Improved catalytic performance of metal oxide catalysts fabricated with electrospinning in ammonia borane methanolysis for hydrogen production

Electrospun Ni and Cu metal oxide catalysts are successfully synthesized through electrospinning and conventional sol-gel methods to show advantages of electrospinning on catalytic performance in ammonia borane (NH₃BH₃) methanolysis for hydrogen production. An experimental assessment is presented by the characterization of interior and exterior properties of all catalysts and their catalytic activity towards NH₃BH₃ methanolysis. The systematic studies are performed in order to figure out of kinetic interpretation. Catalytic NH₃BH₃ methanolysis reactions are carried out at different catalyst amounts (5–15 mg), initial NH₃BH₃ concentrations (0.36–6.0 M) and temperatures (20–50 °C). Thanks to the higher pore volume/S_BET ratio, fiber type nanostructured Cu oxide catalyst exhibits the highest catalytic activity compared with sol-gel prepared ones. The results of kinetic studies show that the fiber type Cu oxide catalyst catalyzed methanolysis of NH₃BH₃ and follows the first order reaction kinetic model with 35 kJ mol⁻¹ activation energy value.     

Ultrafine cobalt–molybdenum–boron nanocatalyst for enhanced hydrogen generation property from the hydrolysis of ammonia borane

The hydrolysis of ammonia borane (NH₃BH₃) is recognized as an efficient way of hydrogen generation if it can be effectively catalyzed. In this work, a series of cobalt–molybdenum–boron (Co–Mo–B) nanoparticles (NPs) on copper (Cu) foil are introduced as catalysts for NH₃BH₃ hydrolysis by electroless deposition method. The influence of the depositing pH value on the catalytic property is investigated by adjusting the pH value ranged from 10.5 to 12.0. By optimizing the value to 11, the ultrafine Co–Mo–B NPs with the grain size around 4.3 nm show the best catalytic property for NH₃BH₃ hydrolysis. The hydrogen generation rate reaches 5818.0 mL·min⁻¹·g⁻¹ when the hydrolysis temperature is 298 K. The thermodynamic tests show that the lower activation energy (E_a) is estimated to be 59.3 kJ·mol⁻¹. It can be found that the catalytic property in this work overtakes that of partial non-precious metal NPs, and is even better than some precious metal NPs previously reported. The hydrolysis reaction of NH₃BH₃ catalyzed by ultrafine Co–Mo–B NPs is a non-spontaneous process. In addition, the cycling ability of the ultrafine Co–Mo–B NPs is also studied and the results demonstrate that the catalyst is a recyclable one toward the hydrolysis of NH₃BH₃ under mild reaction conditions.     

Room temperature hydrogen generation from hydrolysis of ammonia–borane over an efficient NiAgPd/C catalyst

NiAgPd nanoparticles are successfully synthesized by in-situ reduction of Ni, Ag and Pd salts on the surface of carbon. Their catalytic activity was examined in ammonia borane (NH₃BH₃) hydrolysis to generate hydrogen gas. This nanomaterial exhibits a higher catalytic activity than those of monometallic and bimetallic counterparts and a stoichiometric amount of hydrogen was produced at a high generation rate. Hydrogen production rates were investigated in different concentrations of NH₃BH₃ solutions, including in the borates saturated solution, showing little influence of the concentrations on the reaction rates. The hydrogen production rate can reach 3.6–3.8 mol H₂ mol_cat⁻¹ min⁻¹ at room temperature (21 °C). The activation energy and TOF value are 38.36 kJ/mol and 93.8 mol H₂ mol_cat⁻¹ min⁻¹, respectively, comparable to those of Pt based catalysts. This nanomaterial catalyst also exhibits excellent chemical stability, and no significant morphology change was observed from TEM after the reaction. Using this catalyst for continuously hydrogen generation, the hydrogen production rate can be kept after generating 6.2 L hydrogen with over 10,000 turnovers and a TOF value of 90.3 mol H₂ mol_cat⁻¹ min⁻¹.     

