Highly active heteropolyanions supported Co catalysts for fast hydrogen generation in NaBH4 hydrolysis

This paper reports on the use of Co supported catalyst for the hydrolysis of NaBH₄. Various materials with different acid/base surface properties have been chosen as supports (hydrotalcites, KF/Al₂O₃, heteropolyanions). The supports and the Co-containing catalysts were characterized by X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma, nitrogen adsorption. The NaBH₄ hydrolysis reaction was studied in a liquid phase calorimeter coupled with a gas counter in order to follow at the same time the kinetics and the heat of reaction. Co supported on heteropolyanions showed great results in terms of reaction rate. Cobalt dispersed on heteropolyanions is a real promising catalytic system for the development of hydrogen generation in PEM fuel cells for portable devices.     

Controllable hydrogen production from NaBH4 hydrolysis promoted by acetic acid

Numerous catalysts have been widely investigated for accelerating hydrogen production from NaBH₄ hydrolysis. However, these catalysts are usually complicated in structures, costly in fabrication, and hazardous for environment. In this work, cheap and environment-friendly acetic acid, CH₃COOH, is employed to promote NaBH₄ hydrolysis to produce hydrogen in a considerable rate. The experimental results demonstrate that the addition of suitable amount of CH₃COOH into NaBH₄ solutions stabilized with NaOH could dramatically accelerate the hydrolysis reaction. Additionally, the start/stop of NaBH₄ hydrolysis could be controlled by adding acid or base into the solution to realize “go-as-you-please” on-site hydrogen production.     

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.     

Multilevel N-doped carbon nanotube/graphene supported cobalt phosphide nanoparticles for electrocatalytic hydrogen evolution reaction

Electrochemical water splitting plays an important role in alternative energy studies, since it is highly efficient and environment-friendly. Accordingly, it is an ideal way of providing alternative to meet the urgent need of finding sustainable and clean energy. This study presents the fabrication of CoP attached on multilevel N-doped CNT/graphene (CoP–CNT/NG) hybrids. The multilevel carbon structure can enhance electrical conductivity efficiently and increase the reaction active area immensely. The obtained electrocatalyst exhibits great electronic conductivity (17.8 s cm⁻¹) and HER activity with low overpotential (155 mV at 10 mA cm⁻²), low Tafel slope (69.1 mV dec⁻¹) in 0.5 M H₂SO₄. In addition, the CoP–CNT/NG displays prominent electrochemical durability after 18 h.     

Cost-effective synthesis of carbon loaded Co3O4 for controlled hydrogen generation via NaBH4 hydrolysis

The simple, reliable, and economical process of combustion is used to synthesize carbon loaded cobalt oxide (C–Co₃O₄) for hydrogen generation via NaBH₄ hydrolysis. The effect of NaBH₄ concentration, pH, and temperature of the solution on hydrogen generation is investigated in detail. C–Co₃O₄ exhibits zero order reaction kinetics with respect to NaBH₄ concentration. A stable Hydrogen Generation Rate (HGR) is observed throughout the reaction in the temperature range of 300–315 K using C–Co₃O₄. It is found that 0.01 g of C–Co₃O₄ exhibited high reaction activity with a maximum HGR of 5430 ml min^?1 g^?1 for the optimal solution at 320 K. The activation energy is calculated to be 55.9 kJ mol^?1 for hydrolysis of NaBH₄ using C–Co₃O₄. The present study provides an economical method for the large-scale production of C–Co₃O₄ for hydrogen generation from NaBH₄ hydrolysis, which can pave the way to commercialize hydrogen as a main source of fuel.     

Fly ash as catalyst support material in the hydrolysis of ethylenediamine bisborane for hydrogen production: The use of coal-fired power plant waste

Efficient, low-cost and safe new systems are still needed for the storage and usage of hydrogen energy, which is considered the most important energy source of the future. For this reason, the aim of this study was to prepare Co⁰, Ni⁰, and Cu⁰ composite catalysts with fly ash (FA) formed by combustion of coal in thermal power plants to be used for the dehydrogenation of ethylenediamine bisborane (EDAB) as a hydrogen source. In the hydrolysis reactions of EDAB, parameters such as metal type, catalyst concentration, temperature, and EDAB concentration were investigated. The FA-Cu⁰ composite catalyst was determined to be an effective catalyst system for hydrogen production by hydrolysis of EDAB from among the FA-M⁰ composite catalysts. Besides, FA can be used as an effective support material in order to prevent agglomeration of metal particles.     

