Boron-doped Cobalt nanoparticles anchored to different activated carbon supports as recyclable catalysts for enhanced alkyl-substituted amine boranes dehydrogenation

Aiming at easily recoverable and regenerated catalyst development for efficient hydrogen production from alkyl-substituted amine boranes, boron (B)-doped cobalt (Co) nanoparticles with similar composition and particle size were anchored on two different activated carbon supports: granule and pellet. The effect of different independent variables such as type active carbon support (granule or pellet), alkyl-substituted amine boranes (ammonia borane-AB, methyl amine borane-MEAB and ethylenediamine borane-EDAB), recyclability cycle on hydrogen generation rate as dependent variable were investigated via Analysis of Variance (ANOVA). In addition, compared with ammonia borane, alkyl-substituted ones showed slower hydrogen generation properties in presence catalysts: AB > MEAB > EDAB. Among B-doped Co catalysts supported with different activated carbon supports, granule type activated carbon supported one showed best catalytic performance of derivatives of borane compounds dehydrogenation, and the hydrogen generation rate (2.49–0.44 L H₂ min^?1 g^?1_Co) and TOF values (7338.52–1451.96 mol_H2 mol^?1_catmin^?1). In the bargain, granule catalysts performed good recyclability activity, maintains its high hydrogen yields and its activity only decreased % 71 even after 5 repetitive cycles.     

One-pot synthesis of supported Ni@Al2O3 catalysts with uniform small-sized Ni for hydrogen generation via ammonia decomposition

Nickel based materials are the most potential catalysts for CO_x-free hydrogen production from ammonia decomposition. However, the facile synthesis of supported Ni-based catalysts with small size Ni particles, high porosity and good structural stability is still of great demand. In this work, uniform small-sized Ni particles supported into porous alumina matrix (Ni@Al₂O₃) are synthesized by a simple one-pot method and used for ammonia decomposition. The Ni content is controlled from 5 at.% to 25 at.%. Especailly, the 25Ni@Al₂O₃ catalyst shows the best catalytic performance. With a GHSV of 24,000 cm³g_cat^?1h^?1, 93.9% NH₃ conversion is achieved at 600 °C and nearly full conversion of NH₃ is realized at 650 °C. The hydrogen formation rate of 25NiAl catalyst reaches 3.6 mmol g_cat^?1min^?1 at 400 °C and 7.8 mmol g_cat^?1min^?1 at 450 °C. The enhanced activity observed on 25Ni@Al₂O₃ catalyst can be attributed to the structural characteristic that large amounts of uniform-sized small (7.2 ± 0.9 nm) Ni particles are highly dispersed into porous alumina matrix. The aggregation of active metallic Ni particles during the high temperature reaction can be effectively prevented by the porous alumina matrix due to the strong interaction between them, thus ensuring a good catalytic performance.     

Ru-Ba/ANF catalysts for ammonia decomposition: Support carbonization influence

The study of ruthenium catalysts for ammonia decomposition on carbonized and non-carbonized Al₂O₃ nanofibers (ANF) showed that the activity of catalysts with carbonized supports (ANFC) was 2–3 times higher compared to non-carbonized ones. Thus, on Ru/ANFC and Ru/ANF the release of hydrogen reached 133.5 and 34.7 mmol H₂/(min·g_cat), respectively, whereas on Ru-Ba^Ac/ANFC and Ru-Ba^Ac/ANF, only 118.8 and 58.6 mmol H₂/(min·g_cat), respectively. On the average, the activation energy of ammonia decomposition on ANFC-supported catalysts is 15 kJ/mol lower than that value for ANF-supported catalysts. According to TEM data, Ru particles on ANFC are larger than on ANF, but are more evenly distributed. An increase in the activity of the catalyst correlates with a change in the electronic state of the active component. XPS data for Ru indicate a shift in the binding energy towards lower values when going from ANF to ANFC.     