Ammonia decomposition over SiO2-supported Ni–Co bimetallic catalyst for COx-free hydrogen generation

NH₃ decomposition over non-noble catalyst to generate CO_x-free H₂ has attracted great attention in recent years. In this work, fumed SiO₂-supported Ni, Co and Ni–Co bimetallic catalysts are synthesized by using a co-impregnation method and evaluated for NH₃ decomposition, which shows that the bimetallic catalysts exhibit better catalytic activity than the monometallic ones. This enhanced activity observed on bimetallic catalyst can be largely attributed to the more appropriate catalyst metal-N binding energy resulting from the synergistic effect between Ni and Co in the formed Ni–Co alloy. Among the synthesized catalysts, Ni₅Co₅/SiO₂ synthesized with the Ni/Co molar ratio of 5:5 achieves 76.8% NH₃ conversion under a GHSV of 30,000 mL h⁻¹ g⁻¹_cat at 550 °C and shows the best catalytic activity, which can be further improved by doping with K (78.1% NH₃ conversion at 30,000 mL h⁻¹ g⁻¹_cat), and the obtained Ni₅Co₅/SiO₂–K also shows excellent catalytic stability.     

Bimetallic RuCo and RuCu catalysts supported on γ-Al2O3. A comparative study of their activity in hydrolysis of ammonia-borane

Bimetallic-based RuCo and RuCu catalysts, supported on γ-Al₂O₃ (1.5 wt% Ru as theoretical value), were synthesized by polyol method. Ru, Co, and Cu acetylacetonates were used as precursors and ethylene glycol as reducing agent. The as-synthesized catalysts were characterized by SEM, TEM, XRD and XPS, and tested in ammonia-borane (NH₃BH₃) hydrolytic dehydrogenation at variable amount of catalyst (10-30 wt%), concentration of NH₃BH₃ (1.0-0.65 M), and temperatures (50-65 °C). The reactions were monitored by volumetric (inverted burette) and spectroscopic methods (¹¹B and ¹¹B{¹H} NMR). It was found that the best bimetallic catalysts are those having a molar ratio Ru:Co and Ru:Cu of 1:1 such as RuCo > RuCu ∼ Ru. They, i.e. RuCo and RuCu, consist of nanosized spherical particles of Ru⁰Co(OH)₂ and Ru⁰Cu⁰, respectively. Kinetic investigation highlights similar rate laws with activation energies of 47 kJ mol⁻¹ and 52 kJ mol⁻¹, respectively, and, for both, reaction orders of 1 versus both the NH₃BH₃ and the catalytic free sites concentrations. ¹¹B and ¹¹B{¹H} NMR investigation confirmed (i) a more effective NH₃BH₃ hydrolytic dehydrogenation in the presence of RuCo catalyst even though a loss of activity after the first run was observed for both catalysts, and (ii) a rapid NH₃BH₃ hydrolysis with initial formation of B(OH)₄⁻, which besides favors equilibriums of formation of polyborates. These results are reported and the reaction mechanism discussed herein.     

Carbon supported bimetallic Ru‐Co catalysts for H2 production through NaBH4 and NH3BH3 hydrolysis

This work investigates the effect of the addition of small amounts of Ru (0.5‐1 wt%) to carbon supported Co (10 wt%) catalysts towards both NaBH₄ and NH₃BH₃ hydrolysis for H₂ production. In the sodium borohydride hydrolysis, the activity of Ru‐Co/carbon catalysts was sensibly higher than the sum of the activities of corresponding monometallic samples, whereas for the ammonia borane hydrolysis, the positive effect of Ru‐Co systems with regard to catalytic activity was less evident. The performances of Ru‐Co bimetallic catalysts correlated with the occurrence of an interaction between Ru and Co species resulting in the formation of smaller ruthenium and cobalt oxide particles with a more homogeneous dispersion on the carbon support. It was proposed that Ru^°, formed during the reduction step of the Ru‐Co catalysts, favors the H₂ activation, thus enhancing the reduction degree of the cobalt precursor and the number of Co nucleation centers. A subsequent reduction of cobalt and ruthenium species also occurs in the hydride reaction medium, and therefore the state of the catalyst before the catalytic experiment determines the state of the active phase formed in situ. The different relative reactivity of the Ru and Co active species towards the two investigated reactions accounted for the different behavior towards NaBH₄ and NH₃BH₃ hydrolysis.     

