Solution combustion synthesized cobalt oxide catalyst precursor for NaBH4 hydrolysis

In this paper we report the solution combustion synthesis of cobalt oxide nanofoam from solutions of cobalt nitrate and glycine and subsequent use as an effective catalyst precursor for NaBH₄ hydrolysis. The catalytic activity results show that the hydrogen generation rate (HGR) at room temperature was much higher for the solution combustion synthesized material than for commercial Co₃O₄ nanopowder, though their specific surface areas were comparable (∼26–32 m²/g). Using a 0.6 wt.% aqueous solution of NaBH₄ at 20 °C and a 5 wt.% catalyst precursor loading, a HGR of 1.93 L min⁻¹ g_cat⁻¹ was achieved for solution combustion synthesized Co₃O₄. In contrast, at the same conditions, for commercial Co₃O₄ and elemental Co powders HGRs of 0.98 and 0.49 L min⁻¹ g_cat⁻¹ were achieved respectively. This type of synthesis is amenable to many complex metal oxide catalysts as well, such as LiCoO₂, which have also been shown to be good catalyst precursors for hydrolysis of NaBH₄.     

Effects of crystallinity and morphology of solution combustion synthesized Co3O4 as a catalyst precursor in hydrolysis of sodium borohydride

Solution combustion synthesized (SCS) cobalt oxide (Co₃O₄) powder has been studied as a catalyst precursor for the hydrolysis of sodium borohydride (NaBH₄). Synthesis is completed in less than two minutes and results indicate SCS is capable of reproducibly synthesizing 98.5–99.5% pure Co₃O₄ nano-foam materials. SCS materials demonstrate an as-synthesized specific surface area of 24 m² g⁻¹, a crystallite size of 15.5 nm, and fine surface structures on the order of 4 nm. Despite having similar initial surface areas and sample purities, SCS-Co₃O₄ outperforms commercially available Co₃O₄ and elemental cobalt (Co) nano powders when used as a catalyst precursor for NaBH₄ hydrolysis. Hydrogen generation rates (HGR) using 0.6 wt% NaBH₄ in aqueous solution at 20 °C were observed to be 1.24 ± 0.2 L min⁻¹ g_cat⁻¹ for SCS nano-foam Co₃O₄ compared to 0.90 ± 0.09 and 0.43 ± 0.04 L min⁻¹ g_cat⁻¹ for commercially available Co₃O₄ and Co, respectively. The high catalytic activity of SCS-Co₃O₄ is attributed to its nano-foam morphology and crystallinity. During the hydrolysis of NaBH₄, the SCS-Co₃O₄ converts in-situ to an amorphous active catalyst with a specific surface area of 92 m² g⁻¹ and exhibits a honeycomb type morphology.     

Catalytic hydrolysis of NaBH4 over titanate nanotube supported Co for hydrogen production

A Co/HTNT catalyst is developed by immobilizing Co on the surface of titanate nanotubes. The microstructure and composition of the catalyst are investigated with atomic absorption spectroscopy (AAS), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS). The developed Co/HTNT catalyst shows great performance in catalyzing NaBH₄ hydrolysis. The hydrolysis of 25 mg NaBH₄ catalyzed by 50 mg Co/HTNT in 10 g NaOH solution (12.5 wt%) provides a hydrogen production rate of 1.04 L min^?1 g_Co^?1 at 30 °C, and the activation energy of the reaction is 29.68 kJ mol^?1. The high catalytic activity and economical property make this catalyst a promising choice for on-site hydrogen production from NaBH₄ hydrolysis.     

Cobalt doped TiO2: A stable and efficient photocatalyst for continuous hydrogen production from glycerol: Water mixtures under solar light irradiation

