Hydrolysis Of BH Research Articles

ВЛИЯНИЕ ПРИМЕСЕЙ ПЕРЕХОДНЫХ МЕТАЛЛОВ Fe, Ni И Co НА КИНЕТИКУ ГИДРОЛИЗА BH− 4 -ИОНОВ В ЩЕЛОЧНЫХ РАСТВОРАХ

The influence of small amounts of the Fe, Co, and Ni impurities on the spontaneous hydrolytic process of borohydride was studied within a temperature range of 60–100°C. The object under study was a simulated solution containing 9.53 M of OH− ions and 0.14 M of BH− 4 ions, used as a fuel for borohydride fuel cells. The rate constant k of borohydride hydrolysis for a small amount of impurities at different temperature was estimated. The lowest non-accelerating concentrations of the impurities were established (∼10 ppm for iron; ∼1 ppm for cobalt). The strongest accelerating effect on the hydrolysis of BH− 4 ions was rendered by nickel impurities: self-hydrolysis was accelerated by 1.2 times for 1 ppm Ni. The ambiguous trend of the kinetic curves does not allow to accurately estimate the activation energy; however, the increased temperature enhances the catalytic effect of hydrolysis acceleration according to Arrhenius’ equation.

Thermal Dehydrogenation and Hydrolysis of BH3NH3 Catalyzed by Cyclic (Alkyl)(amino)carbene Iridium Complexes under Mild Conditions

Thermal Dehydrogenation and Hydrolysis of BH₃NH₃ Catalyzed by Cyclic (Alkyl)(amino)carbene Iridium Complexes under Mild Conditions

Single Pt atoms supported on oxidized graphene as a promising catalyst for hydrolysis of ammonia borane

Based on density functional theory calculations, the full hydrolysis of per NH3BH3 molecule to produce three hydrogen molecules on single Pt atoms supported on oxidized graphene (Pt1/Gr-O) is investigated. It is suggested that the first hydrogen molecule is produced by the combination of two hydrogen atoms from two successive B−H bonds breaking. Then one H2O molecule attacks the left *BHNH3 group (* represents adsorbed state) to form *BH(H2O)NH3 and the elongated O−H bond is easily broken to produce *BH(OH)NH3. The second H2O molecule attacks *BH(OH)NH3 to form *BH(OH)(H2O)NH3 and the breaking of O−H bond pointing to the plane of Pt1/Gr-O results in the desorption of BH(OH)2NH3. The second hydrogen molecule is produced from two hydrogen atoms coming from two H2O molecules and Pt1/Gr-O is recovered after the releasing of hydrogen molecule. The third hydrogen molecule is generated by the further hydrolysis of BH(OH)2NH3 in water solution. The rate-limiting step of the whole process is the combination of one H2O molecule and *BHNH3 with an energy barrier of 16.1 kcal/mol. Thus, Pt1/Gr-O is suggested to be a promising catalyst for hydrolysis of NH3BH3 at room temperature.

The high utilization of fuel in direct borohydride fuel cells with a PdNi x -B/carbon nanotubes-catalysed anode

Abstract Direct borohydride fuel cells (DBFCs) exhibit the potential for a wide range of applications due to their high energy and power density; however, the hydrolysis of BH4− significantly limits the use of DBFCs. In this paper, PdNix-B/carbon nanotubes (PdNix-B/CNTs) (x = 0, 0.3, 0.6, 0.9) composites have been prepared by a chemical reduction method in which PdNix-B nanoparticles of approximately 3.5 nm are grown on the surface of carbon nanotubes. A cell was assembled with PdNix-B/CNTs as the anode catalyst, a polymer fibre membrane (PFM) as a substitute for the Nafion membrane and LaNiO3 as the cathode catalyst. The results show that the Ni element displays an ability to balance the competition between the hydrolysis and oxidation of BH4−. A peak power density of 105 mW cm−2 (x = 0.9) was achieved at 25 °C. However, the highest fuel efficiency of 69% was achieved at x = 0.3, and the corresponding power density was 87 mW cm−2, which represents the best comprehensive performance of these DBFCs.

Comparison of the electrochemical oxidation of borohydride and dimethylamine borane on platinum electrodes: Implication for direct fuel cells

The electrochemical behaviour of dimethylamine borane and borohydride on platinum electrodes was investigated by cyclic voltammetry and polarization curves in discharges processes. Several overlapping peaks appear in the domain of hydrogen oxidation, i.e., in the potential range of −1.25 V to −0.50 V versus Ag/AgCl, mainly with the borohydride. This behaviour is associated with the hydrolysis of BH 4 − or (CH 3) 2NHBH 3. As a consequence of secondary reactions the borohydride and dimethylamine borane oxidation in 3 M NaOH solution shows, respectively, a four- to six-electron process and a four- to five-electron process in direct fuel cells. The direct oxidation of the borohydride exhibits a peak at about −0.07 V versus Ag/AgCl, while the dimethylamine borane peak is at about −0.03 V versus Ag/AgCl. For the 0.04 M concentration the borohydride displays a power density of 31 W m −2 which is 16% higher than that of the dimethylamine borane.