CoMoB nanoparticles supported on foam Ni as efficient catalysts for hydrogen generation from hydrolysis of ammonia borane solution

We report on CoMoB nanoparticles supported on foam Ni as catalysts for hydrogen generation from hydrolysis of ammonia borane (NH₃BH₃) solution. The CoMoB/foam Ni catalysts with different molar ratios of Co²⁺and MoO₄²⁻ were synthesized via the electroless-deposition technique at ambient temperature. In order to analyze the phase composition, chemical composition, microstructure, and electron bonding structure of the as-prepared samples, powder X–ray diffraction (XRD), inductively coupled plasma-mass spectroscopy (ICP-MS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used. The results showed that CoMoB nanoparticles were variously dispersed on the surface of the foam Ni and the catalytic activity correlated with the molar ratio of Co²⁺ and MoO₄²⁻. The highest hydrogen generation rate was 5331.0 mL min⁻¹ g_cat⁻¹ at 298 K, and the activation energy was calculated to be 45.5 kJ mol⁻¹ toward the hydrolysis of NH₃BH₃ solution. The better catalytic activity was largely attributed to the smaller particle size, higher surface roughness and the novel three-dimensional cone-like architectures of the obtained samples. The kinetic results show that the hydrolysis of NH₃BH₃ is a first-order reaction in catalyst concentration. In addition, the reusability experiment exhibited that the catalytic activity was reduced after 5 cycles and the reason of the decay was also investigated.     

Preparation and catalytic activity of thin-film cobalt–tungsten–boron for the hydrolysis of ammonia borane

In this work, cobalt–tungsten–boron nanoparticles (Co–W–B) have been successfully deposited on foam Ni to manufacture thin-film catalysts by electroless plating technique and applied in hydrogen generation from ammonia borane (NH₃BH₃) hydrolysis. Physicochemical properties of Co–W–B nanoparticles are characterized by XRD (Powder X–ray diffraction), SEM (Scanning electron microscopy), and EDS (Energy dispersive X–ray spectroscopy). It is observed that Co–W–B showed irregular spherical structure on the surface of foam Ni substrate. An increase of depositional pH value in the preparation process leads to the change of particle size. When the pH value is equal to 11.5, as-synthesized Co–W–B exhibits the smaller particle size, which suggests that depositional pH value has directly impacted the nucleation and growth of catalysis particles. The optimized Co–W–B catalyst displays higher catalytic activity toward NH₃BH₃ hydrolysis with a specific rate of hydrogen generation of 12933.3 mL min^?1·g^?1 at room temperature. Moreover, the lower apparent activation energy of 47.3 kJ mol^?1 is achieved. Compared with previously reported catalysts, the as-obtained catalytic performance is situated at the better rank. Moreover, the reusability has been investigated under the mild NH₃BH₃ hydrolysis conditions. It reveals that as-fabricated thin-film Co–W–B maintains excellent durability after five cycles. A possible mechanism for the released hydrogen from NH₃BH₃ hydrolysis using Co–W–B catalyst has been proposed.     