Glycerol is the main by-product during the trans-esterification of vegetable oils to biodiesel. In this study, we investigate the process of photocatalytic hydrogen production from glycerol aqueous solution, with the use of cobalt doped TiO₂ photocatalyst under solar light irradiation. Cobalt doped TiO₂ photocatalysts are prepared by impregnation method and these catalysts are characterized by XRD, EDAX, DRS, TEM, EPR and XPS techniques. DRS studies clearly show the expanded photo response of TiO₂ into visible region on impregnation of Co²⁺ ions on surface of TiO₂. XPS studies also show change in the binding energy values of O1s, Ti 2p and Co 2p, indicating that Co²⁺ ions are in interaction with TiO₂. Maximum hydrogen production of 220 μ mol h⁻¹ g⁻¹ is observed on 2 wt% cobalt doped TiO₂ catalysts in pure water under solar irradiation. A significant improvement in hydrogen production is observed in glycerol: water mixtures; and maximum hydrogen production of 11,021 μ mol h⁻¹ g⁻¹ is obtained over 1 wt% cobalt doped TiO₂ in 5% glycerol aqueous solutions. Furthermore, to evaluate some reaction parameters such as cobalt wt% on TiO₂, glycerol concentration, substrate effect (alcohols) and pH of the solution on the hydrogen production activity are systematically investigated. When the catalysts are examined under UV irradiation, a 3–4 fold increase in activity is observed where this activity seems to decrease with time; however, a continuous activity is observed under solar irradiation on these catalysts. The decreased activity could be ascribed the loss of cobalt ions under UV irradiation, as evidenced by EDAX and TEM analysis. A possible explanation for the stable and continuous activity of cobalt doped TiO₂ photocatalysts under solar irradiation is proposed.     

Water soluble nickel(0) and cobalt(0) nanoclusters stabilized by poly(4-styrenesulfonic acid-co-maleic acid): Highly active, durable and cost effective catalysts in hydrogen generation from the hydrolysis of ammonia borane

This paper reports the in-situ generation and catalytic activity of nickel(0) and cobalt(0) nanoclusters stabilized by poly(4-styrene sulfonic acid-co-maleic acid), PSSA-co-MA, in the hydrolysis of ammonia borane (AB). PSSA-co-MA stabilized nickel(0) (PSMA-Ni) and cobalt(0) nanoclusters (PSMA-Co) having average particle size of 2.1 ± 0.6 and 5.3 ± 1.6 nm, respectively, were generated by in-situ reduction of nickel(II) chloride or cobalt(II) chloride in an aquoues solution of NaBH₄/H₃NBH₃ in the presence of PSSA-co-MA. The in-situ generated nanoclusters were isolated from the reaction solution and characterized by UV-Vis, TEM, XRD and FT-IR techniques. Compared with the previous catalyst systems, PSMA-Ni and PSMA-Co are found to be highly active catalysts for hydrogen generation from the hydrolysis of AB with the turnover frequency values of 10.1 min⁻¹ for Ni and 25.7 min⁻¹ for Co. They are also very stable during the hydrolysis of AB providing 22450 and 17650 turnovers, respectively. The results of mercury poisoning experiments reveal that PSMA-Ni and PSMA-Co are heterogeneous catalysts in the hydrolysis of AB. Herein, we also report the results of a detailed kinetic study on the hydrogen generation from the hydrolysis of AB catalyzed by PSMA-Ni and PSMA-Co depending on catalyst concentration, substrate concentration, and temperature along with the activation parameters of catalytic hydrolysis of AB calculated from the kinetic data.     

Hydrogen generation by hydrolysis of sodium borohydride on CoB/SiO2 catalyst

Generation of hydrogen by hydrolysis of alkali metal hydrides has attracted attention. Unsupported CoB catalyst demonstrated high activity for the catalytic hydrolysis of NaBH₄ solution. However, unsupported CoB nanoparticles were easy to aggregate and difficult to reuse. To overcome these drawbacks, CoB/SiO₂ was prepared and tested for this reaction. Cobalt (II) acetate precursor was loaded onto the SiO₂ support by incipient-wetness impregnation method. After drying at 100 °C, Co cations were deposited on the support. The dried sample was then dispersed in methanol/water solution and then fully reduced by NaBH₄ at room temperature. The catalyst was characterized by N₂ sorption, XRD and XPS. The results indicated that the CoB on SiO₂ possessed amorphous structure. B and Co existed both in elemental and oxidized states. SiO₂ not only affected the surface compositions of CoB, but also affected the electronic states of Co and B. B⁰ could donate partial electron to Co⁰. The structure effect caused by the SiO₂ support helped to prevent CoB nanocluster from aggregation and therefore the activity increased significantly on hydrolysis of alkaline NaBH₄ solution. The CoB/SiO₂ catalyst showed much higher activity than the unsupported CoB catalyst. At 298 K, the hydrogen generation rate on CoB/SiO₂ catalyst was 4 times more than that on the unsupported CoB catalyst. The hydrogen generation rate was as high as 10,586 mL min⁻¹ g⁻¹ catalyst at 298 K. CoB/SiO₂ is a very promising catalyst for this reaction.     