Magnetic dendritic KCC-1 nanosphere-supported cobalt composite as a separable catalyst for hydrogen generation from NaBH4 hydrolysis

The introduction of magnetism into a catalyst can greatly optimize its separation performance. In the present work, a kind of magnetically separable catalysts for promoting NaBH₄ hydrolysis have been fabricated by anchoring cobalt nanoparticles on magnetic dendritic KCC-1 nanospheres composed of magnetic Fe₃O₄ core and fibrous shell. The fabricated catalysts were characterized with various characterization methods, including absorption spectroscopy (AAS), scanning electron microscopy (SEM), high-resolution transmission electronic microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), and Fourier transform infrared (FT-IR), etc. This kind of catalysts exhibit high catalytic activity for promoting the hydrolysis of NaBH₄ under alkaline conditions, giving a hydrogen generation rate and activation energy of 3.83 L min⁻¹ g_Co⁻¹ (30 °C) and 53.63 kJ mol⁻¹, respectively. After used for 5 cycles, the catalyst showed 36.5% catalytic activity reserved. Most importantly, the magnetism of the catalyst made it easily separated and recycled from the solution after the reaction completed. The development of this kind of catalysts could provide a promising option for catalyzing NaBH₄ hydrolysis for portable hydrogen production from.     

Synthesis of cobalt-doped catalyst for NaBH4 hydrolysis using eggshell biowaste

In the present study, a cobalt-doped catalyst was prepared from chicken eggshell powder (CEP) biowaste to be used in the hydrolysis of sodium borohydride (NaBH₄). In the presence of the prepared catalyst (CEP_cat), possible effects of the parameters of NaOH concentration (%), catalyst amount (g), NaBH₄ concentration (%), process temperature (^oC) and reusability affecting the hydrolysis of sodium borohydride were examined. The CEP_cat obtained was characterized with FT-IR, TGA, XRD, SEM and EDX analyses. The hydrogen generation rate (HGR) was determined as 432 mL g_Co⁻¹ min⁻¹ in the presence of 1 g CEP_cat, a CoO/CaO ratio of 10/90 and 1% NaBH₄ concentration. The activation energy of the NaBH₄ hydrolysis reaction was calculated as 16.78 kJ mol⁻¹. After 16 reuses of the CEP_cat there was no significant decrease in the hydrogen volume. Compared to the first use while there was an increase in the HGR. These results showed that the CEP_cat prepared has a significant advantage over other catalysts for use in NaBH₄ hydrolysis.     

Ceria supported manganese(0) nanoparticle catalysts for hydrogen generation from the hydrolysis of sodium borohydride

Herein we report for the first time the preparation and catalytic use of the ceria supported manganese(0) nanoparticles in hydrogen generation from the hydrolysis of sodium borohydride. They are in situ formed from the reduction of manganese(II) ions on the surface of ceria nanopowders during the catalytic hydrolysis of sodium borohydride in aqueous solution at room temperature. Manganese(0) nanoparticles are isolated from the reaction solution by centrifugation and characterized by a combination of analytical techniques. Nanoceria supported manganese(0) nanoparticles are highly active and long-lived catalysts providing a turnover frequency of 417 h^?1 and 45,000 turnovers in hydrogen generation from the hydrolysis of sodium borohydride at 25.0 ± 0.1 °C. They also have high durability as they retain 55% of their initial catalytic activity after the fifth cycle of hydrolysis providing a release of 4 equivalent H₂ gas per mol of sodium borohydride. The noticeable activity loss in successive runs of hydrolysis is attributed to the deactivation due to agglomeration. High activity and stability of ceria supported manganese(0) nanoparticles are ascribed to the unique nature of reducible cerium oxide. The formation of cerium(III) defects under catalytic conditions provides strong binding for the manganese(0) nanoparticles to oxide surface which makes the catalytic activity and stability favorable. Our report also includes the results of kinetic study of catalytic hydrolysis of sodium borohydride depending on the temperature, catalyst and substrate concentration.     