Hydrogen release mechanism and performance of ammonia borane catalyzed by transition metal catalysts Cu‐Co/MgO(100)

The catalytic dehydrogenation of ammonia borane (NH₃BH₃, AB) molecule is most frequently employed by metal catalysts, but a reliable dehydrogenation mechanism in molecular level has yet to be fully illuminated. Herein, adopting the density functional theory (DFT) method, the dehydrogenation mechanism and performance of NH₃BH₃ under the transition metal catalysts (Cu/MgO, Co/MgO, CuCo/MgO) were studied. The calculated results show that the dehydrogenation mechanism of AB refers to stepwise dehydrogenation mechanism: AB is adsorbed in the transition metal catalysts firstly, then one H(N) atom transferred to H(B) of ―BH₃ and to form H₂ molecule via the broken of B―H and N―H bond, finally, H₂ molecule desorption from the catalyst complexes. Among the transition metal catalysts, CuCo/MgO have the perfect catalytic activity in dehydrogenation reaction of NH₃BH₃, its barrier energy of the feasible pathway (path A) is 22.26 kcal/mol, which is lower than the barrier energy of AB‐Cu/MgO(28.13 kcal/mol), AB‐Co/MgO(27.46 kcal/mol), and the results of thermogravimetric analysis further verified the reasonability of DFT calculational results. Besides, partial density of states calculational results show the electron orbital hybridization of Cu, Co atom may account for the excellent catalytic performance of CuCo/MgO(100) compared with the Cu/MgO(100) and Co/MgO(100) in dehydrogenation process of AB.     

FeCo alloys in-situ formed in Co/Co2P/N-doped carbon as a durable catalyst for boosting bio-electrons-driven oxygen reduction in microbial fuel cells

Non-noble metal catalyst with high catalytic activity and stability towards oxygen reduction reaction (ORR) is critical for durable bioelectricity generation in air-cathode microbial fuel cells (MFCs). Herein, nitrogen-doped (iron-cobalt alloy)/cobalt/cobalt phosphide/partly-graphitized carbon ((FeCo)/Co/Co₂P/NPGC) catalysts are prepared by using cornstalks via a facile method. Carbonization temperature exerts a great effect on catalyst structure and ORR activity. FeCo alloys are in-situ formed in the catalysts above 900 °C, which are considered as the highly-active component in catalyzing ORR. AC-MFC with FeCo/Co/Co₂P/NPGC (950 °C) cathode shows the highest power density of 997.74 ± 5 mW m^?2, which only declines 8.65% after 90 d operation. The highest Coulombic efficiency (23.3%) and the lowest charge transfer resistance (22.89 Ω) are obtained by FeCo/Co/Co₂P/NPGC (950 °C) cathode, indicating that it has a high bio-electrons recycling rate. Highly porous structure (539.50 m² g^?1) can provide the interconnected channels to facilitate the transport of O₂. FeCo alloys promote charge transfer and catalytic decomposition of H₂O₂ to ?OH and ?O₂^?, which inhibits cathodic biofilm growth to improve ORR durability. Synergies between metallic components (FeCo/Co/Co₂P) and N-doped carbon energetically improve the ORR catalytic activity of (FeCo)/Co/Co₂P/NPGC catalysts, which have the potential to be widely used as catalysts in MFCs.     

Hydrolytic dehydrogenation of ammonia borane catalyzed by carbon supported Co core-Pt shell nanoparticles

Co core-Pt shell nanoparticles (denoted as Co_1−x@Pt_x where x = 0.33, 0.43, 0.60, 0.68, 0.82) and carbon supported Co core-Pt shell nanoparticles (denoted as Co_1−x@Pt_x/C where x = 0.60, 0.68, 0.82) (Co_1−x@Pt_x/C = 43%), which are synthesized through a polyol reduction process with oleic acid as a surfactant, have been investigated as catalysts for hydrogen generation from hydrolysis of ammonia borane (NH₃BH₃) at 25 ± 0.5 °C. The as-prepared Co core-Pt shell nanoparticles are uniformly dispersed on carbon surface with diameters of about 3 nm. It is found that the catalysts show favorable performance toward the hydrolysis of NH₃BH₃ and the catalytic activity is associated with the ratio of Pt to Co. Among the catalysts studied, Co_0.32@Pt_0.68/C (Co_0.32@Pt_0.68/C = 43%) displays the highest catalytic performance, delivering a high hydrogen-release rate of 4874 mL min⁻¹ g⁻¹ (per catalyst).     