Accurately measuring the hydrogen generation rate for hydrolysis of sodium borohydride on multiwalled carbon nanotubes/Co–B catalysts

Multiwalled carbon nanotubes supported cobalt–boron catalysts (Co–B/MWCNT) were developed via the chemical reduction of aqueous sodium borohydride with cobalt chloride for catalytic hydrolysis of alkaline NaBH₄ solution. The hydrogen generation (HG) rates were measured on an improved high-accuracy, low-cost and automatic HG rate measurement system based on the use of an electronic balance with high accuracy. The HG of Co–B/MWCNT catalyst was investigated as a function of heat treatment, solution temperature, Co–B loading and supporting materials. The catalyst was mesoporous structured and showed lower activation energy of 40.40 kJ mol⁻¹ for the hydrolysis of NaBH₄. The Co–B/MWCNT catalyst was not only highly active to achieve the average HG rate of 5.1 l min⁻¹ g⁻¹ compared to 3.1 l min⁻¹ g⁻¹ on Co–B/C catalyst under the same conditions but also reasonably stable for the continuous hydrolysis of NaBH₄ solution.     

Hydrogen generation from catalytic hydrolysis of sodium borohydride solution using Cobalt–Copper–Boride (Co–Cu–B) catalysts

Co–Cu–B, as a catalyst toward hydrolysis of sodium borohydride solution, has been prepared through chemical reduction of metal salts, CoCl₂·6H₂O and CuCl₂, by an alkaline solution composed of 7.5wt% NaBH₄ and 7.5wt% NaOH. The effects of Co/Cu molar ratio, calcination temperature, NaOH and NaBH₄ concentration and reaction temperature on catalytic activity of Co–Cu–B for hydrogen generation from alkaline NaBH₄ solution have been studied. X-ray diffraction (XRD), scanning electron microscope (SEM) and Nitrogen adsorption–desorption isotherm have been employed to understand the results. The Co–Cu–B catalyst with a Co/Cu molar ratio of 3:1 and calcinated at 400 °C showed the best catalytic activity at ambient temperature. The activation energy of this catalytic reaction is calculated to be 49.6 kJ mol⁻¹.     

Multifunctional Co–B–O@CoxB catalysts for efficient hydrogen generation

The development of efficient and non-noble catalyst is of great significance to hydrogen generation techniques. Three surface-oxidized cobalt borides of Co–B–O@Co_xB (x = 0.5, 1 and 2) have been synthesized that can functionalize as active catalysts in both alkaline water electrolysis and the hydrolysis of sodium borohydride (NaBH₄) solution. It is discovered that oxidation layer and low boron content favor the oxygen evolution reaction (OER) activity of Co–B–O@Co_xB in alkaline water electrolysis. And surface-oxidized cobalt boride with low boron content is more active toward hydrolysis of NaBH₄ solution. An alkaline electrolyzer fabricated using the optimized electrodes of Co–B–O@CoB₂/Ni as cathode and Co–B–O@Co₂B/Ni as anode can deliver current density of 10 mA cm⁻² at 1.54 V for overall water splitting with satisfactory stability. Meanwhile, Co–B–O@Co₂B affords the highest hydrogen generation rate of 3.85 L min⁻¹ g⁻¹ for hydrolysis of NaBH₄ at 25 °C.     

Carbon-supported Ni3B nanoparticles as catalysts for hydrogen generation from hydrolysis of ammonia borane

We report the preparation of Ni₃B and carbon-supported Ni₃B (denoted as Ni₃B/C) nanoparticles, and their catalytic performance for hydrogen generation from hydrolytic dehydrogenation of ammonia borane (NH₃BH₃, AB). Ni₃B and Ni₃B/C were prepared via a chemical reduction and crystallization in tetraethylene glycol solution. The obtained Ni₃B catalysts are in well-defined crystalline state and Ni₃B/C catalysts have a high dispersion in the carbon. The hydrogen generation measurement shows that the carbon-supported Ni₃B presents enhanced catalyst activity during hydrolytic dehydrogenation of AB. Among the as-prepared Ni₃B/C catalysts, Ni₃B/C with 34.25 wt% Ni₃B loading displays the best catalytic activity, delivering a high hydrogen release rate of 1168 mL min⁻¹ g⁻¹ and the lower activation energy of 46.27 kJ mol⁻¹. The kinetic results show that the hydrolysis is a first-order reaction in catalyst concentration, while it is a zero-order in AB concentration. Furthermore, the Ni₃B/C is a recyclable catalyst under mild reaction conditions, indicating that the carbon-supported Ni₃B is a promising catalyst for AB hydrolytic dehydrogenation.     

