Search Results (54)

The growing environmental and economic impacts of carbon-based fuels have accelerated the search for sustainable alternatives, with hydrogen (H₂) emerging as a clean and efficient energy carrier. Sodium borohydride (NaBH₄) is a promising hydrogen storage compound, due to its high hydrogen content (10.6 wt%) and stability under ambient conditions. However, its hydrolysis with water proceeds slowly without an effective catalyst. In this study, gold nanoparticle-decorated spherical carbon (AuSC) composites were synthesized and evaluated as catalysts for NaBH₄ hydrolysis. The spherical carbon support, prepared via a glucose-mediated route, provided a high-surface-area and conductive matrix that dispersed and stabilized Au nanoparticles, preventing agglomeration. Catalyst morphology and composition were characterized using XRD, TEM, SEM, and EDS analyses. The AuSC catalyst exhibited excellent catalytic activity, producing 21.8 mL of H₂ at pH 7, 303 K, and 835 μmol NaBH₄. The activation energy (E_a) was determined to be 51.6 kJ mol⁻¹, consistent with a heterolytic B–H bond cleavage mechanism at the Au–C interface. The TON (2.82 × 10⁴) and TOF (1.41 × 10⁴ h⁻¹) values confirmed high intrinsic catalytic efficiency. These results demonstrate that Au-decorated spherical carbon composites are efficient, stable, and promising catalysts for hydrogen generation from NaBH₄ hydrolysis under mild conditions. Full article

In this study, we report the preparation of platinum nanoparticles (Pt NPs) deposited on HTiNbO₅ and the application of the resultant material in the catalytic decomposition of sodium borohydride (NaBH₄) to generate hydrogen. The starting material, KTiNbO₅, was prepared through a solid-state process involving Nb₂O₅, K₂CO₃, and TiO₂. The subsequent treatment with HNO₃ resulted in the exchange of potassium by protons, rendering HTiNbO₅. This material served as support for Pt nanoparticles (3.6 ± 0.7 nm), producing Pt NPs/HTiNbO₅. All compounds were characterized using TGA, FTIR, XRD, Raman, SEM-EDS, and HRTEM. The influence of different factors on the reaction kinetics was evaluated, resulting in a hydrogen generation rate (HGR) of 22,790.18 $\mathrm{m}\mathrm{L} {\mathrm{m}\mathrm{i}\mathrm{n}}^{-1}{\mathrm{g}}_{\mathrm{c}\mathrm{a}\mathrm{t}}^{-1}$ at 50 °C. The activation energy (41.83 kJ mol⁻¹) was also determined. A mechanistic study with deuterated water revealed a kinetic isotopic effect (KIE) value of 1.27, indicating the dissociation of B-H from BH₄⁻ as the rate-determining step of the process. Furthermore, the reuse and durability of the material were evaluated, revealing a catalyst performance close to 100% over the 10 tested cycles. Therefore, it can be concluded that the synthesized material, Pt-nanoparticles dispersed on HTiNbO₅, exhibits excellent performance and is suitable for hydrogen evolution from NaBH₄. Full article

Because of fossil fuel depletion and its inevitable danger to the environment, researchers have worked on alternative fuel sources like hydrogen (H₂), which can be obtained via renewable energy sources like biomass, solar, geothermal, ocean, wind, hydropower, and nuclear. H₂ has many advantages. It has a high heating value compared to traditional fossil fuels. It can be synthesized from water or biomass without releasing any greenhouse gases (GHGs). Nowadays, the most popular hydrogen production methods are sodium borohydride (NaBH₄) hydrolysis, photocatalysis, and water electrolysis. Among them, the NaBH₄ hydrolysis reaction is preferred due to its advantages. It is possible to reach high hydrogen generation rates under mild conditions with this reaction. In this work, thermodynamic analysis was carried out with Gaussian 09W software. At first, the products and reactants of the reaction were drawn. Then, enthalpy and free energy information were taken for the reaction. Calculations were carried out via the Hartree–Fock Method for each molecule. Basis set was selected as 6-31G(d). Reaction conditions were assumed as 298 K and 1 atm. As a result of the computations, the enthalpy and free energy of the reaction were found as −58.0315 kcal/mol and −72.6141 kcal/mol, respectively. This means that this reaction was exothermic because of the negative sign of enthalpy, and the negative sign of Gibbs energy is related to spontaneous reaction. Full article

