топливный элемент

DOI: 10.18500/1608-4039-2015-15-4-175-179

The reasons, that lead to the performance loss of alkaline matrix electrochemical generator (ECG) based on hydrox cell and therefore reduce the fuel cell stack cycle life, are highlighted in this article. It is shown that storage of ECG, preserved with a special gas mixture within up to 20 years, doesn't lead to noticeable characteristic fluctuation.

В работе рассмотрена металлизация электролитной матрицы щелочного матричного топливного элемента, обусловленная растворением платинового катализатора на кислородном электроде этого элемента. Показано, что уровень металлизации зависит от условий функционирования топливного элемента и структурных особенностей его составляющих.

The work reviews the influence of gas impurities in fuel and oxidizing chemical on the alkaline oxyhydrogen fuel cell functioning. It shows that methane impurities act differently on anode and cathode, while other gases (except noble gases), including carbon monoxide, which is a poison for fuel cell with acid solution, influence the operation of alkaline fuel cell through the reaction with potassium hydroxide (KOH). Substitution electrolyte for fresh recovers fuel cell performance.

Using complex models, including the solution percolation problem and electrochemical kinetics calculations are considered the features of a solid polymer fuel cell catalyst layers with a catalyst based on nanoscale carbon materials, including graphene nanowires. These calculations are consistent with the experimental data presented by optimizing the composition of the catalyst layers. It is shown that the addition of 20 wt.\% nanofibres graphene can reduce ohmic losses from the ion current and improve the performance of the fuel cell is 20%

Composition and structure of proton-exchange membrane fuel cell catalytic layers were investigated. Modelling of catalytic layer vas considered. This model allows to calculate layers containing particles of polymer and the catalyst of various forms and sizes. Dependence of conductivity and active layer surface area on concentration of polymer particles is shown. Best performance of a fuel cell is observed at the polymer concentration in a layer of 30–35% vol.

Concentrated water-alkaline mixtures of sodium and potassium borohydrides and borates are used as fuel and a hydrogen source in hydrogen power engineering, including low-temperature fuel cells. The performance of such mixtures is determined by their physicochemical properties. An algorithm to calculate the density, viscosity, and specific electric conductivity of mixed solutions of the five-component water + salt system (Na,K)BH₄ + (Na,K)BO₂ + (Na,K)OH + H₂O based on the quasiadditivity of these properties is proposed. The concentration-temperature dependences of the density, viscosity, and specific conductivity of aqueous KOH, NaOH, KBO₂, NaBO₂, NaBH₄, and KBH₄ solutions of any composition in a temperature range of (0 to 60)°C and the whole concentration range are described mathematically. The technique and algorithm of calculation have been verified by comparison with measured properties.

Composition and structure of proton-exchange membrane (PEM) fuel cell catalytic layers were investigated. The maximum FC efficiency was observed at the polymer content in a layer 25-30 vol.% at work on air and 30-35 vol. % at work on oxygen. At a variation of quantity of catalytic composition the maximum current density have been received at layer load 1.75 mg/sm², thus decrease in it value in 2 times leads to falling of current density only on 10%.

A model connecting the weight, volume, and chemical changes of heterogeneous borohydride fuel occurring at discharge of the direct borohydride fuel cell is presented. The experimental data measured with a fuel on the basis of water-alkaline solution of potassium borohydride KBH4 at temperature 25°C arc compared with theoretically calculated curves. Good conformity is acknowledgement of the 8-electron mechanism of borohydride ion oxidation.

Electrochemical activity of anodes on the basis of a nickel mesh grid for water electrolysis is investigated. Activation of anodes was made by three ways:
1) chemical covering sulfur-containing compounds of nickel and iron;
2) immersing in solution Na₂S₂O₃ + H₂SO₄ (till pH=3);
3) immersing in solution Na₂S + H₂SO₄ (till pH=3).
The water solution 6M KOH was used as the electrolyte while the electrodes testing. Current density varied in a range from 1 to 600 mAJ cm2 at temperature 20, 50 and 70°C. The greatest electrochemical activity have anodes activated by the third method. The anode potential at current density 600 mA/cm² and temperature 70°C is equal +0.57 V (concerning Hg/HgO – the comparison electrode).

In the current paper electrospun nanofiber mats were derived from polyacrylonitrile (PAN). The temperature influence on the volumetric and surface composition of the resulting pyropolymers was studied by means of elemental analysis and X-ray photoelectron spectroscopy. Rotating disc electrode (RDE) and rotating ring disc electrode (RRDE) methods were used to determine the catalytic properties of PAN pyropolymers, derived at carbonization temperature interval of 600–1200°C, as well as composite PAN/support catalysts, carbonized at 900°C, in the oxygen reduction reaction in H₂SO₄ и KOH solutions. The methods of cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic polarization were utilized to characterize the charge capacitive properties. An equivalent scheme modeling the electrochemical response of PAN pyropolymer in H₂SO₄ solution was proposed. An assumption was made of interrelation between the PAN-T catalytic activity and the occurrence of condensed parquet aromatic structure comprising of nitrogen-carbon bonds. Evidence was given that Fe atoms play the key role in the synthesis of active non-precious catalysts with high selectivity towards the 4-electron O₂ reduction. The possibility of the catalysts synthesis for 2-electron ORR without the use of metal precursors was evidently shown. Prominent correlation of capacitive and catalytic properties for these materials was observed in H₂SO₄ solution. The optimal PAN pyropolymers synthesis temperature was determined to be in the range of 750–950°C. The mats of PAN-T were shown to be feasible as the negative electrodes of supercapacitors.