Developing high-performance non-precious catalysts to replace platinum as oxygen reduction reaction (ORR) catalysts is still a big scientific and technological challenge. Herein, we report a simple method for the synthesis of a FeNC catalyst with a 3D hierarchically micro/meso/macro porous network and high surface area through a simple carbonization method by taking the advantages of a high specific surface area and diverse pore dimensions in 3D porous covalent-organic material. The resulting FeNC-900 electrocatalyst with improved reactant/electrolyte transport and sufficient active site exposure, exhibits outstanding ORR activity with a half-wave potential of 0.878 V, ca. 40 mV more positive than Pt/C for ORR in alkaline solution, and a half-wave potential of 0.72 V, which is comparable to that of Pt/C in acidic solution. In particular, the resulting FeNC-900 exhibits a much higher stability and methanol tolerance than those of Pt/C, which makes it among the best non-precious catalysts ever reported for ORR.

Ultrafine monodisperse bimetallic NiPt nanoparticles with different compositions have been successfully synthesized by coreduction of nickel acetylacetonate and platinum acetylacetonate with borane-tert-butylamine in oleylamine. Among all the catalysts tested, Ni84Pt16/graphene exhibited 100% hydrogen selectivity, and marked high catalytic activity, with TOF values of 415 h–1 at 50 °C, and 133 h–1 at 25 °C for hydrogen generation from alkaline solution of hydrazine.Keywords: hydrazine; hydrogen storage; monodisperse; Ni; Pt

Highly dispersed ultrafine NiIr nanoparticles with different compositions were successfully encapsulated into the cavities of MIL-101 and applied to catalyze the dehydrogenation of hydrazine monohydrate. The catalytic activities relied on the composition of metals, support materials, alkaline, as well as the temperature strongly. Among all the catalysts tested, Ni85Ir15@MIL-101 exhibited the highest catalytic performance in the presence of NaOH at 50 °C. Even at 25 °C, the Ni85Ir15@MIL-101 exhibited the complete dehydrogenation of hydrazine with a turnover frequency value of 24 h–1.Keywords: Hydrazine; Hydrogen storage; Ir; MIL-101; Ni;

•One-step synthesis of graphene supported Rh NPs.•The catalysts exhibit excellent catalytic activity.•The catalysts show good durable stability.Well dispersed 2.4 nm Rh nanoparticles (NPs) supported on graphene have been synthesized via a one-step in situ procedure by using methylamine borane (MeAB) as the reducing agent. Compared with other conventional supports, such as carbon black, SiO2, γ-Al2O3, and the physical mixture of Rh and graphene, the as-prepared Rh NPs supported on graphene exhibit superior catalytic activity towards the hydrolysis of ammonia borane. Kinetic studies of catalytic hydrolysis of amine boranes indicate that the as-synthesized Rh/graphene is first order with respect to Rh concentration. Among all the reported Rh-based catalysts, the Rh/graphene exhibits the highest turnover frequency (TOF) values of 325 and 146 min−1, the lowest activation energy (Ea) values of 19.7 and 16.4 kJ/mol, toward hydrolysis of ammonia borane (AB) and MeAB, respectively.

•Facile synthesis of graphene supported monodisperse Ru NPs.•The catalysts exhibit excellent catalytic activity.•The catalysts show good durable stability.Monodisperse ruthenium (Ru) nanoparticles (NPs) supported on graphene have been synthesized by co-reduction of RuCl3 and graphite oxide in ethylene glycol using ascorbic acid as reducing agents. Thanks to the narrow size distribution of Ru NPs and the synergistic effect with graphene, the as-synthesized Ru/graphene exerts exceedingly high catalytic activity toward hydrogen generation from hydrolysis of ammonia borane, with the turnover frequency (TOF) value of 600 mol H2 min−1 (mol Ru)−1, which is among the highest value ever reported.

