Active layer of fuel cell electrode with polymer electrolyte: Modeling of support grains, calculation of overall cathode characteristics

The active layer of the cathode of a fuel cell with polymer electrolyte (Nafion) is considered. The optimum carbon support structure is constructed using computer simulation: its carbon “skeleton” possesses the maximum outer surface area and provides electronic conductivity of the grains, support cubes, along the three coordinate axes. Nafion is absent in the support grain, so that the grain is capable of participating only in the transport of oxygen molecules, it possesses no proton conductivity. An estimate of all parameters of an optimum support grain is provided; in particular, the value of the effective Knudsen diffusion coefficient of oxygen is established. After this, effective proton conductivity and effective Knudsen diffusion coefficient are calculated already on the whole active layer scale, according to the model of equally sized cube grains of three types. In conclusion, the overall current in the active layer of a cathode with a polymer electrolyte was calculated for the percolation cluster consisting only of Nafion grains and the Knudsen diffusion of oxygen created only by a combined gas percolation cluster consisting of void grains and all support grains. The overall current value for t = 80°C and pressure of p* = 101 kPa proved to be low, hundreds of mA/cm². The current value can apparently be increased to several A/cm² if the support grains are developed that would simultaneously possess both proton conductivity and ability to sustain oxygen diffusion.     

Computer simulation of active layer of fuel cell electrode with polymer electrolyte: Complete combined carbon support grains, calculation of overall characteristics

Full computer simulation of the active layer of a fuel cell cathode with polymer electrolyte and complete combined carbon support grains is carried out. The active layer structure included two types of equal-size cubic grains (combined support grains and voids) together forming a cubic lattice. Also, the structure of combined grains was modeled; a carbon cluster was formed in them, with the oxygen reduction process occurring on its surface; the rest of the grain volume was filled by polymer electrolyte. The completeness of the grains consisted in the fact that they were characterized by 3D electron conductivity, ability to take part in the transport of protons in the active layer and the carbon cluster in the grains had the maximum possible surface area. Calculation of overall currents of oxygen cathodes with full combined carbon support grains, Nafion, and platinum yielded the following result. At t = 80°C, pressure p* = 101 kPa, cathode potential E ₀ = 0.8 V, and optimum active layer thickness Δ* = 20 μm, maximum overall current I _max = 0.38 A/cm², maximum power density W _max = 0.31 W/cm². At potential E ₀ = 0.7 V, Δ* = 9.8 μm, I _max = 1.13 A/cm², W _max = 0.79 W/cm². At potential E ₀ = 0.6 V, Δ* = 3.8 μm, I _max = 2.95 A/cm², W _max = 1.76 W/cm². At potential E ₀ = 0.5 V, Δ* = 1.4 μm, I _max = 7.71 A/cm², W _max = 3.86 W/cm². The overall current values are higher than those observed experimentally at the given cathode potentials. The discrepancy is explained by the fact that calculations of active cathode layers with a practically regular structure were carried out. All combined support grains in them are full and identical, while in fact the active layer structure is not characterized by the properties of fullness and equivalence. The second circumstance is that experimental active layers rarely have a strictly optimum thickness. Meanwhile deviation from this optimum results in losses in current. Transition to cathodes with combined grains has additional advantages. (1) In such grains, all platinum participates in current generation, the catalyst utilization degree reaches 100%. (2) Oxygen can enter the active layer not through small Knudsen pores, but through large (with the diameter of hundreds and more nm) gas pores, in which usual molecular gas diffusion occurs, so that diffusion limitations in the active layer become less significant. 3. In the active layer, the danger of gas pore flooding by evolving water decreases. Now, water vapor is much more easily removed from large gas pores directing then into the gas-diffusion layer pores.     