Bimetallic NixCo10-x/CeO2 as highly active catalysts to enhance mid-temperature ammonia decomposition: Kinetics and synergies

Catalytic ammonia decomposition is an attractive method to generate hydrogen at mid-temperatures (<700 °C) but must incorporate precious metals (Pd, Ru, etc.) to ensure high reactivity. Developing Ni-based catalysts to decompose ammonia can enhance its prospect for hydrogen generation. However, the catalytic activity of Ni is hardly satisfactory at mid-temperatures. In this work, we show the bimetallic Ni_xCo_10-x/CeO₂ towards mid-temperature NH₃ decomposition, with the metal loading of Ni and Co tuned. Kinetics study demonstrates that the NH₃ decomposition reaction follows the Temkin Pyzhev mechanism and the synergy between Ni and Co can decrease the reaction orders regarding NH₃ and increase the reaction orders regarding H₂. Mechanistic results indicate that the recombinative N desorption limits the reaction rate. The synergy between Ni and Co can simultaneously decrease the energy barriers of the recombinative N desorption and mitigate the H₂ poisoning effect. Therefore, Ni_7.5Co_2.5/CeO₂ displays both high ammonia conversion (96.96%) and hydrogen formation rate (1947.9 mmol/(g_cat.h)) at 650 °C. We hope the mechanism in this work can be used to guide the design of inexpensive catalysts to decompose ammonia at mid-temperatures.     

A review on the catalysts used for hydrogen production from ammonia borane

Boron compounds have recently attracted attention in hydrogen production since they contain many hydrogen atoms. Among these compounds, ammonia borane, which has high hydrogen density (in weight basis), can be used to produce hydrogen through a hydrolysis reaction. However, since the ammonia borane solution is highly resistant to hydrolysis under ambient conditions, there is a need for active and stable catalysts to accelerate the reaction. In this review paper, unsupported and carbon-based supported metal catalysts used for hydrogen production through the hydrolysis of ammonia borane are presented. Noble metal catalysts (Ru, Rh, Pd, Pt and their binary and ternary alloys) and non-noble metal catalysts (Co, Ni, Fe, Cu and their binary and ternary alloys) were examined. The activation energy of reaction and turnover frequency (TOF) values were compared for these catalysts. Among the unsupported catalysts, it was concluded that the multi-metal catalyst systems (binary, ternary and quaternary) have higher catalytic activity than a single use of the same metals. In addition, the comparison showed that the supported catalysts are more resistant to catalytic cycles and suitable for long-term use. It was observed that CNT supported Rh (TOF = 706 mol H₂ mol cat⁻¹ min⁻¹) and graphene supported Ru (TOF = 600 mol H₂ mol cat⁻¹ min⁻¹) catalysts are the most active catalysts for the hydrogen generation from the ammonia borane at room temperature.     

Graphite carbon nitride loaded nitrogen-doped carbon and cobalt nanoparticles ternary photocatalyst for enhanced solar-driven hydrogen evolution

In this paper, we designed a composite photocatalytic system in which cobalt nanoparticles (Co NPs) are attached to nitrogen-doped carbon (N-d-C) and co-bonded to the surface of the noted photocatalyst graphite carbon nitride (g-C₃N₄), showing an excellent photocatalytic hydrogen production. The bulk g-C₃N₄ was formed in the first thermal treatment in air using melamine as a precursor. Subsequently, the secondary calcination under N₂ led to the synchronous fabrication of N-d-C/Co NPs and their combination with g-C₃N₄ to form a novel ternary photocatalyst (g-C₃N₄/N-d-C/Co NPs). Co NPs exposed on the surface of the nanomaterials endowed much more reaction sites than g-C₃N₄ for photocatalytic hydrogen production. Meanwhile, the embedded N-d-C provided an additional transfer approach for photocarriers. The as-prepared composite nanomaterials own a relatively high specific surface area of 97.45 m² g^?1 with an average pore size of 3.83 nm. As a result, compared with pristine g-C₃N₄ (～25.35 μmol g^?1 h^?1), the photocatalytic performance was increased by over 10 times (～270.05 μmol g^?1 h^?1). Our work gives a novel approach for highly active g–C₃N₄–based photocatalysts in the field of photocatalysis.     

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.     