Catalytic activities of non-noble metals for hydrogen generation from aqueous ammonia–borane at room temperature

We have studied catalytic performance of supported non-noble metals for hydrogen generation from aqueous NH₃BH₃ at room temperature. Among the tested non-noble metals, supported Co, Ni and Cu are the most catalytically active, with which hydrogen is released with an almost stoichiometric amount from aqueous NH₃BH₃, whereas supported Fe is catalytically inactive for this reaction. Support effects on the catalytic activity have been investigated by testing the hydrogen generation reaction in the presence of Co supported on γ-Al₂O₃, SiO₂ and C and it is found that the Co/C catalyst has higher activity. Activation energy for hydrogen generation from aqueous NH₃BH₃ in the presence of Co/γ-Al₂O₃ was measured to be 62 kJ mol⁻¹; this may correspond to the step of BN bond breaking. Particle size, surface morphology and surface area of the supported metal catalysts were examined by X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive X-ray (EDX) and BET experiments. It is found that with decreasing the particle size the activity of the supported catalyst is increased. The low-cost and high-performance supported non-noble metal catalysts may have high potential to find its application to the hydrogen generation for portable fuel cells.     

Dehydrogenation characteristics of ammonia borane via boron-based catalysts (Co–B,Ni–B,Cu–B) under different hydrolysis conditions

In the present study, dehydrogenation characteristics of ammonia borane (NH₃BH₃) catalyzed via boron-based catalysts under different hydrolysis conditions were investigated. A series of boron-based catalysts (Co_1−x–B_x, Ni_1−x–B_x, and Cu_1−x–B_x, x: 0.25, 0.50, 0.75) were prepared by sol–gel method. Gels were calcinated at different temperatures (250 °C, 350 °C, and 450 °C) in order to obtain the boron-based catalysts. XRD characterizations revealed that Co–B, Ni–B, and Cu–B crystalline structures were formed during calcination at 450 °C. Hydrogen generation measurements were performed in order to determine the optimum composition of the boron-based catalyst. The maximum hydrogen generation rates were 7607 ml min⁻¹ gcat⁻¹, 3869 ml min⁻¹ gcat⁻¹ and 1178 ml min⁻¹ gcat⁻¹ for Co_0.75B_0.25, Ni_0.75B_0.25 and Cu_0.75B_0.25, respectively. Furthermore, the hydrolysis of NH₃BH₃ was performed at 20 °C, 40 °C, 60 °C and 80 °C under magnetic stirring (750 rpm), ultrasonic irradiation and non-stirring in order to determine how these parameters effect hydrolysis. Activation energies (E_a) were calculated by evaluation of the kinetic data. Under ultrasonic irradiation, the E_a in the presence of Co_0.75B_0.25, Ni_0.75B_0.25 and Cu_0.75B_0.25 were 40.85 kJ mol⁻¹, 43.19 kJ mol⁻¹ and 48.74 kJ mol⁻¹, respectively, which compares favorably with results reported in the literature. Thus, the catalytic activities of the boron-based catalysts were found to be Cu < Ni < Co and the best reaction condition for the catalytic hydrolysis of NH₃BH₃ was determined to be non-stirring < magnetic stirring < ultrasonic irradiation.     

Synthesis of Cu@FeCo core–shell nanoparticles for the catalytic hydrolysis of ammonia borane

