooperation with Li and Liu, reported the Pt1/FeOx atomically dispersed catalysts for the first time in the world, and based on this, proposed the concept of "single-atom catalysts". Single-atom catalysts (SACs) have a wide range of industrial application prospects in the catalytic synthesis of fine chemicals due to their high atomic utilization rate and special catalytic activity. With the deepening of the research, the preparation methods of SACs emerge in an endless stream, but it is still an urgent problem to realize the industrial production of highly stable SACs prepared in small batches (gram level) or even in large batches (kilogram level). In this review paper, several typical solvent-free green synthetic strategies (e.g., ball milling, physical mixing, gas migration, and pyrolyzing coordination polymers (including MOFs)) for the batch preparation of SACs are introduced. And typical catalytic application of SACs in green synthesis of fine chemicals by means of oxidation reaction, hydrogenation reaction, coupling reaction and other reactions are also introduced. This is the first review paper focusing on the mass preparation techniques of SACs and their applications in fine chemicals production. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) is a new type of renewable energy that can meet people's growing energy needs and is environmentally friendly. In order to improve the industrial application prospects and electrochemical performance of hydrogen evolution catalysts, extensive research on transition metal materials has been carried out. Among the many catalytic materials, cobalt is an element with potential for the hydrogen evolution reaction (HER) due to its abundant reserves, low cost, and small energy barrier for H adsorption. This review classifies the latest research on cobalt-based catalysts according to the types of compound, including cobalt-based sulfides, phosphides, carbides, borides, oxides, etc., and summarizes the latest research progress of cobalt-based compound catalysts in acidic and alkaline media. Strategies to tune the properties of cobalt-based compound catalysts for high catalytic activity for HER are focused on, including structural engineering, defect engineering, and doping, etc. The advantages and limitations of each modified approach are reviewed. Not only that, but also the catalytic activity and advantages of the catalyst are evaluated by using density functional theory (DFT) calculation-related descriptors, activity evaluation parameters, etc. Finally, limitations and challenges of cobalt-based materials for HER are presented, as well as prospects for future research. This paper aims to understand the chemical and physical factors that affect cobalt-based catalysts, and to find directions for future research on cobalt-based catalysts. [ABSTRACT FROM AUTHOR]

Exploring active catalyst components is very important to develop high-performance and highly stable ORR electrocatalysts to replace costly Pt-based catalysts, though it remains an ongoing challenge. In this paper, three ORR catalysts with different active components were obtained by calcination of different proportions of mixed precursors simply and delicately. Among them, precursor 1 (bimetallic polymer Fe/Zn-ZIFs@ZnCO3) played the role of a self-sacrificing template, while precursor 2 (an N, P-co-doped polymer) played the role of a volatile atmosphere. Precursor 2 also embedded N and P heteroatoms into the carbon framework during high-temperature volatilization, which resulted in subtle changes in the active catalyst components. Finally, a hybrid of metal Fe and α-Fe2O3 nanoparticles embedded in N, P-codoped carbon nanotubes with many separated gullies (named α-Fe2O3/Fe@NPC) exhibited excellent ORR catalytic activity in an alkaline solution as compared to commercial Pt/C. This work provides a new strategy for designing controllable active components using volatile precursors. [ABSTRACT FROM AUTHOR]

In this paper, a Co--Fe LDO catalyst was prepared by combining K2Cr2O7 and Cr(NO3)3 to modify the LDH precursor. The catalytic activity of NOx and o-DCB was systematically studied, and the effect of gas composition on the catalytic activity was investigated. The prepared Cr (0.25)/Co--Fe LDO catalyst showed the best catalytic performance, with conversion efficiencies of NOx and o-DCB of 89.0% and 81.6% at 250 °C, respectively. The catalysts were characterized by XRD, BET, SEM, XPS, H2-TPD and NH3-TPD to explore the reaction activity. In addition, the interaction between NH3-SCR and o-DCB oxidation was investigated by changing the gas atmosphere. The results showed that the inhibition at low temperature (< 200 °C) could be attributed to the residues of the by-products of incomplete oxidation. The further oxidation of NO to NO2, and the dissociation of NH3 are the reasons for the mutual promotion of the two reactions in the middle and high temperature sections. Water vapor has little effect on the reaction and the introduction of SO2 will cause irreversible inactivation of the catalyst. [ABSTRACT FROM AUTHOR]