Ammonia decomposition on a highly-dispersed carbon-embedded iron catalyst derived from Fe-BTC: Stable and high performance at relatively low temperatures

Fe-BTC (iron 1,3,5-benzenetricarboxylic acid), a commercially available metal organic framework (MOF), was used as a sacrificial template to produce a series of carbon-embedded Fe catalysts upon its pyrolysis at different temperatures. The catalyst prepared by pyrolyzing Fe-BTC at 400 °C under flowing N₂ provided a high graphitic degree on the carbon support hosting highly dispersed Fe species at a Fe loading of 34 wt%. Performance measurements on ammonia decomposition to produce CO_x-free hydrogen showed that this catalyst provided an ammonia conversion of 73.8% at a space velocity of 6000 cm³ NH₃ h⁻¹ g_cat⁻¹ and at 500 °C for at least 120 h. This stable performance, exceeding that of some of the best non-noble metal catalysts, was associated with the presence of highly-dispersed Fe species at a significantly high Fe loading, embedded in a carbonaceous shell. The presence of the carbonaceous shell not only protected the active species against sintering, but also made them electron rich owing to its high level of graphitization.     

Co/CuO–NiO–Al2O3 catalyst for hydrogen generation from hydrolysis of NaBH4

This paper presents hydrogen generation measurements from the hydrolysis of NaBH₄ aqueous solutions catalyzed by Co doping on single, bimetallic and trimetallic oxide supports (Co/CuO, Co/NiO, Co/Al₂O₃, Co/NiO–Al₂O₃, Co/CuO–Al₂O_3, and Co/CuO–NiO–Al₂O₃). Support materials are synthesized by the co-precipitation method. Then, Co is doped into support materials by the impregnation method. It is found that Co/CuO–NiO–Al₂O₃ catalyst exhibited high reaction activity with a maximum hydrogen generation rate (HGR) of 2067.2 ml min^?1 g_cat^?1 at 25 °C. The effect of temperature of the solution, Co amount, and recyclability of the catalyst on hydrogen generation with Co/CuO–NiO–Al₂O₃ catalyst is investigated in detail. In addition, the highest HGR for Co/CuO–NiO–Al₂O₃ catalyst is obtained at 55 °C as 6460.0 ml min^?1 g_cat^?1. The activation energy is calculated to be 31.59 kJ mol^?1 using Co/CuO–NiO–Al₂O₃ catalyst. Co/CuO–NiO–Al₂O₃ catalyst exhibits zero-order reaction kinetics concerning NaBH₄ concentration. In addition, the Co/CuO–NiO–Al₂O₃ catalyst provided high reusability after 5 cycles.     

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.     

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.     

Fe-based catalyst derived from MgFe-LDH: Very efficient yet simply obtainable for hydrogen production via ammonia decomposition

The current study provided the first example to develop the Fe-based catalyst for CO_x-free hydrogen production via ammonia decomposition through the unique MgFe-layered double hydroxides (MgFe-LDHs) of different stoichiometric Mg/Fe ratio. The so obtained Fe-based catalyst is low-cost, readily obtainable, and environmentally friendly. Structurally, the Fe(FeN_x) species are 3D-isolated by the nano-MgO entities, improving anti-sintering potential of Fe(FeN_x); and electronically, the Fe (FeN_x) species are promoted by the nano-MgO matrix, showing the strongest promoting effect of MgO on Fe(FeN_x). At a GHSV_NH3 of 150,000 mL g_cat⁻¹ h⁻¹, the current N–Mg_5.3FeO_m catalyst can give an outstanding H₂ formation rate of 9.83 mol g_cat⁻¹ h⁻¹ at 680 °C and a TOF_H2 = 2.19 s⁻¹ at 530 °C. The influence of Mg/Fe constitution on catalyst structure, surface property, and performance was systematically investigated. The in-situ ammonia treatment was superior to the usually adopted hydrogen pre-reduction for the Fe–Mg oxide precursor, leading to easy development of small sized FeN_x specimen and activity enhancement.     

Bimetallic Pd–Bi nanocatalysts derived from NaBH4 reduction of BiOCl and Pd2+ and exhibit highly efficient hydrogen production over formaldehyde solution

Using liquid formaldehyde as a carrier to obtain clean hydrogen is a promising method. The development of inexpensive catalysts with high activity and stability is crucial for this reaction. Herein, bimetallic Pd–Bi nanocatalysts with different Pd to Bi ratios were prepared through one step in-situ reduction of BiOCl and Pd²⁺ ions by sodium borohydride (NaBH₄). The effect of Pd/Bi ratios and reaction parameters such as formaldehyde concentration and sodium hydroxide concentration on hydrogen production performance were systematically studied. By optimizing the Pd contents in Pd–Bi nanocatalysts under the optimized reaction conditions, an much higher hydrogen (H₂) production rate of 472.2 mL min^?1g^?1 over Pd/BiOCl-3% under 298.15 K can be achieved, which is 4.01 times that of pure Pd nanoparticles (NPs) and much higher than most reported metal-based catalysts.     