Sustainable hydrogen production via LiH hydrolysis for unmanned air vehicle (UAV) applications

In the current study, an experimental approach for the further understanding of the LiH hydrolysis reaction for hydrogen production is considered. The experimental work has been undertaken under small scale conditions by utilising fixed bed reactors. The hydrolysis reaction has been studied at several oven temperatures (150 °C, 300 °C and 500 °C). The favourable driving potentials for the hydrolysis reactions were identified by the utilisation of the Gibbs free energy analysis. The main outcome of the study is the deceleration of the reaction pace due to the formation of the by-product layers during the reaction. At the initial stage, due to the contact of steam with the unreacted and fresh LiH surface, the reaction proceeds on a fast pace, while the formation of the layers tends to decelerate the diffusion of steam into the core of material, forcing the production step to be slower. The hydrogen yield was found to be more than 90% of the theoretical value for all the reaction temperatures. Finally, a scenario of a hybrid-electric propulsion system for Unmanned Aerial Vehicles (UAVs) including Li-ion battery, Proton Membrane Fuel Cell (PEMFC) and an on-board hydrogen production system based on LiH hydrolysis is introduced and studied.     

Biogas reforming for hydrogen production over nickel and cobalt bimetallic catalysts

Ni/Co bimetallic catalysts supported by commercial γ-Al₂O₃ modified with La₂O₃ for biogas reforming were prepared by conventional incipient wetness impregnation. The catalysts were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area and porosity analysis (BET), H₂ temperature-programmed reduction (H₂-TPR), transmission electron microscopy (TEM) and thermogravimetry coupled to differential scanning calorimetry (TG–DSC). XRD and XPS analysis revealed that a Ni/Co alloy was formed in the bimetallic catalysts. The Ni/Co ratio could be adjusted to improve pore textural properties, which enhanced the metal particle dispersion and resulted in smaller metal particle size, and thus increased the catalytic activity and resistance to carbon deposition. The activity and stability of the catalysts for biogas reforming was tested at 800 °C, ambient pressure, GHSV of 6000 ml g_cat⁻¹ h⁻¹ and a CH₄/CO₂ molar ratio of 1 without dilute gas. Experimental results showed that the catalytic activity could be closely related to the Ni/Co ratio. The bimetallic catalyst 7Ni3Co/LaAl exhibited better catalytic and anti-coking performance due to smaller metal particles, higher metal dispersion, uniform pore distribution, surface enrichment of Co, as well as the synergetic effect between Ni and Co. During a 290 h stability test over the catalyst 7Ni3Co/LaAl, the average conversion of CH₄ and CO₂, selectivity to H₂ and CO, and ratio of H₂/CO were 93.7%, 94.0%, 94.9%, 97.8%, and 0.97, respectively. The average coking rate was 0.0946 mg g_cat⁻¹ h⁻¹.     

Efficient hydrogen production from ammonia borane hydrolysis catalyzed by TiO2-supported RuCo catalysts

Hydrolysis of ammonia borane provides a reliable pathway for hydrogen production, while suitable catalysts are indispensable to make the hydrolysis reaction reach a considerable rate. In the present work, a series of TiO₂-supported RuCo catalysts have been fabricated by coprecipitation and subsequent reduction of Ru³⁺ and Co²⁺ on the surface of TiO₂ nanoparticles. Transmission electron microscopy and elemental mapping have verified the good distribution of metal species in the catalysts. The fabricated catalysts have shown excellent performance for catalyzing ammonia borane hydrolysis, especially in alkaline solutions with 0.5 M NaOH. For Ru₁Co₉/TiO₂ in which Ru/Co molar ratio is 1:9, the active energy of catalyzed ammonia borane hydrolysis is 33.25 kJ/mol, and a turnover frequency based on Ru as high as 1408 mol_H2/(mol_Ru·min) is obtained at 25 °C. Moreover, when different types of TiO₂ substrates are used, anatase TiO₂-supported catalysts show better catalytic activity than their counterparts with rutile TiO₂ as substrate or mixture of anatase and rutile TiO₂ as substrate.     