The reliance on carbon-based fuels remains a major contributor to greenhouse gas emissions, emphasizing the need for sustainable alternatives such as hydrogen. Sodium borohydride (NaBH₄), with a hydrogen content of 10.6 wt%, is a promising chemical hydrogen storage material capable of releasing four moles of H₂ per mole through hydrolysis; however, effective catalysts are essential for practical implementation. In this study, silver nanoparticles supported on glucose-derived carbon microspheres (AgSC) were synthesized and evaluated for catalytic NaBH₄ hydrolysis. Structural characterization (XRD, TEM, SEM, EDS) confirmed the uniform dispersion of metallic silver nanoparticles on the carbon support with no detectable Ag₂O phase. AgSC exhibited superior catalytic activity compared to unsupported Ag or bare carbon, achieving the highest hydrogen generation under neutral pH, elevated temperatures, and 835 µmol NaBH₄. The catalyst displayed an activation energy of 54 kJ mol⁻¹, turnover numbers (TONs) of 1.4 × 10⁵–1.9 × 10⁵, and turnover frequencies (TOFs) of 7.1 × 10⁴–9.3 × 10⁴ h⁻¹, demonstrating efficient utilization of active sites. pH-dependent studies revealed optimal hydrogen yield under neutral conditions, while acidic and basic media reduced performance due to surface poisoning and BH₄⁻ stabilization, respectively. Reusability tests showed only ~5% activity loss after five cycles. These findings establish AgSC as a stable, efficient, and recyclable catalyst for on-demand hydrogen generation, supporting sustainable clean fuel technologies. Full article

In our previous work, we fabricated Ni single-atoms within Beta zeolite (Ni₁@Beta-NO₃⁻) using NiNO₃·6H₂O as a metal precursor without any chelating agents, which exhibited exceptional performance in the selective hydrogenation of furfural. Owing to the confinement effect, the as-encapsulated nickel species appears in the form of Ni⁰ and Ni^δ+, which implies its feasibility in metal catalysis and coordination catalysis. In the study reported herein, we further explored the hydrogen production and olefin oligomerization performance of Ni₁@Beta-NO₃⁻. It was found that Ni₁@Beta-NO₃⁻ demonstrated a high H₂ generation turnover frequency (TOF) and low activation energy (E_a) in a sodium borohydride (NaBH₄) hydrolysis reaction, with values of 331 min⁻¹ and 30.1 kJ/mol, respectively. In ethylene dimerization, it exhibited a high butylene selectivity of 99.4% and a TOF as high as 5804 h⁻¹. In propylene oligomerization, Ni₁@Beta-NO₃⁻ demonstrated high selectivity (75.21%) of long-chain olefins (≥C₆⁺), overcoming the problem of cracking reactions that occur during oligomerization using H-Beta. Additionally, as a comparison, the influence of the metal precursor (NiCl₂) on the performance of the encapsulated Ni catalyst was also examined. This research expands the application scenarios of non-noble metal single-atom catalysts and provides significant assistance and potential for the production of H₂ from hydrogen storage materials and the production of valuable chemicals. Full article

Transition metal oxide aerogels (AGLs) have attracted considerable attention in recent years due to their exceptional properties, including high surface area, significant porosity, and ultralow density. In this study, we report the first-time synthesis of zinc oxide nano-wafers and zinc aerogels for application as supercapacitor electrodes. The aerogels were synthesized via a novel one-pot hydrolysis method using NaBH₄ as a reducing agent and subsequently annealed at 200 °C (Zn_AGL(200)) and 450 °C (Zn_AGL(450)) to investigate the influence of temperature on their electrochemical properties. Structural and morphological characterizations were conducted using XRD, FTIR, BET, XPS, SEM, and TEM analyses. Among the fabricated electrodes, the aerogel annealed at 200 °C (Zn_AGL(200)) exhibited superior energy storage performance, attributed to its amorphous, continuous network structure, which enhanced its surface area and reduced its density compared to both the as-synthesized (Zn_AGL(RT)) and 450 °C-annealed (Zn_AGL(450)) counterparts. A two-electrode device demonstrated excellent cycling stability over 10,000 cycles, achieving an energy density of 7.97 Wh/kg and a power density of 15 kW/kg. These findings highlight the potential of zinc aerogels as materials for next-generation lightweight energy storage systems, with promising applications in industrial, mechanical, and aerospace technologies. Full article