Alkaline fuel cells: Calculating and comparing overall currents of hydrophobized cathodes with thin regular-structure and thick stochastic-structure active layers

A concept of active hydrophobized active layers with regular structure is introduced. In these layers, a hydrophobizer takes part in the development of gas pores representing a set of straight identical rods (cylinders) uniformly distributed over the active layer and extended in a direction perpendicular to the cathode surface. An advantage of cathodes with a thin regular-structure active layer is the reproducibility of their characteristics and a low content of platinum catalyst (up to tenth and even hundredth fractions of mg/cm²). A comparison of current characteristics of thin (with the thickness of several tens of μm) active layers with a regular structure and thick (with the thickness of several hundreds of μm) with the stochastic distribution of the hydrophobizer (with randomly distributed polytetrafluoroethylene) is made. For a fuel cell with an alkaline electrolyte (7 M KOH at 60°C), calculations show that at potentials below 0.5 V (RHE), the cathodes with thin regularstructure active layers demonstrate higher overall currents as compared with cathodes covered with thick active layers with a stochastic structure. However, the opposite trend is observed at potentials above 0.5 V. To increase the current in cathodes with thin regular-structure active layers, it is possible to, first, increase the active layer thickness and, second, decrease the size of hydrophobizer grains in them.     

Cathodic active layer in a polymer electrolyte fuel cell: Model of combined grains,calculation of overall characteristics

A new type of the cathodic active layer structure for a polymer electrolyte fuel cell is proposed. This structure is based on combined grains and gas pores. Combined grains represent nonporous agglomerates of carbon black particles (catalyst carrier) and Nafion molecules. This type of cathodes has the following advantages: (1) in combined grains, complete utilization of the catalyst occurs, (2) limitations on the oxygen delivery into the active layer are almost totally lifted, and (3) the danger that pores will be flooded with evolved moisture is actually released. The overall characteristics of cathodes with combined grains are calculated. The advantages of such oxygen or air cathodes are demonstrated, namely, not only their enhanced power density but also the lower index of platinum consumption, i.e., the platinum amount per kW of electric energy produced in the membrane-electrode block, as compared with conventional cathodes.     

Effect of Temperature on the Catalytic Ability of Electrochemically Active Biofilm as Anode Catalyst in Microbial Fuel Cells

In this study we report the effect of temperature on the catalytic ability of an electrochemically active biofilm based on mixed‐culture to oxidize acetate and found the optimum temperature showing maximal catalytic activity and power output. Electrochemical characterization of biofilm and power output and internal resistance of microbial fuel cell (MFC) have been investigated at different temperatures. When temperature increased from 30 to 45 °C the catalytic ability of biofilms to oxidize acetate increased following the Arrhenius law with apparent activation energy of 44.85 kJ/mol. At temperatures higher than 48 °C, however, the bioelectrocatalytic current decreased. At 53 °C the bacterial metabolism was in inactivation. The optimum working temperature of the biofilm was 45 °C, producing current of 1339 µA cm^?2. This current was almost three times higher than 527 µA cm^?2 at 30 °C. The MFC performance at different temperatures showed consistent temperature dependence to that of a semi‐batch cell, which implies that anode catalytic ability in MFC is the main limit factor for increasing power output. A maximum power output of 1065 mW m^?2 was also observed at 45 °C and it was 1.5 times higher than 764 mW m^?2 at 30 °C. The increased MFC performance from 30 °C to 45 °C is lower in comparison with about three times higher increase in semi‐batch cells. This could be due to other factors such as proton migration rate in membrane of MFC, which can be seen from that the internal resistance value of 121.5 Ω in the MFC at 45 °C was only slightly lower than 177.6 Ω at 30 °C. Also, some other factors such as cell configuration which would limit the power output and can be further optimized. This work contributes to the study of influence from temperature on anodic electrochemically active biofilm activity and their subsequent influence on MFC performance and reports the optimal temperature for biofilm activity based on mixed‐culture.     

Solid oxide fuel cells with film electrolytes prepared by chemical vapor deposition

Basing on the developed film formation technique by organometallic chemical vapor deposition (organometallic CVD), thin films of electrolytes were prepared on supporting anode and experiments were carried out to optimize the cathodic layer forming conditions. The individual electrochemical cell achieved the specific power of 1190, 800, and 350 mW/cm² at the temperatures of 800, 700, and 600°C, respectively. Operation of a 13 cm² fuel cell in solid oxide fuel cell (SOFC) battery was studied.     