Precious metal nanoparticles (NPs) are attractive for use in the field of catalysis because of their precisely controlled sizes and shapes. However, NPs exhibit insufficient anti-sintering properties under common operating conditions due to their poor thermal stability at elevated temperatures. In this paper, the preparation of noble metallic NPs (Pd and Au) incorporated inside the pores of an SBA-15 support via a sol-immobilization method, which prevents their aggregation, is reported. The Pd NPs retain their size of ∼5 nm within the channels of SBA-15, even after aging at 800 °C for three days under an air atmosphere. However, Au NPs aggregated at a temperature of calcination above 500 °C. Using a set of characterization methods comprising XRD, STEM, HRTEM, TPR, and DRIFTS analysis, it is revealed that Pd on SBA-15 exhibits better anti-sintering properties than the Au supported system. The catalytic activity and durability of M/SBA-15 (M: Pd or Au) catalysts were studied using CO oxidation with and without steam (10 vol%). Interestingly, a hydrothermally treated (Pd/SBA-15-750-H2O-3d) catalyst leads to the partial re-dispersion of Pd. This helps to attain smaller particles of ∼1.6 nm, which play a prominent role in the catalytic performance. This work provides insight into the design of sintering-resistant metal catalysts, which would be suitable for industrial applications under harsh conditions. [ABSTRACT FROM AUTHOR]

In this paper, the effect of the hierarchical arrangement of nanocrystallites on CO oxidation and soot combustion activity has been investigated. Hierarchically structured star-shaped particles (HS stars) were compared with microemulsion-derived, loosely arranged nanoparticles (NPs). Star-like Ce0.9REE0.1O1.95 mixed oxides were synthesized by oxidative thermolysis of Ce0.9REE0.1(HCOO)3 mixed formates. The study of the synthesis, structure and catalytic activity of the porous, star-like ceria-based mixed oxides was presented for the first time. It was shown that each level of the hierarchical structure of the star-like mixed oxides has its own functionality and it is vulnerable to modifications. In-depth characterization of as-synthesized ceria allowed determination of the relationship between the hierarchically structured nature of the material and its catalytic activity in CO oxidation and soot combustion. It was concluded that the presence of the 3D structure composed of ceria nanocrystals significantly improves the stability and catalytic activity of the star-like material in comparison to the nanopowder. Moreover, introduction of the trivalent RE ion into the ceria structure led to further improvement of the CO oxidation performance. Finally, the key–lock catalysis concept was applied to explain the enhanced activity of the hierarchically structured star-shaped ceria particles as a catalyst in the soot combustion process in comparison to nanocrystalline CeO2. [ABSTRACT FROM AUTHOR]

A Cu-based bimetallic hollow structure can be effectively used to enhance the selective oxidation and electrocatalytic activity of a catalyst and to reduce its cost. In this paper, we developed a facile and scalable method for the construction of CuAu bimetallic hollow particles from Cu2O nanoparticle aggregates (NPAs). The synthetic process includes Au growth on the Cu2O NPA surface and silica encapsulation, which is followed by polyol reduction of Cu2O, calcination in air and etching of the SiO2 layer. The obtained hollow CuAu NPs (average diameter of 540 nm and wall thickness of 60 nm) outperform hollow Cu NPs in terms of catalytic activity in the reduction of 4-nitrophenol by NaBH4 in aqueous solution. The activity factors (K = 354 and 255 s−1 g−1) are 2.4 and 1.7 times larger than that of the hollow Cu catalyst, depending on the Au content in the CuAu particles. In addition, the prepared catalyst was stable in the reaction system and can be recycled via centrifugation without a significant loss of catalytic activity. [ABSTRACT FROM AUTHOR]