PVP-stabilized platinum nanoparticles supported on modified silica spheres as efficient catalysts for hydrogen generation from hydrolysis of ammonia borane

Ammonia borane (AB) is considered to be a promising solid hydrogen carrier. In this work, poly(N-vinyl-2-pyrrolidone) (PVP)-protected platinum nanoparticles are supported on γ-methacryloxypropyltrimethoxysilane (γ-MPS) modified silica spheres (Pt-PVP/SiO₂(M)), which are firstly used as highly efficient catalysts for hydrolysis of AB. Platinum nanoparticles possess a tiny size of 2–3 nm and are uniformly dispersed over modified silica spheres. Pt-PVP/SiO₂(M) catalysts with a Pt loading amount of 1.30 wt% show the highest catalytic activity with a turnover frequency (TOF) value of 371 mol_H2 mol_Pt^?1 min^?1 (866 mol_H2 mol_Pt^?1 min^?1 corrected for the surface atoms) at 25 °C. The activation energy is calculated to be 46.2 kJ/mol. Furthermore, owing to the synergistic effect between the modifier of silica spheres and the capping agent of metal nanoparticles, Pt-PVP/SiO₂(M) catalysts have a higher loading amount (8.7 and 6.5 times) and TOF value (4.8 and 5.5 times) than the counterparts prepared without γ-MPS and PVP, respectively.     

Kinetics of boron hydrolysis for hydrogen production

This study examines the kinetics of boron hydrolysis. The boron hydrolysis reaction is classified as a noncatalytic heterogeneous reaction. It was found the steam rapidly hydrolyzes the boron, forming an oxide ash layer that then also reacts with the steam, forms gaseous boric acid, and re-exposes the boron substrate to steam. Additionally, the thickness of the ash layer, once formed, was found to be relatively constant through the reaction. In order to facilitate kinetic analysis the reaction was divided into two stages: a fast oxidation stage and a second, slower stage. The corresponding kinetic parameter for the first stage activation energy is 25 kJ/mol. The shrinking core model was used to model the second stage of the hydrolysis reaction where it was found that diffusion of steam through the ash layer was the rate limiting step.     

CeO2 supported multimetallic nano materials as an efficient catalyst for hydrogen generation from the hydrolysis of NaBH4

Nowadays, there is still no suitable method to store large amounts of energy. Hydrogen can be stored physically in carbon nanotubes or chemically in the form of hydride. In this study, sodium borohydride (NaBH₄) was used as the source of hydrogen. However, an inexpensive and useful catalyst (Co–Cr–B/CeO₂) was synthesized using the NaBH₄ reduction method and its property was characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), x-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) measurements. The optimized Co–Cr–B/CeO₂ catalyst exhibited an excellent hydrogen generation rate (9182 mLg_metal⁻¹min⁻¹) and low activation energy (35.52 kJ mol⁻¹). The strong catalytic performance of the Co–Cr–B/CeO₂ catalyst is thought to be based on the synergistic effect between multimetallic nanoparticles and the effective charge transfer interactions between the metal and the support material.     

Effect of preparation methods on the catalyst performance of Co/MgLa mixed oxide catalyst for COx-free hydrogen production by ammonia decomposition

This work deals with the effect of catalyst preparation method of the mixed Co, Mg and La oxide catalysts on their structure and catalytic properties for ammonia decomposition. Two methods are used for catalysts preparations impregnation and co-precipitation (in air and in pure O₂ atmosphere), The Mg/La = 2 molar ratio and 5 wt% of cobalt content was maintained same in all catalysts. The catalyst performance was evaluated in the temperature range 300–550 °C at atmospheric pressure. The prepared catalysts were characterized by BET, XRD, TPR, XPS, CO₂-TPD and SEM techniques. No pronounced differences were observed in BET among the catalysts. It was found that the 5CML-OXY (5 wt%Co over MgLa catalyst prepared by co-precipitation method in oxygen atmosphere) has superior activity among the other catalysts. This could be attributed to availability of easily reducible cobalt species determined by TPR studies and enhanced interaction between Mg and La determined by SEM and XPS. The moderate basic site density determined by CO₂-TPD results was also increased in 5CML–OXY catalysts compared with other catalysts. These consequences are might be one of the reasons for enhanced activity of 5CML–OXY catalyst compared to other catalysts. Hence catalyst preparation by co-precipitation in oxygen atmosphere is the best method which might be one of the parameters that influenced on catalytic properties of the cobalt on MgOLa₂O₃ system, for ammonia decomposition.     

