Ru-Ni/TiO2 was synthesized for photo(catalytic) NaBH4 hydrolysis to generate H2. The specific hydrogen generation rate (HGR) reached a maximum of 220 mL center dot min-1 center dot g-1 at the optimal NaBH4 concentration of 1.058 mol center dot kg-1 and increased sharply with temperature, with activation energy (Ea) of 57.57 kJ center dot mol-1. The catalyst performed best in alkaline-free solutions and retained 83% and 63% of its initial activity after two and six reuse cycles, respectively. UV-irradiated catalyst displayed significant performance, achieving HGR values up to 1130 mL center dot min-1 center dot g-1, more than an order of magnitude higher than the dark catalytic rate at the same temperature. These results demonstrate that the Ru-Ni/TiO2 system functions as an effective bifunctional catalyst,-facilitating light-assisted enhancement for on-demand H2 production.

In this study, the use of ruthenium (Ru) and platinum (Pt)-decorated zinc oxide-titanium oxide (ZnO/TiO2) nanostructured catalysts for catalytic and photoelectrochemical (PEC) sodium borohydride (NaBH4) hydrolysis for hydrogen production was investigated. Catalytic studies of ZnO/TiO2/Ru-Pt electrodes conducted under dark conditions have shown that the hydrolysis process does not depend on the structure of the catalyst. In contrast to the dark catalytic measurements, it was found that the morphology of the nanocatalyst and the metal used to sensitize the nanocatalyst affected the PEC performance. From the BET analysis, ZnO nano-flower (NF) structures have a surface area of 80 m2g−1, while the surface area of nanosheet (NS) structures is calculated as 17 m2g−1. In parallel with their high surface area, ZnO NF structures were found to have higher optical absorption in the UV and visible region than NS structures. However, the high photosensitivity of NS structures compared to the NF enabled them to exhibit very good PEC performance, especially at high NaBH4 concentrations. In this study, the highest applied bias photoconversion efficiency was observed in ZnO NS/TiO2/Ru catalysts with 9.0

The influence of temperature, as well as NaOH and NaBH4 concentrations on the rate of catalytic hydrolysis is investigated. Finely dispersed powders of platinum and ruthenium on a titanium oxide carrier were used as model catalysts. The activation energies in an aqueous and aqueous-alkaline solutions of NaBH4, equal to 60.5 and 53.2 kJ/mole for Pt/TiO2 and 62 and 64.65 kJ/mole for Ru/TiO2, respectively, were determined. It was found that with an increase in the concentration of NaOH, the rate of hydrogen generation with Ru/TiO2 decreases, and with Pt/TiO2 passes through a maximum in the range 0.5–2 M NaOH. It is shown that with traditional processing of kinetic data for determining the activation energy, its dependence on the sorption properties of the surface and the concentration of the solution is revealed.

Highly stable platinum (Pt) and ruthenium (Ru)-based catalysts on titanium oxide (TiO2) nanoparticle support were prepared. The productivity of hydrogen generation from sodium borohydride (NaBH4) hydrolysis was observed to be as high as 95%. The activation energies for the hydrolysis reaction in the presence of Ru/TiO2 in aqueous and alkaline solutions were 62.00 and 64.65 kJ mol-1, respectively. On the other hand, the activation energy value of the hydrolysis reaction with the Pt/TiO2 catalyst decreased from 60.5 to 53.2 kJ mol-1, and the solution was changed from an aqueous to an alkaline medium. The experimental results have indicated that NaOH concentration (ranging from 0.5 to 2 M) affected the hydrogen generation rate (HGR) differently for both metals on the TiO2 support. Consequently, the HGR of the hydrolysis reaction in the presence of the Ru/TiO2 catalyst decreased with increasing NaOH concentration, whereas the Pt/TiO2 catalyst efficiency increased with increasing NaOH concentration.

The article presents the results of experiments of the hydrolysis process with a Co/TiO 2 catalyst and homogeneous experiments in an aqueous solution of sodium borohydride (NaBH 4 ) aimed to the test the developed model of heterogeneous processes. In data processing of catalytic experiments, we use the method of their correction to exclude the rate of homogeneous hydrolysis. We consider the adsorption/desorption model, in which two types of particles can be adsorbed, i.e. water molecules and BH 4 − ·H + complexes. As a result of the analysis of possible irreversible heterogeneous reactions and the experimental dependences of the hydrogen generation rates, it is concluded that the main hydrolysis reaction on the Co/TiO 2 catalyst occurs upon collisions of BH 4 − ion from the solution with adsorbed water molecules. We observed the growth of the specific rate of hydrogen generation with an increase in the degree of NaBH 4 decomposition in all experiments with this catalyst. Two hypotheses have been suggested to explain this effect.

A study has been made of the influence of temperature, NaON, and concentrations of NaBH4 on the rate of catalytic hydrolysis under isothermal and adiabatic conditions. Finely divided Co/TiO2 powder was used as the model catalyst. The catalyst preserves its initial activity during 20 cycles, ensuring an NaBH4 conversion of 94–98

The influence of the structural differences in TiO2 (Degussa P25 and Mesh 325) as supporting materials for Co nanoparticles has been revealed in aqueous and alkaline NaBH4 hydrolysis. The activation energies for TiO2 (Mesh 325)/Co and Co/TiO2 (P25)/Co catalysts in aqueous solution of NaBH4 were 64.3 kJ . mol-1 and 56.76 kJ . mol-1, respectively. On the other hand, the activation energy values of the hydrolysis process in alkaline NaBH4 solutions using TiO2 (Mesh 325)/Co and TiO2 (P25)/Co catalysts have been calculated as 55 kJ . mol-1 and 45.2 kJ . mol-1, respectively. Consequently, hydrogen generation rate (HGR) for TiO2(Mesh 325)/Co and TiO2(P25)/Co in an aqueous-alkaline solution are 145 and 363 ml . min . gcat-1, respectively which are twice higher in that of aqueous NaBH4 hydrolysis reaction.