Non-noble Cu@FeCo core–shell nanoparticles (NPs) containing Cu cores and FeCo shells have been successfully in situ synthesized via a facile chemical reduction method. The NPs exerted composition-dependent activities towards the catalytic hydrolysis of ammonia borane (NH₃BH₃, AB). Among them, the Cu_0.3@Fe_0.1Co_0.6 NPs showed the best catalytic activity, with which the max hydrogen generation rate of AB can reach to 6674.2 mL min⁻¹ g⁻¹ at 298 K. Kinetic studies demonstrated that the hydrolysis of AB catalysed by Cu_0.3@Fe_0.1Co_0.6 NPs was the first order with respect to the catalyst concentration. The activation energy (Ea) was calculated to be 38.75 kJ mol⁻¹. Furthermore, the TOF value (mol of H₂. (mol of catalyst. min)⁻¹) of Cu_0.3@Fe_0.1Co_0.6 NPs was 10.5, which was one of the best catalysts in the previous reports. The enhanced catalytic activity was largely attributed to the preferable synergistic effect of Cu, Fe and Co in the special core–shell structured NPs.     

MgFe and Mg–Co–Fe mixed oxides derived from hydrotalcites: Highly efficient catalysts for COx free hydrogen production from NH3

Mg–Fe Layered Double Hydroxide (LDH) with M²⁺: M³⁺ 3:1 stoichiometric ratio was synthesized and employed as catalyst precursor for CO_x-free hydrogen production from ammonia. The resulting catalyst showed good catalytic activity. A series of Mg/Co–Fe layered double hydroxides were synthesized by replacing Mg²⁺ with Co²⁺ without disturbing M²⁺:M³⁺ ratio. The influence of nature and extent of Co(II) substitution on structure, morphology and surface properties were studied. A systematic study was carried out using these materials as catalyst precursors for ammonia decomposition. BET, XRD, TPR, XPS, CO₂-TPD and TEM techniques were used to characterize the synthesized catalysts. These Fe-based catalysts are highly active, highly stable and not promoting any stable surface nitridation during the ammonia decomposition reaction. Among all catalysts, the Mg₃Co₃Fe₂ catalyst showed the highest activity i.e. 100% conversion at 6,000 h⁻¹ and 60% at 50,000 h⁻¹ space velocities at 550 °C. The registered superior catalytic activity was result of the formed specific catalyst's properties like high surface area, high surface Co and Fe atomic concentration and suitable basicity. These Fe-based materials are, cost-effective, easily synthesize and highly stable, thus attractive for large-scale operation.     

Epoxy-activated acrylic particulate polymer-supported Co–Fe–Ru–B catalyst to produce H2 from hydrolysis of NH3BH3

Epoxy-activated acrylic particulate polymer, namely Eupergit CM, supported Co–Fe–Ru–B catalyst (EP/Co–Fe–Ru–B) for the first time was used to produce H₂ from hydrolysis of NH₃BH₃. The EP/Co–Fe–Ru–B showed very effective performance in the production of H₂ from the hydrolysis of NH₃BH₃. Various techniques such as XRD, SEM-EDS, ICP-OES, and TEM have been used to characterize these catalysts. The parameters on the hydrolysis reaction of NH₃BH₃ such as the effect of metal amount, the effect of Ru percentage, the effect of NH₃BH₃ concentration, the effect of NaOH concentration, the amount of catalyst, temperature, and catalyst durability were investigated in detail. Eupergit CM based polymer support and Ru particles have been found to be highly effective in H₂ production reactions. The hydrogen production rate (HGR) of the EP/Co–Fe–Ru–B catalyst was found to be 36,978 mL/min/g_cat, which was quite good compared to the values reported in the literature. In addition, the activation energy (Ea) of the polymer-supported Co–Fe–Ru–B catalyst was determined as 24.91 kJ/mol.     

Synthetic fuels from 3-φ Fischer-Tropsch synthesis using syngas feed and novel nanometric catalysts synthesised by plasma