•One-step in situ synthesizes Ru@Ni core–shell NPs supported on graphene.•High activity toward the hydrolysis of AB with the TOF value of 340 mol H2.•Efficient and reusable catalyst for hydrolysis of MeAB.Ru@Ni core–shell nanoparticles (NPs) supported on graphene have been synthesized by one-step in situ co-reduction of aqueous solution of ruthenium (III) chloride, nickel (II) chloride, and graphene oxide (GO) with ammonia borane (AB) as the reducing agent under ambient condition. The as-synthesized NPs exhibit much higher catalytic activity for hydrolytic dehydrogenation of AB than the monometallic, bimetallic alloy (RuNi/graphene), and graphene-free core–shell (Ru@Ni) counterparts. Additionally, the Ru@Ni/graphene NPs facilitate the hydrolysis of AB, with the turnover frequency (TOF) value of 340 mol H2 min−1 (mol Ru)−1, which is among the highest value reported on Ru-based NPs so far, and even higher than the reversed Ni@Ru NPs. Furthermore, the as-prepared NPs exert satisfied durable stability and magnetically recyclability for the hydrolytic dehydrogenation of AB and methylamine borane (MeAB). Moreover, this simple synthetic method can be extended to other Ru-based bimetallic core–shell systems for more applications.

•Facile synthesize trimetallic Ag@CoFe and Ag@NiFe core–shell NPs.•The catalysts exhibit excellent catalytic activity toward hydrolysis of AB and MeAB.•The catalysts supported on graphene exhibit the highest activity.We reported the synthesis and characterization of two trimetallic (Ag@CoFe, and Ag@NiFe) core–shell nanoparticles (NPs), and their catalytic activity toward hydrolytic dehydrogenation of ammonia borane (AB) and methylamine borane (MeAB). The as-synthesized trimetallic core–shell NPs were obtained via a facile one-step in situ procedure using methylamine borane as a reducing agent and graphene as the support under ambient condition. The as-synthesized NPs are well dispersed on graphene, and exhibit higher catalytic activity than the catalysts with other conventional supports, such as the SiO2, carbon black, and γ-Al2O3. Additionally, compared with NaBH4 and AB, the as-synthesized Ag@CoFe/graphene NPs reduced by MeAB exhibit the highest catalytic activity, with the turnover frequency (TOF) value of 82.9 (mol H2 min−1 (mol Ag)−1), and the activation energy (Ea) value of 32.79 kJ/mol. Furthermore, the as-prepared NPs exert good durable and magnetically recyclability for the hydrolytic dehydrogenation of AB and MeAB. Moreover, this simple strategic synthesis method can be easily extended to the facile preparation of other graphene supported multi-metal core–shell NPs.

•One-step synthesis of graphene supported CoNi NPs by the mixture of NaBH4/AB.•The TOF is 16.4 mol H2 min−1 (mol catalyst)−1 for hydrolysis of AB.•The second lowest activation energy of 13.49 kJ/mol for hydrolysis of AB.•The catalysts show good durable stability and magnetically recyclability.Well dispersed magnetically recyclable bimetallic CoxNi1−x (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) nanoparticles (NPs) supported on graphene have been synthesized via a facile in situ one-step procedure, using the mixture of sodium borohydride (NaBH4) and methylamine borane (MeAB) as the reducing agent under ambient condition. These NPs were composition dependent for catalytic hydrolysis of amine boranes. Among all the CoNi/graphene catalysts tested, the Co0.9Ni0.1/graphene NPs exhibit the highest catalytic activity toward hydrolysis of AB with the turnover frequency (TOF) value of 16.4 (mol H2 min−1 (mol catalyst)−1), being higher than that of most reported non-noble metal-based NPs, and even many noble metal-based NPs. Moreover, the activation energy (Ea) value is 13.49 kJ/mol, which is the second lowest value ever reported for catalytic hydrolytic dehydrogenation of ammonia borane, indicating the superior catalytic performance of the as-synthesized Co0.9Ni0.1/graphene catalysts. Additionally, Compared with other reducing agents, such as NaBH4, AB, MeAB, and the mixture of NaBH4 and AB, the as-synthesized Co0.9Ni0.1/graphene catalysts reduced by the mixture of NaBH4 and MeAB exert the highest catalytic activity. The Co0.9Ni0.1 NPs supported on graphene exhibit higher catalytic activity than catalysts with other conventional supports, such as SiO2, carbon black, and γ-Al2O3. Furthermore, the as-synthesized Co0.9Ni0.1/graphene NPs show good recyclability and magnetically reusability for the hydrolytic dehydrogenation of amine boranes, which make the practical reusing application of the catalysts more convenient.