Aqueous gel-casting provides a cost-effective and scalable approach for synthesizing nano-spherical Co₃O₄ powders, enabling precise control over particle morphology. In this study, Co₃O₄ powders were prepared using this method and evaluated as a catalyst precursor for the hydrolysis of sodium borohydride (NaBH₄). The effects of the monomer (acrylamide, AM)-to-metal molar ratio and initiator content (ammonium persulphate, APS) on particle size and catalytic performance were systematically explored. X-ray diffraction (XRD) analysis confirmed the formation of the Co₃O₄ phase at 400 °C, while transmission electron microscopy (TEM) images revealed particle sizes ranging from 16 to 85 nm, with higher AM and APS concentrations promoting finer particles. The optimized catalyst achieved a high hydrogen generation rate (HGR) of 28.13 L min⁻¹·cat.⁻¹, demonstrating excellent catalytic activity. Moreover, in situ-formed cobalt boride, derived from Co₃O₄ calcined at 600 °C for 2 h, exhibited an activation energy of 51.81 kJ mol⁻¹, comparable to Ru-based catalysts. This study underscores the aqueous gel-casting technique as a promising strategy for synthesizing efficient and low-cost hydrogen generation catalysts, offering an alternative to noble metal-based materials. Full article

Reducing dehydrogenation temperature while preserving high hydrogen generation capacity obstructs the hydrolysis of sodium borohydrides (NaBH₄). The two-dimensional (2D) MAX phase of titanium aluminum carbide (Ti₃AlC₂) and MXene (Ti₃C₂T_x) multilayers was investigated for hydrogen generation via NaBH₄ hydrolysis with and without light. The material was characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS). The activity of Ti₃AlC₂ was significantly enhanced by the integration of UV light radiation during hydrolysis. Ti₃AlC₂/Ti₃C₂T_x improved the dehydrogenation rates of NaBH₄ at ambient conditions and maintained high hydrogen generation rates (HGRs) over time compared to a conventional method. It exhibited a HGR of 200–300 mL·min⁻¹·g⁻¹. Photo-assisted hydrolysis over the catalyst can be maintained for several times at ambient temperature. The catalyst demonstrated effective performance even after five cycles of usage. Full article

Porous carbon particles (PCPs) prepared from sucrose via the hydrothermal method and its modified forms with polyethyleneimine (PEI) as PCP-PEI were used as templates as in situ metal nanoparticles as M@PCP and M@PCP-PEI (M:Co, Ni, or Cu), respectively. The prepared M@PCP and M@PCP-PEI composites were used as catalysts in the hydrolysis of NaBH₄ and NH₃BH₃ to produce hydrogen (H₂). The amount of Co nanoparticles within the Co@PCP-PEI structure was steadily increased via multiple loading/reducing cycles, e.g., from 29.8 ± 1.1 mg/g at the first loading/reducing cycles to 44.3 ± 4.9 mg/g after the third loading/reducing cycles. The Co@PCP-PEI catalyzed the hydrolysis of NaBH₄ within 120 min with 251 ± 1 mL H₂ production and a 100% conversion ratio with a 3.8 ± 0.3 mol H₂/(mmol cat·min) turn-over frequency (TOF) and a lower activation energy (Ea), 29.3 kJ/mol. In addition, the Co@PCP-PEI-catalyzed hydrolysis of NH₃BH₃ was completed in 28 min with 181 ± 1 mL H₂ production at 100% conversion with a 4.8 ± 0.3 mol H₂/(mmol cat·min) TOF value and an Ea value of 32.5 kJ/mol. Moreover, Co@PCP-PEI composite catalysts were afforded 100% activity up to 7 and 5 consecutive uses in NaBH₄ and NH₃B₃ hydrolysis reactions, respectively, with all displaying 100% conversions for both hydrolysis reactions in the 10 successive uses of the catalyst. Full article