Polypyrrole supported Co–W–B nanoparticles as an efficient catalyst for improved hydrogen generation from hydrolysis of sodium borohydride

Effective and reusable catalysts with high performance are essentially necessary for NaBH₄ based on-demand hydrogen generators to the widespread use for energy conversion in fuel cell power systems. Herein, we report a facile synthesis of surfactant-directed polypyrrole-supported Co–W–B nanoparticles as a robust catalyst for efficient hydrolysis of NaBH₄ reaction. This non-noble metal catalyst provides much higher catalytic activity than a conventional cobalt boride catalyst. By incorporating tungsten to catalyst composition and tuning molar ratio of W/(Co + W), about a four-fold higher hydrogen generation rate was attained compared to bare Co–B. Among the all catalysts tested, Co–W–B/PPy with 7.5% W possessed the remarkable catalytic performance of 9.92 L min^?1 g^?1 and high stability over five cycles with the apparent activation energy of 49.18 kJ mol^?1.     

Nanocrystalline cobalt–nickel–boron (metal boride) catalysts for efficient hydrogen production from the hydrolysis of sodium borohydride

Innovative metal boride nanocatalysts containing crystalline Co–Ni based binary/ternary boride phases were synthesized and used in the hydrolysis of NaBH₄. All the as-prepared catalysts were in high-purity with average particle sizes ranging between ~51 and 94 nm and consisting of different crystalline phases (e.g. CoB, Co₂B, Co₅B₁₆, NiB, Ni₄B₃, Ni₂Co_0·67B_0.33). The synergetic effect of the different binary/ternary boride phases in the composite catalysts had a positive role on the catalytic performances thus, while the binary boride containing phases of unstable cobalt borides or single Ni₄B₃ were not showing any catalytic activity. The Co–Ni–B based catalyst containing crystalline phases of CoB–Ni₄B₃ exhibited the highest H₂ production rate (500.0 mL H₂ min^?1 g_cat^?1), with an apparent activation energy of 32.7 kJ/mol. The recyclability evaluations showed that the catalyst provides stability even after the 5th cycle. The results suggested that the composite structures demonstrate favorable catalytic properties compared to those of their single components and they can be used as alternative and stable catalysts for efficient hydrogen production from sodium borohydride.     

Self-optimized and renewable Ni–Co alloy@Co–Co2C catalyst for higher alcohols synthesis from syngas

Higher alcohols synthesis (HAS) from syngas (CO/H₂) has attracted widespread attention, while the low selectivity and poor stability of the catalysts mainly stumbled its industrial application. In the work, Ni–Co alloy nanoparticles (NPs) derived from Co_1-xNi_xAl₂O₄ loaded on the SiO₂ with large specific surface area were prepared; and during reaction, the highly dispersed Ni–Co alloys were self-optimized to Ni–Co alloy@Co–Co₂C. Importantly, Ni–Co alloy@Co–Co₂C can be regenerated through oxidation - reduction - self-optimization process. Characteristic results indicated that the structural liberalization during the reaction process inhibited the loss of Ni, regulated and balanced the dual active sites of the catalyst and the Ni–Co alloys were regenerated after the re-oxidation and re-reduction process. The optimized catalyst exhibited excellent catalytic performance, including a high total selectivity to alcohols of 39.3% and an excellent catalytic stability at 250 °C, 3.5 MPa (H₂/CO = 2) and a space velocity of 6000 mL (g_cat h)^?1. In addition, the Ni–Co alloy@Co–Co₂C catalyst after stability test could recover its original catalytic performance after re-oxidation and re-reduction. The renewable characteristics and superior catalytic performance of Ni–Co alloy@Co–Co₂C made the catalyst to be one of the potential industrial catalysts for HAS.     