•Facile synthesize graphene supported Ag@Co core–shell NPs.•The catalysts exhibit excellent catalytic activity toward hydrolysis of AB and MeAB.•The catalysts show good durable stability and magnetically recyclability.Well-dispersed Ag@Co core–shell nanoparticles (NPs) supported on graphene with controlled compositions were synthesized by the reduction of silver nitrate, cobalt(II) acetate, and graphene oxide (GO) in the presence of hydrazine and ethylene glycol. These NPs were composition dependent catalysts for hydrogen generation from the hydrolysis of ammonia borane. Among all Ag@Co catalysts tested, the Ag0.5@Co0.5/graphene NPs exhibited the highest catalytic activity, with the turnover frequency (TOF) value of 10.5 mol H2 min−1 (mol catalyst)−1, and activation energy value of 39.33 kJ/mol. Kinetic studies reveal that the catalytic hydrolysis of AB and MeAB are both first order with respect to the catalyst concentrations. Furthermore, the Ag0.5@Co0.5/graphene NPs show good durable stability and magnetically recyclability for the hydrolytic dehydrogenation of AB and MeAB, which makes the practical recycling application of the catalyst more convenient.

Urea can improve the solubility and stability of cellulose in aqueous alkali solution, while its role has not come to a conclusion. To reveal the role of urea in solution, NMR was introduced to investigate the interaction between urea and the other components in solution. Results from chemical shifts and longitudinal relaxation times show that: (1) urea has no strong direct interaction with cellulose as well as NaOH; (2) urea does not have much influence on the structural dynamics of water. Urea may play its role through van der Waals force. It may accumulate on the cellulose hydrophobic region to prevent dissolved cellulose molecules from re-gathering. The driving force for the self-assembly of cellulose and urea molecules might be hydrophobic interaction. In the process of cellulose dissolution, OH− breaks the hydrogen bonds, Na+ hydrations stabilize the hydrophilic hydroxyl groups and urea stabilizes the hydrophobic part of cellulose.

Well dispersed magnetically recyclable trimetallic core–shell Ag@CoNi nanoparticles (NPs) supported on graphene have been synthesized via a facile one-step in situ procedure using methylamine borane (MeAB) as the reducing agent. The as-synthesized NPs exhibit much higher catalytic activities for hydrolytic dehydrogenation of ammonia borane (AB) than the monometallic, bimetallic, trimetallic alloy (AgCoNi/graphene), and graphene free (Ag@CoNi) counterparts. Moreover, compared with NaBH4 and AB, the weaker reducing agent MeAB has much better control during the synthesis of the graphene supported Ag@CoNi NPs, which resulted in the highest catalytic activity. Kinetic studies indicate that the catalytic hydrolysis of AB by the Ag@CoNi/graphene NPs is first order, with the activation energy measured to be 36.15 kJ mol−1. Furthermore, the as-prepared NPs exert good catalytic activities and recycle stabilities towards the hydrolysis of AB and MeAB. Hence, this general method indicates that MeAB can be used as both a potential hydrogen storage material and an efficient reducing agent, and can be easily extended to facile preparation of other graphene supported multi-metal NPs.

Well-dispersed magnetically recyclable core–shell Ag@M (M = Co, Ni, Fe) nanoparticles (NPs) supported on graphene have been synthesized via a facile in situ one-step procedure, using methylamine borane (MeAB) as a reducing agent under ambient condition. Their catalytic activity toward hydrolysis of ammonia borane (AB) were studied. Although the Ag@Fe/graphene NPs are almost inactive, the as-prepared Ag@Co/graphene NPs are the most reactive catalysts, followed by Ag@Ni/graphene NPs. Compared with AB and NaBH4, the as-synthesized Ag@Co/graphene catalysts which reduced by MeAB exert the highest catalytic activity. Additionally, the Ag@Co NPs supported on graphene exhibit higher catalytic activity than the catalysts with other conventional supports, such as the SiO2, carbon black, and γ-Al2O3. The as-synthesized Ag@Co/graphene NPs exert satisfied catalytic activity, with the turnover frequency (TOF) value of 102.4 (mol H2 min–1 (mol Ag)−1), and the activation energy Ea value of 20.03 kJ/mol. Furthermore, the as-synthesized Ag@Co/graphene NPs show good recyclability and magnetically reusability for the hydrolytic dehydrogenation of AB and MeAB, which make the practical reusing application of the catalysts more convenient. Moreover, this simple synthetic method indicates that MeAB could be used as not only a potential hydrogen storage material but also an efficient reducing agent. It can be easily extended to facile preparation of other graphene supported metal NPs.Keywords: ammonia borane; core−shell NPs; graphene; hydrogen storage; methylamine borane;