In this study, bimetallic NiCo nanoparticles (NPs) were encapsulated within the mesopores of carboxylic acid functionalized mesoporous silica (CMS) through the chemical reduction approach. Both NaBH₄ and NH₃BH₃ were used as reducing agents to reduce the metal ions simultaneously. The resulting composite was used as a catalyst for hydrolysis of ammonia borane (NH₃BH₃, AB) to produce H₂. The bimetallic NiCo NPs supported on carboxylic group functionalized mesoporous silica, referred to as Ni_xCo_100−x@CMS, exhibited significantly higher catalytic activity for AB hydrolysis compared to their monometallic counterparts. The remarkable activity of Ni_xCo_100−x@CMS could be ascribed to the synergistic contributions of Ni and Co, redox reaction during the hydrolysis, and the fine-tuned electronic structure. The catalytic performance of the Ni_xCo_100−x@CMS nanocatalyst was observed to be dependent on the composition of Ni and Co. Among all the compositions investigated, Ni₄₀Co₆₀@CMS demonstrated the highest catalytic activity, with a turn over frequency (TOF) of 18.95 mol_H2min⁻¹mol_catalyst⁻¹ and H₂ production rate of 8.0 L min⁻¹g⁻¹. The activity of Ni₄₀Co₆₀@CMS was approximately three times greater than that of Ni@CMS and about two times that of Co@CMS. The superior activity of Ni₄₀Co₆₀@CMS was attributed to its finely-tuned electronic structure, resulting from the electron transfer of Ni to Co. Furthermore, the nanocatalyst exhibited excellent durability, as the carboxylate group in the support provided a strong metal–support interaction, securely anchoring the NPs within the mesopores, preventing both agglomeration and leakage. Full article

The performance of nickel and platinum bimetallic nanoparticles (NPs) supported on potassium niobate (KNbO₃) is evaluated in the catalytic hydrolysis of sodium borohydride (NaBH₄) to generate hydrogen (H₂). KNbO₃ was synthesized via a hydrothermal route using Nb₂O₅ and KOH as precursors. X-ray diffraction (XRD) confirmed the crystalline orthorhombic structure of KNbO₃. The Ni/Pt NPs, with an average size of 4.66 nm and a spherical morphology, were uniformly dispersed on the surface of KNbO₃ nanosheets. The N₂ physisorption isotherms of KNbO₃ and Ni/Pt NPs were classified as type V with H3 hysteresis, showing specific surface areas of 0.170 and 2.87 m² g⁻¹, respectively. Catalytic performance studies examined various Ni/Pt molar ratios, with the 1:3 ratio (mol/mol) demonstrating the highest efficiency. Kinetic analysis of NaBH₄ hydrolysis showed that the data fit the pseudo-first-order model. An increase in temperature enhanced the hydrogen generation rate (HGR), reaching 2068.3 mL g_cat⁻¹ min⁻¹ at 315.05 K. The apparent activation energy (E_a) was determined to be 29.9 kJ mol⁻¹. Durability assays showed only an 11% decrease in activity after 11 catalytic cycles. Thus, a promising, easy-to-synthesize, and environmentally friendly catalyst for NaBH₄ hydrolysis has been developed. Full article

In this study, hydrogen production through the hydrolysis, ethanolysis, and methanolysis reactions of NaBH₄ using adipic acid as a catalyst was investigated for the first time. Adipic acid solutions were prepared with methanol and ethanol at concentrations of 0.1, 0.2, 0.3, 0.4, and 0.5 M. In these reactions, NaBH₄-MR (methanolysis) and NaBH₄-ER (ethanolysis) reactions were carried out at 30, 40, and 50 °C with NaBH₄ concentrations of 1.25%, 2.5%, and 5%. Hydrolysis reactions (NaBH₄-HR) were conducted at 0.1 M under the same conditions. In the ethanolysis and methanolysis reactions at 30 °C, total hydrogen conversion was achieved at 0.3 M, 0.4 M, and 0.5 M. However, in the hydrolysis reactions, total hydrogen production was only obtained at 50 °C. It was observed that in the NaBH₄-MR and NaBH₄-ER reactions, total hydrogen conversion could be achieved within 4–5 s. The utilization of adipic acid as a catalyst for hydrogen production from NaBH₄ through ethanolysis and methanolysis reactions is proposed as a highly efficient and fast method, characterized by impressive conversion rates. Full article