Photocatalytic hydrogen production from water/methanol solutions over highly ordered Ag-SrTiO3 nanotube arrays

The highly ordered Ag-SrTiO₃ nanotube arrays (NTAs) with uniform size were successfully synthesized by a combination of anodic oxidation, hydrothermal process and photocatalytic reduction method. X-ray photoelectron spectroscopy analysis reveals that Ag exists in the form of metallic silver, which is in good agreement with the X-ray diffraction characterization. Moreover, the UV-vis diffuse reflectance spectra indicate that Ag-SrTiO₃ NTAs have a strong absorption in the visible region which is attributed to the plasmon resonance of silver nanoparticles. After Ag loading, a further improvement of the photocatalytic activity for hydrogen production was obtained. Based on the above results, a possible electron-hole transfer mechanism was also assumed.     

COx-free hydrogen production from ammonia on novel cobalt catalysts supported on 1D titanate nanotubes

Hydrogen storage in chemical bonds such as ammonia is an attractive alternative to physical hydrogen storage if a sustainable and efficient catalyst can be designed for the release of COx-free hydrogen on demand. This paper presents a systematic study for the design of cobalt-based catalysts, moving away from scare Ru-based systems. It demonstrates the importance of the preparation method of cobalt-based catalysts not only to tune the size of the active species and their interaction with the support but also in the promotion of active species. Cobalt supported on titanate nanotubes via an ion-exchange method leads to the incorporation of the cobalt into the crystal structure of the titanates facilitating the formation of unreducible cobalt titanate species with a detrimental effect on the reactivity, and the thermal stability of the titanate support. Considerably higher reactivities can be achieved by loading cobalt via deposition-precipitation with NaOH method, leading to the formation of reducible cobalt particles on the surface of the titanate nanorods support. In this case, the rate of reaction is inversely related to the cobalt particle size, pointing out the key effect of particle size of cobalt-based catalyst for the hydrogen production in ammonia decomposition. Although the activities reported here for cobalt-based catalysts are still below those of the state-of-the-art ruthenium counterpart systems, this work provides unique insights for the future development of sustainable catalysts for the use of ammonia as hydrogen vector.     

Nickel catalysts obtained from hydrotalcites by coprecipitation and urea hydrolysis for hydrogen production

Nickel hydrotalcites were subjected to synthesis using two methods: coprecipitation and urea hydrolysis. The thermal decomposition of the hydrotalcite precursors produced mixed oxides corresponding to the active phases or final catalysts.     

PDMA cryogel beads as a catalyst for hydrogen generation from NaBH4 alcoholysis

Poly[2-(dimethylamino)ethyl methacrylate] cryogel beads were prepared under cryogenic conditions via free radical polymerization and used as a catalyst in the production hydrogen (H₂) from NaBH₄ by alcoholysis. The efficiency of the catalyst was investigated in the range of 0–40 °C by both methanolysis and ethylene glycolysis reactions, and its reuse was tested. Accordingly, it was observed that the methanolysis reaction was faster than the ethylene glycolysis reaction. When the hydrogen generation rate (HGR) values between 0 and 40 °C were compared, it was concluded that the methanolysis reaction rate increased from 1550 to 4800 mL.min⁻¹g⁻¹ and the ethylene glycolysis reaction rate increased from 923 to 3551 mL.min⁻¹g⁻¹. In the alcoholysis reaction catalyzed by PDMA cryogel beads, the activation energy was calculated as 19.34 and 22.77 kJ.mol⁻¹ for the methanolysis and ethylene glycolysis reactions, respectively. After six repetitions, the catalyst activity was calculated over 50% for NaBH₄ methanolysis and ethylene glycolysis.