Nanometric carbon-supported catalysts based on cobalt and iron (Co/C, Fe/C and CoFe/C) were synthesised by plasma method for application in Fischer-Tropsch synthesis (FTS). FTS tests were conducted at reaction conditions (ca 533 K, 2 MPa) over the catalyst, in a feed stream of 60% mol fraction H₂ and 30% mol fraction CO at 1.0 cm³s⁻¹g⁻¹ of catalyst for 24 h. Prior to this, the catalysts were pre-treated at 673 K either in pure H₂ or CO flowing at 250 cm³ min⁻¹ for 24 h. Results showed that higher temperature promoted better CO conversion; up to 100% for the Co/C catalyst at 533 K. However, lower temperatures were more conducive for the selectivity of Co/C catalyst towards gasoline (C₄C₁₂) and diesel (C₁₃C₂₀) fractions, since production of undesired products such as CO₂ and CH₄ was prevalent at higher temperatures. At 493 K, the CoFe/C bimetallics were almost inert, but at 533 K, they showed improved CO conversion. When compared to the Co/C catalyst, Fe-containing catalysts suppressed both CO₂ and CH₄ production. Moderated H₂O production was witnessed in the CO-reduced catalysts, contrasting with catalysts pre-treated in H₂ gas. Catalyst characterisation by BET surface area, XRD analysis and microscopy (SEM & TEM) showed that plasma synthesis produces catalysts with consistency, having highly dispersed nanoparticle metal moieties, interspersed with various forms of metallic, carbidic and intermetallic CoFe species in the carbon matrix support.     

In situ synthesized Fe–Co/C nano-alloys as catalysts for the hydrolysis of ammonia borane

Composite catalysts Fe_0.3Co_0.7-doped carbon aerogel have been in situ synthesized by chemical reduction method and successfully employed in the hydrolysis of NH₃BH₃ (AB) at room temperature. The mass percent of the doped Fe_0.3Co_0.7 alloys can reach to the maximum value of 40 wt%. The prepared catalysts exhibit excellent catalytic activity, especially for the specimen of 40 wt% Fe_0.3Co_0.7/C, which shows high catalytic activity and long durability. Its maximum hydrogen generation rate is as high as 13,695.6 ml min⁻¹ g⁻¹ at 298 K and the activation energy is only 20.83 kJ mol⁻¹. Besides, this catalyst possesses preferable cycling stability at room temperature. The low cost, high catalytic activity and enhanced cycling stability can make it have a bright future in the application field of fuel chemistry.     

The doped Co on Rh/Ni@Ni–N–C that weakened the catalytic performance for ammonia borane hydrolysis

Alloy catalyst has been widely studied and used for hydrolytic dehydrogenation of ammonia borane (NH₃BH₃, AB) with excellent catalytic performance due to the synergistic effect of bimetal. Herein, a series of Rh_1-xCo_x/Ni@Ni–N–C catalysts were prepared by an impregnation reduction method. The optimized Rh_0.75Co_0.25/Ni@Ni–N–C catalyst exhibited good catalytic performance with turnover frequency of 223.08 mol_H2 mol_cat^?1 min^?1 at 303 K, but decreased the catalytic performance compared with Rh/Ni@Ni–N–C. According to the XPS and Raman analysis, the RhCo alloy nanoparticles could be loaded at the defect position of Ni@Ni–N–C, and the Co nanoparticles occupied the intercalation between Rh and the defective site of the carrier, which could weaken the catalytic activity of AB hydrolysis. Based on the above research, we proposed the catalytic mechanism of the activation of the RhCo–H species. This work provides a new strategy for designing alloy-supported nano-catalysts.     

Hydrogen generation from hydrolysis of NH3BH3 by an electroplated Co–P catalyst

This paper investigates the effect of an electroplated Co–P catalyst on hydrogen generation kinetics from hydrolysis of NH₃BH₃. The Co–P catalyst is composed of an amorphous Co–P phase and Co nanoparticles. An increase in NH₃BH₃ concentration caused the hydrogen generation rate to increase dramatically. The Co–P catalyst shows a large hydrogen generation rate for 2 wt% NH₃BH₃ solution at 30 °C. This is 1.8 times higher than that of the Pt/C catalysts and 6 times higher than that of Ru catalysts. The activation energy for hydrolysis of NH₃BH₃ by the Co–P catalyst is calculated to be 22 kJ/mol, which is close to that of noble metal-based catalysts.