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.     

Hydrolysis of AlLi/NaBH4 system promoted by Co powder with different particle size and amount as synergistic hydrogen generation for portable fuel cell

Hydrogen generation from the hydrolysis of aluminum lithium/sodium borohydride (referred to as AlLi/NaBH₄) system activated by Co powder with different particle size and amount was evaluated in this paper. The designed aluminum–lithium–cobalt (referred to as Al–Li–Co/NaBH₄) systems including Al-5 wt% Li-50 wt% nano Co, Al-7.5 wt% Li-25 wt% nano Co, Al-5 wt% Li-50 wt% micro Co, and Al-7.5 wt% Li-25 wt% micro Co had 100% hydrogen yield at 323 K. The hydrogen generation rates of these systems were regulated by Co species, Co amount, as well as consecutive runs of NaBH₄ hydrolysis. The underlying activation mechanism, including the formation of Al_0.94Co_1.06 alloy and highly active and stable Co-based catalyst has been elaborated in this study. Experimental data present an inexpensive and highly efficient hydrogen source for portable fuel cell.     

Metal nanoparticle-embedded super porous poly(3-sulfopropyl methacrylate) cryogel for H2 production from chemical hydride hydrolysis

Poly(3-sulfopropyl methacrylate) (p(SPM)) cryogel was prepared under cryogenic conditions (T = −18 °C) and used as template for in situ metal nanoparticle preparation of Co, Ni and Cu. These metal nanoparticle-containing super macroporous cryogel composites were tested for H₂ production from hydrolysis of sodium borohydride (NaBH₄) and ammonia borane (AB). It was found that amongst p(SPM)-M (M: Co, Ni, and Cu) composite catalyst systems, the catalytic performances of Co- and Ni-containing p(SPM) cryogel composite catalyst systems were the same, however in hydrolysis of NH₃BH₃, the order of performance of the catalysts was Co > Ni > Cu. Interestingly, p(SPM)-Co cryogel composite demonstrated better catalytic performances in salt environments e.g., faster H₂ production rate in sea and tap water compared to DI water, and almost no effect of ionic strength of the solution medium was observed, but the salt types were found to affect the H₂ generation rate. Other parameters that affect H₂ production rate such as metal type, temperature, water source, salt concentration, amount of metal nanocatalyst and reusability were investigated. It was found that the hydrogen generation rate (HGR) was increased to 2836 ± 90 from 1000 ± 53 (ml H₂)(g of Co min)⁻¹ by multiple loading and reduction cycles of Co catalyst. Also, it was found that TOF values are highly temperature dependent, and increased to 15.1 ± 0.8 from 2.4 ± 0.1 (mol H₂)(mol catalyst min)⁻¹ by increasing the temperature from 30 to 70 °C. The activation energy, activation enthalpy and activation entropy were determined as 40.8 kJ (mol)⁻¹, 37.23 kJ (mol K)⁻¹, and −170.87 J (mol K)⁻¹, respectively, for the hydrolysis reaction of NaBH₄ with p(SPM)-Co catalyst system, and 25.03 kJ (mol)⁻¹, 22.41 kJ (mol K)⁻¹, and −182.8 J (mol K)⁻¹, respectively, for AB hydrolysis catalyzed by p(SPM)-Co composite system.     

A study on hydrogen generation from NaBH4 solution using Co-loaded resin catalysts

Hydrogen production via chemical processes has gained great attention in recent years. In this study, Co-based complex catalyst obtained by adsorption of Co metal to Amberlite IRC-748 resin and Diaion CR11 were tested for hydrogen production from alkaline NaBH₄ via hydrolysis process. Their catalytic activity and microstructure were investigated. Process parameters affecting the catalytic activity, such as NaOH concentration, Co percentage and catalyst amount, as well as NaBH₄ concentration and temperature were investigated. Furthermore, characteristics of these catalysts were carried out via SEM, XRD and FT-IR analysis. Hydrogen production rates equal to 211 and 221 ml min⁻¹ g_cat⁻¹ could be obtained with Amberlite IRC-748 resin and Diaion CR11 Co based complex catalysts, respectively. The activation energies of the catalytic hydrolysis reaction of NaBH₄ were calculated as 46.9 and 59.42 kJ mol⁻¹ for Amberlite IRC-748 resin and Diaion CR11 based catalysts respectively kJ mol⁻¹ from the system consisting of 3% Co, 10 wt% NaBH₄ and 7 wt% NaOH as well as 50 mg catalyst dosage. It can be concluded that Co-based resins as catalysts for hydrogen production is an effective alternative to other catalysts having higher rate.     