This study investigates the significant impact of metal–support interactions on catalytic reaction mechanisms at the interface of oxide-supported metal nanoparticles. The distinct and contrasting effects of SiO₂ and TiO₂ supports on reaction dynamics using NaBD₄ were studied and focused on the relative yields of [HD]/[H₂] and [D₂]/[H₂]. The findings show a consistent increase in HD yields with rising [BD₄⁻] concentrations. Notably, the sequence of HD yield enhancement follows the order of TiO₂-Au⁰-NPs < Au⁰-NPs < SiO₂-Au⁰-NPs. Conversely, the rate of H₂ evolution during BH₄^- hydrolysis exhibits an inverse trend, with TiO₂-Au⁰-NPs outperforming the others, followed by Au⁰-NPs and SiO₂-Au⁰-NPs, demonstrating the opposing effects exerted by the TiO₂ and SiO₂ supports on the catalytic processes. Further, the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) confirms the catalytic mechanism, with TiO₂-Au⁰-NPs demonstrating superior activity. The catalytic activity observed aligns with the order of TiO₂-Au⁰-NPs > Au⁰-NPs > SiO₂-Au⁰-NPs, suggesting that SiO₂ donates electrons to Au⁰-NPs, while TiO₂ withdraws them. It is of interest to note that two very different processes, that clearly proceed via different mechanisms, are affected similarly by the supports. This study reveals that the choice of support material influences catalytic activity, impacting overall yield and efficiency. These findings underscore the importance of selecting appropriate support materials for tailored catalytic outcomes. Full article

A disordered sodium borohydride (NaBH₄) environment to facilitate Na⁺ mobility was achieved by partially hydrolyzing NaBH₄ and this significantly improved Na⁺ ionic conductivity to 10⁻³ S cm⁻¹ at 75 °C. The reaction rate of NaBH₄ self-hydrolysis, however, is determined by several parameters, including the reaction temperature, the molar ratio between NaBH₄ and H₂O, and the pH value; but these factors are hard to control. In this paper, poly(ethylene oxide) (PEO), capable of retaining H₂O through hydrogen bonding, was used in an attempt to better control the amount of H₂O available for NaBH₄ self-hydrolysis. This strategy led to the ionic conductivity of 1.6 × 10⁻³ S cm⁻¹ at 45 °C with a Na⁺ transference number of 0.54. The amorphous nature of the PEO matrix in hydrolyzed NaBH₄ is also believed to provide a conduction path for fast Na⁺ conduction. Full article

The production of high-purity hydrogen from hydrogen storage materials with further direct use of generated hydrogen in fuel cells is still a relevant research field. For this purpose, nickel-molybdenum-plated copper catalysts (NiMo/Cu), comprising between 1 and 20 wt.% molybdenum, as catalytic materials for hydrogen generation, were prepared using a low-cost, straightforward electroless metal deposition method by using citrate plating baths containing Ni²⁺–Mo⁶⁺ ions as a metal source and morpholine borane as a reducing agent. The catalytic activity of the prepared NiMo/Cu catalysts toward alkaline sodium borohydride (NaBH₄) hydrolysis increased with the increase in the content of molybdenum present in the catalysts. The hydrogen generation rate of 6.48 L min⁻¹ g_cat⁻¹ was achieved by employing NiMo/Cu comprising 20 wt.% at a temperature of 343 K and a calculated activation energy of 60.49 kJ mol⁻¹ with remarkable stability, retaining 94% of its initial catalytic activity for NaBH₄ hydrolysis following the completion of the fifth cycle. The synergetic effect between nickel and molybdenum, in addition to the formation of solid-state solutions between metals, promoted the hydrogen generation reaction. Full article