•One-step synthesize Ru NPs supported on graphene.•Using methylamine borane as reducing agent get the best catalytic activity.•Lowest activation energy value ever reported for catalytic hydrolysis of AB.Ru nanoparticles supported on graphene have been synthesized via a one-step procedure using methylamine borane as reducing agent. Compared with NaBH4 and ammonia borane, the as-prepared Ru/graphene NPs reduced by methylamine borane exhibit superior catalytic activity towards the hydrolytic dehydrogenation of ammonia borane. Additionally, the Ru/graphene NPs exhibit higher catalytic activity than its graphene free counterparts, and retain 72% of their initial catalytic activity after 4 reaction cycles. A kinetic study shows that the catalytic hydrolysis of ammonia borane is first order with respect to Ru concentration, the turnover frequency is 100 mol H2 min−1 (mol Ru)−1. The activation energy for the hydrolysis of ammonia borane in the presence of Ru/graphene NPs has been measured to be 11.7 kJ/mol, which is the lowest value ever reported for the catalytic hydrolytic dehydrogenation of ammonia borane.

In this study, well dispersed Cu@Co core–shell nanoparticles (NPs) on rGO surfaces were successfully synthesized via a one-step in situ procedure using methylamine borane (MeAB) as reductant under ambient conditions. The Cu@Co/rGO NPs exhibit superior catalytic activity than their alloy (CuCo/rGO) and graphene-free (Cu@Co) counterparts toward the hydrolytic dehydrogenation of ammonia borane (AB). Additionally, compared with the NPs reduced by AB, the as-synthesized Cu@Co/rGO NPs generated by the weaker reducing agent MeAB exhibit higher catalytic activities. Furthermore, the as-synthesized NPs exerted satisfactory catalytic activities and recycle stabilities for the hydrolysis of MeAB. Moreover, this general method indicates that MeAB can be used as both a potential hydrogen storage material and an efficient reductant which can be easily extended to the facile preparation of other rGO-supported metal NPs.

Amorphous nickel catalysts derived from nickel halides (NiF2, NiCl2, NiBr2, NiI2) were in situ synthesized in an aqueous solution of NaBH4/NH3BH3. The halide anions have effects on the formation of Ni(0) catalysts, which can further affect the catalytic activities and activation energies of the catalysts for the hydrolysis of ammonia borane. The PVP stabilized catalysts have higher hydrogen evolution rates and durabilities than bare Ni catalysts for the hydrolysis of ammonia borane. The catalysts derived from NiBr2 stabilized by PVP present the highest catalytic activity and the lowest activation energy, which has been measured to be 25.58 kJ/mol. This value is lower than most of reported Ni-based catalysts and even noble-metal containing catalysts. The results of mercury poisoning experiment reveal that Ni(0) catalysts derived from NiBr2 are heterogeneous catalysts in the hydrolysis of ammonia borane.

It was considered that the dissolution of cellulose in alkali solutions is mainly due to the breakage of hydrogen bonds. As an alkali hydroxide, KOH can provide OH− just like LiOH and NaOH; but it is well known that LiOH and NaOH can dissolve cellulose, whereas KOH can only swell cellulose. The inability of KOH to dissolve cellulose was investigated and the mechanism of cellulose dissolving in alkali solutions was proposed. The dissolution behavior of cellulose and cellobiose in LiOH, NaOH and KOH were studied by means of 1H and 13C NMR as well as longitudinal relaxation times. The structure and properties of the three alkali solutions were compared. The results show that alkali share the same interaction mode with cellobiose and with the magnitude of LiOH > NaOH > KOH; the alkalis influence the structure of water also in the same order LiOH > NaOH > KOH. The different behavior of the three alkalis lies in the different structure of the cation hydration ions. Li+ and Na+ can form two hydration shells, while K+ can only form loose first hydration shell. The key to the alkali solution can or cannot dissolve cellulose is whether the cation hydration ions can form stable complex with cellulose or not. K+ cannot form stable complex with cellulose result in the KOH solution can only swell cellulose.