Silica embedded cobalt(0) nanoclusters: Efficient, stable and cost effective catalyst for hydrogen generation from the hydrolysis of ammonia borane

Cobalt(0) nanoclusters embedded in silica (Co@SiO₂) were prepared by a facile two-step procedure. In the first step, the hydrogenphosphate anion (HPO₄²⁻) stabilized cobalt(0) nanoclusters were in situ generated from the reduction of cobalt(II) chloride during the hydrolysis of sodium borohydride (NaBH₄) in the presence of stabilizer. Next, HPO₄²⁻ anion-stabilized cobalt(0) nanoclusters were embedded in silica formed by in situ hydrolysis and condensation of tetraethylorthosilicate added as ethanol solution. Co@SiO₂ can be separated from the solution by vacuum filtration and characterized by UV-Vis electronic absorption spectroscopy, TEM, SEM-EDX, ATR-IR and ICP-OES techniques. Co@SiO₂ are found to be highly active and stable catalysts in the hydrolysis of ammonia borane (AB) even at low cobalt concentration and room temperature. They provide an initial turnover frequency of 13.3 min⁻¹ and 24,400 total turnovers over 52 h in the hydrolysis of AB at 25.0 ± 0.5 °C. Moreover, Co@SiO₂ retain 72% and 74% of the initial activity after ten runs recyclability and five cycles reusability test in the hydrolysis of AB, respectively. The kinetics of hydrogen generation from the hydrolysis of AB catalyzed by Co@SiO₂ was studied depending on the catalyst concentration, substrate concentration, and temperature. The activation parameters of this catalytic reaction were also determined from the evaluation of the kinetic data.     

Steam reforming of iso-octane toward hydrogen production over mono- and bi-metallic Cu–Co/CeO2 catalysts: Structure-activity correlations

Τhe feasibility of tailoring the iso-octane steam reforming activity of Cu/CeO₂ catalysts through the use of Co as a second active metal (Cu_20−xCo_x, where x = 0, 5, 10, 15, 20 wt%), is investigated. Characterization studies, involving N₂ adsorption–desorption at −196 °C (BET), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and Temperature Programmed Reduction (H₂-TPR), were carried out to reveal the impact of the morphological, structural and surface properties of the catalysts on the reforming performance. The results showed that reforming activity was monotonically increased upon increasing cobalt loading. The Co/CeO₂ catalyst demonstrated the optimum performance with a H₂ yield of 70–80% in the 600–800 °C temperature interval. The Co/CeO₂ catalyst exhibited also excellent stability at temperatures above 700 °C, while Cu-based catalysts rapidly deactivated in long term stability tests. A close correlation between surface/redox properties and steam reforming efficiency was established. The lower reducibility of Co/CeO₂ catalysts, associated with the formation of Co³⁺ species, in Co₃O₄-like phase, can be accounted for the enhanced carbon tolerance of Co-based catalysts. Furthermore, the high concentration of surface oxygen species on Co/CeO₂ catalysts can be considered for their enhanced performance. On the other hand, the Cu-induced easier reducibility of bimetallic catalysts, in conjunction with carbon deposition and active phase sintering can be accounted for their inferior steam reforming performance. Irreversible changes in the redox properties of Cu-based catalysts, taking place under reaction conditions, could be resulted to ceria deactivation thus hindering the redox process to keep on.     

Copper promoted Co/MgO: A stable and efficient catalyst for glycerol steam reforming