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 production from sodium borohydride originated compounds: Fabrication of electrospun nano-crystalline Co3O4 catalyst and its activity

Electrospun nanofibers are prepared through electrospinning followed by post-treatment and preferred to use in catalytic applications. The electrospinning provides advantages for active catalysts design based on activity profiles and features of catalyst. In the present study, we fabricated nano-crystalline cobalt oxide (Co₃O₄) catalyst by electrospinning technique followed by thermal conditioning. Polyacrylonitrile (PAN) based Co as-spun mats (Co/NMs) with homogeneous diameter were prepared by electrospinnig process under several conditions as applied voltage (15–25 kV), working distance (5–7.5 cm) with the feed rate of 1 ml min⁻¹. The calcination process as a post-treatment was applied at different temperatures (232 °C, 289 °C and 450 °C) to obtain electrospun nano-crystalline Co₃O₄ catalyst. Co/NMs catalysts were characterized by XRD, SEM, TEM, XPS, FT-IR, TG/DTG, and ICP-MS techniques. The parametrically study was performed for evaluating the hydrogen production activity of catalyst from sodium borohydride (NaBH₄, SBH) and its originated compounds as ammonia borane (NH₃BH₃, AB) and methyl-amine borane (CH₃NH₂BH₃, MeAB). The relation between the internal-external properties and catalytic activities of catalysts for hydrogen production was investigated. The beadless Co/NMs-1 catalyst with homogeneous diameter was obtained under electrospinnig process conditions at 15 kV applied voltage and 7.5 cm working distance. All catalysts showed activity for hydrogen production, also the significant effect of post treatment process was observed on the catalytic activity as given order: Co/NMs-1₄₅₀ > Co/NMs-1₂₈₉ > Co/NMs-1 > Co/NMs-1₂₃₂. Furthermore, mesoporous Co₃O₄ cubic crystals (26 nm) in fibrous architecture was prepared by 450 °C-post-treatment. Hydrogen production rates were recorded at 60 °C as 2.08, 2.20, and 6.39 l H₂.g_cat⁻¹min⁻¹ for NaBH₄, CH₃NH₂BH₃, and NH₃BH₃, respectively.     

Boosting hydrogen production by ethanol steam reforming on cobalt-modified Ni–Al2O3 catalyst

Ethanol steam reforming (ESR) is one of the most promising reliable and recyclable technologies for hydrogen production. However, the development of robust, efficient Ni-based catalysts that minimize metal sintering and carbon deposition remains a key challenge. The influence of cobalt loading and ESR conditions on H₂ selectivity and catalytic stability is the focus of this study. Ni–Co/Al₂O₃ catalysts with various Co percentages were prepared by the co-impregnation method and complementary characterization tests were performed. Among the catalysts tested, Ni–Co/Al₂O₃ (5 wt% Co) exhibited the smallest metal crystallite size, the highest surface area, and the best catalytic performance. Thereafter, the effects of temperature, LHSV and S:C molar ratio were studied. 100% ethanol conversion and maximum H₂ selectivity (95.14%) were reached at 600 °C, 0.05 L/g_cat.h and S:C molar ratio of 12:1. Furthermore, ethanol turnover frequency (TOF) was computed for each catalyst. TOF results showed that the Ni–Co interaction had an impact on the catalytic activity. Finally, Ni2CoAl was subjected to 50-h stability test and only 6.12 mg_carbon/g_cat.h coke deposition was observed.     

Stability and kinetic studies of MOF‐derived carbon‐confined ultrafine Co catalyst for sodium borohydride hydrolysis

A mesoporous carbon‐confined cobalt (Co@C) catalyst was fabricated by pyrolysis of macroscale Co‐metal–organic framework (MOF) crystals and used to catalyze NaBH₄ hydrolysis for hydrogen production. To reveal the structural changes of cobalt nanoparticles, we characterized the fresh and used Co@C catalysts using X‐ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and N₂ adsorption. This MOF‐derived Co@C exhibits high and stable activity toward NaBH₄ hydrolysis. No obvious agglomeration of Co nanoparticles occurred after five consecutive runs, implying good resistance of Co@C composite to metal aggregation. The kinetics of NaBH₄ hydrolysis was experimentally studied by changing initial NaBH₄ concentration, NaOH concentration, and catalyst dosage, respectively. It was found that the hydrogen generation rate follows a power law: r = A exp (?45.0/RT)[NaBH₄]^0.985[cat]^1.169[NaOH]^?0.451 .