Kinetic experiments were carried out on the hydrolysis of concentrated aqueous and aqueous alkaline solutions of NaBH4 with a Co/TiO2 catalyst. The experiments in the aqueous NaBH4 solutions were performed at molal concentrations of 0.25, 1, and 4 mol/kg. In the aqueous alkaline solutions with molal NaBH4 concentrations of 0.25 and 1 mol/kg, the molal NaOH concentrations were varied in the range 0.05–8 mol/kg. The activation energies in the aqueous solution and the aqueous alkaline solutions were found to be 64.3 and 53.6 kJ/mol, respectively. Features of the kinetic curves and the possible kinetic schemes were discussed.

In this study, catalytic hydrolysis of aqueous solutions of NaBH4 under isothermal and adiabatic conditions was investigated. A finely dispersed cobalt powder based on titanium oxide was used as a model catalyst. It was determined that catalytic activity of this catalyst practically did not change after 20 cycles. It was shown that the activation energy, determined by the rate of hydrogen generation, depends on NaBH4 concentrations. We believe that this effect is associated with sorption/desorption processes. If to conduct hydrolysis under conditions close to adiabatic, the time of hydrolysis is significantly reduced. As united solution of equations of kinetics and energy conversation shows, the data of experiments in a thermally insulated reactor can be reasonably predicted.

The influence of the structural differences in titanium dioxide (TiO2- Degussa P25 and Mesh 325) as supporting materials for cobalt (Co) nanoparticles, has been revealed in aqueous and alkaline sodium borohydride (NaBH4) hydrolysis. The very little amount of Co nanoparticles, which was 2.2 and 1.5 wt

In this study, g-C3N4-TiO2 nanocomposite structure has been loaded with Co3O4 via electroless plating and thermal annealing to form Co3O4@g-C3N4-TiO2 catalyst material for H2 generation from NaBH4 hydrolysis. The material characterizations of the fabricated catalyst have been performed before and after exposure to an aqueous NaBH4 solution to understand the changes in catalytic performance and material properties. The Arrhenius activation energies have been determined to be 58 kJ mol−1. The hydrogen generation rates have been observed as 180 and 1200 mL min−1 gcat−1 for the catalyst hydrolysis of NaBH4 at 30 °C and 60 °C, respectively. The catalytic activity performed in NaBH4 solution exhibited good reusability.

The results of experimental studies on the hydrolysis of concentrated aqueous solutions of sodium borohydride in a concentration range of 1.05–6.3 mol/kg at temperatures of 20–80°C with the use of Co/TiO2 powder as a model catalyst are presented. Based on the results of the experiments, an approximation of the rate of the process was proposed for the kinetic regime of hydrolysis taking into account the non-single-channel nature of hydrolysis due to the introduction of a linear dependence of the activation energy on the degree of hydrolysis.

In this study, g-C 3 N 4 -TiO 2 nanocomposite structure has been loaded with Co 3 O 4 via electroless plating and thermal annealing to form Co 3 O 4 @g-C 3 N 4 -TiO 2 catalyst material for H 2 generation from NaBH 4 hydrolysis. The material characterizations of the fabricated catalyst have been performed before and after exposure to an aqueous NaBH 4 solution to understand the changes in catalytic performance and material properties. The Arrhenius activation energies have been determined to be 58 kJ mol −1 . The hydrogen generation rates have been observed as 180 and 1200 mL min −1 g cat −1 for the catalyst hydrolysis of NaBH 4 at 30 °C and 60 °C, respectively. The catalytic activity performed in NaBH 4 solution exhibited good reusability. Graphical Abstract

A phenomenological model is developed to take into account the effect of hydration complexes on the properties of electrolytes. The results of validation of the model are demonstrated for experimental pH values of aqueous solutions of sodium metaborate within a molal concentration range of 10−3–4.0 mol kg−1 at the temperatures 20, 25, and 50 °C.

The authors have presented a mathematical model of heat- and mass-transfer processes in a circulating-type reactor implementing the hydrolysis of sodium borohydride in the hydrogen generator. The model was used to analyze two methods of control of the generator output and can be applied to scaling and optimization of structures of generators of this type.

In this study, nickel catalyst in the form of meshes was used in the stationary hydrogen generator with the circulation circuit of reactor to produce hydrogen from sodium borohydride. Based on the tests carried out, optimum parameters of the working process (working solution composition, temperature, pressure) have been determined on sodium borohydride with a capacity on hydrogen of up to 2 nm3/h.

A novel circulation type a hydrogen generator operating on sodium borohydride sodium borate solution has been developed. The major parameters, such as operation temperature, concentration of the sodium borohydride and metaborate, catalytic activity, start up conditions, and removal of NaBO2 as a product of the sodium borohydride hydrolysis have been analyzed. Generation of hydrogen was evaluated for aqueous NaBH4 solutions in the range of 15-23 wt. % NaBH4 in presence of the alumina supported Pt, Pd, Rh and Ni catalysts. The main trends in hydrogen gas generation with respect to the solution temperature and pressure in the reactor were analyzed. The catalytic efficiency and the rate of the hydrogen gas generation (1.5 Nm(3)/h) at the average hydrogen yield of 97-98.5% is sufficient for operation of the PEMFC Nexa(TM) Power module from Ballard. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Stability of sodium borohydride in the form of concentrated solutions and suspensions and solids corresponding to a crystal hydrate in composition was studied. The effects of temperature, concentrations of sodium borohydride and alkali, and nature of alkali metal cation on the rate of sodium borohydride hydrolysis were studied.