Different types of cobalt-based mixed oxide catalysts (20 wt%Co/MgO, 5 wt%Cu-20 wt% Co/MgO, 20 wt%Co/50%MgO–50%Al₂O₃) were synthesized by the co-precipitation method and applied for hydrogen production from glycerol steam reforming. The catalysts were characterized using X-ray diffraction (XRD), H₂-Temperature-programmed reduction (H₂-TPR), CO₂-Temperature Programmed desorption, CO-Chemisorption, and CHN techniques. The H₂-TPR analysis showed the reducibility of cobalt-oxide (5Cu20CM; 5 wt%Cu-20 wt% Co/MgO) was enhanced by the copper, and reduction profiles of cobalt oxide shifted to a lower temperature (<450 °C). Among the catalysts, 5Cu20CM showed a maximum yield of hydrogen (74.6%) with 100% conversion of glycerol to the gaseous phase. The superior catalytic performance of 5Cu20CM for glycerol conversion was attributed to the smaller particle size (7 nm), higher dispersion of cobalt (35.0%), and the higher surface area (56 m²/g) of cobalt metal. Furthermore, Raman spectroscopy of the spent catalysts confirmed that the copper promoted cobalt-magnesium catalyst suppressed the carbon formation, consequently, 5Cu20CM catalyst showed a stable performance up to 30 h.     

Hydrogen production from ammonia borane via hydrogel template synthesized Cu, Ni, Co composites

In situ Co, Cu and Ni nanoparticles were synthesized by chemical reduction of the absorbed Co (II), Cu (II) and Ni (II) ions inside hydrogel networks prepared from 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS) and were used as a catalyst system in the generation of hydrogen in hydrolysis of ammonia borane (AB). Several parameters affecting the hydrolysis reaction such as the type of the metal, the amount of catalyst, the initial concentration of AB, and temperature, were investigated. The activation energy values in the hydrolysis reaction of AB solution in the presence p(AMPS)-Co, p(AMPS)-Cu and p(AMPS)-Ni catalyst systems were calculated as E_a = 47.7 kJ mol⁻¹, 48.8 kJ mol⁻¹ and 52.8 kJ mol⁻¹, respectively. Thus, the catalytic activity of the metal nanoparticles prepared inside the same hydrogel matrix was found to be Ni < Cu < Co.     

Bacterial cellulose derived carbon as a support for catalytically active Co–B alloy for hydrolysis of sodium borohydride

The fast release of hydrogen from borohydride is highly desired for a fuel cell system. However, the generation of hydrogen from borohydride is limited by the low activity and low stability of the catalyst. Herein, a highly active catalyst is synthesized through a simple one-step chemical reduction using bacterial cellulose (BC) derived carbon as a support for the active Co–B alloy. The morphology and microstructure of the BC/Co–B nanocomposite are characterized by SEM, TEM, XRD, and BET adsorption analysis. The BC/Co–B possesses high surface area (125.31 m² g^?1) high stability and excellent catalytic activity for the hydrolysis of NaBH₄. Compared with unsupported Co–B nanocomposite or commercial carbon supported Co–B, the BC/Co–B nanocomposite shows greatly improved catalytic activity for the hydrolysis of NaBH₄ with a high hydrogen generation rate of 3887.1 mL min^?1 g^?1 at 30 °C. An activation energy of 56.37 kJ mol^?1 was achieved for the hydrolysis reaction. Furthermore, the BC/Co–B demonstrated excellent stability. These results indicate that the BC/Co–B nanocomposite is a promising candidate for the hydrolysis of borohydrides.     

Co–B nanoparticles supported on carbon film synthesized by pulsed laser deposition for hydrolysis of ammonia borane

Thin films of Carbon-supported Co–B nanoparticles were synthesized by using Pulsed Laser Deposition (PLD) and used as catalysts in the hydrolysis of Ammonia Borane (AB) to produce molecular hydrogen. Amorphous Co–B-based catalyst powders, produced by chemical reduction of cobalt salts, were used as target material for nanoparticles-assembled Co–B film catalysts preparation through PLD. Various Ar pressures (10–50 Pa) were used during deposition of carbon films to obtain extremely irregular and porous carbon support with high surface area prior to Co–B film deposition. Surface morphology of the catalyst films was studied using Scanning Electron Microscopy, while structural characterization was carried out using X-Ray diffraction. The hydrogen generation rate attained by carbon-supported Co–B catalyst film is significantly higher as compared to unsupported Co–B film and conventional Co–B powder. Almost complete conversion (95%) of AB was obtained at room temperature by using present film catalyst. Morphological analysis showed that the Co–B nanoparticles produced after the laser ablation process act as active catalytic centers for hydrolysis while the carbon support provides high initial surface area for the Co–B nanoparticles with better dispersion and tolerance against aggregation. The efficient nature of our carbon-supported Co–B film is well supported by the obtained very low activation energy (∼29 kJ (mol)⁻¹) and exceptionally high H₂ generation rate (13.5 L H₂ min⁻¹ (g of Co)⁻¹) by the hydrolysis of AB.