An asymmetrical bis-pyridine pendant-armed macrocyclic heterobinuclear complex, [ZnNiL](ClO4)2·CH3CN (H2L was derived from the condensation between 3,3′-((ethane-1,2-diylbis((pyridin-2-ylmethyl)azanediyl))bis(methylene))bis(2-hydroxy-5-methylbenzaldehyde) and 1.3-diaminopropane), has been synthesized and characterized by physico-chemical and spectroscopic methods. The asymmetric unit contains two complete macrocyclic complexes that are nevertheless quite similar to one another. The Zn–Ni separations, bridged by the two phenoxides, are 3.107 and 3.141 Ǻ, respectively. The phosphate hydrolysis catalyzed by the complex was investigated using bis(4-nitrophenyl)phosphate (BNPP) as the substrate. The catalytic rate constant (kcat) is 1.64 × 10−3 s−1 at pH 7.4 and 25 °C, which is 108-fold higher than that of the corresponding uncatalyzed reaction. The interaction between the complex and calf thymus (CT) DNA was investigated by UV–vis absorption, viscosity experiments, and cyclic voltammetry. The complex shows good binding propensity to calf thymus DNA via intercalation with a binding constant of 5 × 104 M−1. The agarose gel electrophoresis studies show that the complex has a concentration-dependent DNA cleavage activity.

The solution microstructure variations with concentration of propylene glycol (PG)–water mixture were investigated using NMR technique. PG has an apparent critical point at around χPG = 0.3, this biphasic behavior of alkyl protons in PG–water mixture is different from the monotonous increase or decrease of other alcohol-water mixtures. At water-rich region, water molecules are in the vicinity of PG, forming weak C–H⋯O H-bonds with PG alkyl protons and strong O–H⋯O H-bonds with PG hydroxyls. PG gradually aggregates in the order of CH3, CH and CH2 with PG concentration increasing. At PG-rich region, the solution forms regions enriched in either hydrocarbons or hydroxyl groups, which results in the formation of microheterogeneous solution, where water is expelled from alkyl tail and accumulated in the region of PG hydroxyls head. In addition, the T1 and NOE results of PG aqueous solutions also support the weak hydrogen bond and microheterogeneous structural variations with concentration at molecular level. These results offer not only new insights into the mechanism of the outstanding capability of PG as cryoprotectant, but also provide possible reason of the anomalous thermodynamic behavior in the PG–water mixture.

Two new trinuclear complexes, Cu3L2(py)2 (1) and Ni3L2(py)4 (2), have been synthesized and characterized, where L3− is N-2-methyl-acryloyl-salicylhydrazidate. Central metal ion and two terminal metal ions in the two complexes are combined by two bridging deprotonated L3− ligands, forming a bent trinuclear structure unit with an M–N–N–M–N–N–M core. The bent angles in complexes 1 and 2 are 167.6(1)° and 75.4(1)°, respectively. Three nickel ions in compound 2 exhibit alternating square-planar and octahedral geometries, while three copper ions in compound 1 follow square-planar mode. The studies in solution integrity and stability of compounds 1 and 2 show they are soluble and stable in DMF. UV–Vis titrations demonstrate compound 1 is stable in DMF even in the presence of excess metal ions. Antibacterial screening data indicate the two compounds all have stronger antimicrobial activities against the tested microorganisms than ligand. The trinuclear copper compound 1 is more active than monocopper compounds in the previous study, and the trinuclear nickel compound 2 is less active than tetranuclear nickel compound in the previous study.Two new trinuclear complexes, Cu3L2(py)2 (1) and Ni3L2(py)4 (2), have been synthesized and characterized, where L3− is N-2-methyl-acryloyl-salicylhydrazidate. Central metal ion and two terminal metal ions in the two complexes are combined by two bridging deprotonated L3− ligand, forming a bent trinuclear structure unit with a M–N–N–M–N–N–M core. The bent angles in complexes 1 and 2 are 167.6(1)° and 75.4(1)°, respectively. Three nickel ions in complex 2 exhibit alternating square-planar and octahedral geometries, while three copper ions in complex 1 follow square-planar mode.