This paper reports on a binuclear Co(II)Pc which exhibits a previously unknown extremely high catalytic activity for the oxidation of a thiol to the corresponding disulfide. The high activity is explained by an electronic contact between the two Co centres in the complex. [ABSTRACT FROM AUTHOR]

Cobalt has been extensively studied as an effective catalyst for the electrooxidation of sodium borohydride. However, there is still the problem of the low catalytic activity of cobalt catalysts. The improvement in the catalytic activity of cobalt for the electrooxidation of sodium borohydride has become a challenge. In this paper, a novel catalyst Co–P alloy was supported on a copper foam (CF) substrate by a one-step electrodeposition method. In the electrodeposition process, a Co–P/CF electrode with a three-dimensional (3D) porous structure was successfully prepared using hydrogen bubbles as a dynamic template. Through the physical characterization of Co–P/CF, it was proven that the doping of P element produced more Co clusters on the surface of the electrode, which resulted in more active sites. These characteristics were very beneficial for NaBH4 electrooxidation. The electrochemical characterization confirmed that the electrocatalytic activity of Co–P/CF for NaBH4 was better than that of Co/CF. At room temperature, for the Co–P/CF in 2.0 mol dm−3 NaOH + 0.20 mol dm−3 NaBH4 solution, the oxidation current density reached 1795 mA cm−2 at −0.20 V (vs. Ag/AgCl), which was higher than that previously reported the literature. [ABSTRACT FROM AUTHOR]

Homogenization of heterogeneous catalysts is a valuable and interesting research topic. Porous polypyridine-oxadiazole (PPO), as not only a carrier but also a ligand, was designed and synthesized from pyridine-oxadiazole and 1-iodo-4-vinylbenzene. Iridium was anchored onto the skeleton of this polymer (ligand) through coordination bonds. This porous polypyridine-oxadiazole iridium catalyst (PPO-Ir) was clearly characterized by XRD, BET, EDS, HRTEM, SEM, and XPS, and revealed high catalytic activity for the reaction of dimethyl-6-aminouracil with benzyl alcohols, 1,3-dimethylbarbituric acid with benzyl alcohols and 2-aminobenzylamine and benzyl alcohols through dehydrogenation and the borrowing hydrogen strategy with alcohol or water as the solvent. In addition, this PPO-Ir catalyst could be recycled and reused without a manifest loss of catalytic activity for at least five times and revealed potential application value. The mechanism explorations were further conducted to clarify this PPO-Ir and these transformations. [ABSTRACT FROM AUTHOR]

Lignin nanosizing has received much interest as it offers new potential for value-added applications of the currently under-utilized lignin biopolymers. However, conventional lignin nanosizing technologies often rely on the use of large amounts of toxic organic solvents, and a time-consuming dialysis process that is required to remove the solvents. Herein, we present a novel and effective approach using a binary system consisting of green γ-valerolactone (GVL) and glycerol solvents to prepare lignin nanospheres (LNS) without lignin modification and additional dialysis processes. The rationale of LNS formation lies in the emulsification of uniform lignin-containing GVL droplets in glycerol by a process consisting of (1) heating to 80 °C, and (2) cooling to room temperature. Through this simple process, we obtained very high LNS yield (over 90%), with narrow size distribution (about 275 nm) by using maple kraft lignin as the raw material. This lignin nanosizing approach is universal when applied to different sources/types of lignins. The as-prepared LNS were further applied as a green reducing agent and carrier for the synthesis of Pd nanoparticles (NPs) in a facile in situ reduction process. Pd@LNS exhibited significantly enhanced catalytic capacity in the hydrogen evolution from formic acid and in the reduction of Cr(VI) to Cr(III) compared with bare Pd NPs. The Pd@LNS catalyst demonstrated high recyclability owing to the good chemical stability of LNS and robust loading of Pd NPs on LNS. Consequently, this work offers a green, universal and effective approach for LNS fabrication and presents a promising application of LNS as metal NP carriers for catalysis purposes. [ABSTRACT FROM AUTHOR]