Four novel trinuclear copper(II)/nickel(II) complexes with four trianionic pentadentate ligands, N-(3-t-butylbenzoyl)-5-nitrosalicylhydrazide (H33-t-bbznshz), N-(3,5-dimethylbenzoyl)salicylhydrazide (H33,5-dmbzshz), N-(phenylacetyl)-5-bromosalicylhydrazide (H3pabshz) and N-(3-t-butylbenzoyl)salicylhydrazide (H33-t-bbzshz) have been synthesized and characterized by X-ray crystallography. These trinuclear compounds all have an M–N–N–M–N–N–M core formed by three metal ions and two ligands. The geometries of three Cu(II) ions in compound Cu3(3-t-bbznshz)2(H2O)(DMF)(py)2 · DMF (1) alternate between distorted square pyramidal and square planar, while in compound Cu3(3,5-dmbzshz)2(py)2 (2), they are all square planar. Three Ni(II) ions in compound Ni3(pabshz)2(DMF)2(py)2 (3) and Ni3(3-t-bbzshz)2(py)4 · 2H2O (4) follow square-planar/octahedral/square-planar coordination geometry. Compounds 1, 2 and 4 are bent trinuclear, with the bend angles of 156.4°, 141.49° and 127.1°, respectively, while the three nickel ions in compound 3 are strictly linear, with an angle of 180°. Studies on the trinuclear Ni(II) complexes show that the β-branched N-acylsalicylhydrazide ligands with sterically flexible Cα methylene groups are easier to yield linear trinuclear Ni(II) complexes, while α-branched N-acylsalicylhydrazides ligands tend to form bent trinuclear Ni(II) complexes. Antibacterial screening data indicate that the trinuclear Cu(II) compound 2 is more active than 1 and mononuclear Cu(II) compound, bent trinuclear Ni(II) compound 4 is more active than linear compound 3 and less active than tetranuclear nickel compound in the previous study.Four novel trinuclear compounds Cu3(3-t-bbznshz)2(H2O)(DMF)(py)2 · DMF (1), Cu3(3,5-dmbzshz)2(py)2 (2), Ni3(pabshz)2(DMF)2(py)2 (3) and Ni3(3-t-bbzshz)2(py)4 · 2H2O (4) have been obtained by the reaction of metal salts with four novel trianionic pentadentate ligands, N-(3-t-butylbenzoyl)-5-nitrosalicylhydrazide, N-(3,5-dimethylbenzoyl)salicylhydrazide, N-(phenylacetyl)-5-bromosalicylhydrazide and N-(3-t-butylbenzoyl)salicylhydrazide. The coordination modes of the ligands are the same, but the metal ions show different coordination environments. Compounds 1, 2 and 4 are bent trinuclear, with the bent angles larger than 120°, while the three nickel ions in compound 3 are strictly linear, with an angle of 180°. They all get a M–N–N–M–N–N–M core formed by three metal ions and two ligands.

Well dispersed magnetically recyclable trimetallic core–shell Ag@CoNi nanoparticles (NPs) supported on graphene have been synthesized via a facile one-step in situ procedure using methylamine borane (MeAB) as the reducing agent. The as-synthesized NPs exhibit much higher catalytic activities for hydrolytic dehydrogenation of ammonia borane (AB) than the monometallic, bimetallic, trimetallic alloy (AgCoNi/graphene), and graphene free (Ag@CoNi) counterparts. Moreover, compared with NaBH4 and AB, the weaker reducing agent MeAB has much better control during the synthesis of the graphene supported Ag@CoNi NPs, which resulted in the highest catalytic activity. Kinetic studies indicate that the catalytic hydrolysis of AB by the Ag@CoNi/graphene NPs is first order, with the activation energy measured to be 36.15 kJ mol−1. Furthermore, the as-prepared NPs exert good catalytic activities and recycle stabilities towards the hydrolysis of AB and MeAB. Hence, this general method indicates that MeAB can be used as both a potential hydrogen storage material and an efficient reducing agent, and can be easily extended to facile preparation of other graphene supported multi-metal NPs.