Effects of humidity and temperature on the electrochemical activities of H2/O2 PEMFCs using hybrid membrane electrolytes

Electrochemical characteristics of single cell performances at various humidity conditions and constant temperatures of 40?100 °C using membrane electrode assemblies (MEAs) were studied. The MEAs consist of alternative proton-conducting hybrid membrane electrolyte and noble Pt/C catalyst for the H₂/O₂ proton exchange membrane fuel cells (PEMFCs). The function of humidity on the cell performances was investigated at larger current density values of 501 mA cm^?2 and constant cell temperatures of 80 and 90 °C and the relative humidity of 100 %. The power density value of 400 mW cm^?2 was obtained when the same MEA at similar operating conditions was used. The effects of temperature on the single cell performances were investigated at various temperature ranges of 40–100 °C and constant relative humidity of 50, 70, and 100 %. The maximum current density and power density values of about 600 mA cm^?2 and 160 mW cm^?2, respectively, were obtained at 90 °C with 100 % RH. The results were compared with the reported results of Nafion membrane and similar hybrid membranes operating at low temperatures for H₂/O₂ fuel cells. Finally, the results provided an alternative proton-conducting electrolyte as promising candidate for low/intermediate temperature operating H₂/O₂ fuel cells.     

Reversible Solid Oxide Fuel Cell for Power Accumulation and Generation

The anodic and cathodic polarization dependences for the oxygen electrode based on lanthanum-strontium manganite and the fuel Ni-cermet electrode are studied in the temperature range of 700–900°С in gas media that correspond to working conditions of a reversible fuel cell. The temporal behavior of these electrodes is studied in the course of periodic polarity changes of current with the density of 0.5 A/cm². The electrode overvoltage is shown to be about 0.1 V in modes of power generation and water electrolysis at 900°С and the current density of 0.5 A/cm². A single electrolyte supported tubular solid-oxide fuel cell was fabricated and tested in the fuel-cell and hydrogen-generation modes. It is found that at 900°С and overvoltage of 0.7 V, the cell generates the specific electric power of 0.4 W/cm² when the 50% H2 + 50% H₂O gas mixture is used as the fuel and air is used as the oxidizer. At the water electrolysis with the current density of 0.5 A/cm², which under normal conditions corresponds to generation of about 0.2 and 0.1 L/h of hydrogen and oxygen, respectively, the consumed power is about 0.55 W/cm². The efficiency of the conversion cycle electric power–hydrogen–electric power is 70–75%.     

A direct-methane solid oxide fuel cell with a double-layer anode

A tubular anode-supported solid oxide fuel cell with a double-layer anode for the direct conversion of CH₄ has been prepared and operated at 800 °C successfully. The double-layer anode was composed of NiO–YSZ and CoO–NiO–SDC acting as supporting layer and active reforming layer, respectively. At 800 °C, a maximum power density of 350 mW cm⁻² was obtained with CH₄ as fuel and air as oxidant. The time-dependent impedance spectra of the tubular cell were examined and discussed. No carbon deposition was observed on the surface of the anode when the cell was operated at a constant current density of 250 mA cm⁻².     

Preparation and electrochemical characterization of Ruddlesden–Popper oxide La4Ni3O10 cathode for IT-SOFCs by sol–gel method

La₄Ni₃O₁₀ oxide was synthesized as a cathode material for intermediate-temperature solid oxide fuel cells by a facile sol–gel method using a nonionic surfactant (EO)106(PO)70(EO)106 tri-block copolymer (F127) as the chelating agent. The crystal structure, electrical conductivity, and electrochemical properties of La₄Ni₃O₁₀ were investigated by X-ray diffraction, DC four-probe method, electrochemical impedance spectra, and I–V measurements. The La₄Ni₃O₁₀ cathode showed a significantly low polarization resistance (0.26 Ω cm²) and cathodic overpotential value (0.037 V at the current density of 0.1 A cm^?2) at 750 °C. The results measured suggest that the diffusion process was the rate-limiting step for the oxygen reduction reaction. The La₄Ni₃O₁₀ cathode revealed a high exchange current density value of 62.4 mA cm^?2 at 750 °C. Furthermore, an anode-supported single cell with La₄Ni₃O₁₀ cathode was fabricated and tested from 650 to 800 °C with humidified hydrogen (～3 vol% H₂O) as the fuel and the static air as the oxidant. The maximum power density of 900 mW cm^?2 was achieved at 750 °C.     

Calculation of optimum thickness of active layer of oxygen and air cathodes of fuel cell with Nafion and platinum

It is shown that, for the electrodes of fuel cells with solid polymer electrolyte, the dependence of overall current on the active layer thickness contains an extremum. There is an optimum thickness of active layer, at which the overall current reaches its maximum possible value. The nature of this dependence is explained. The character of the distribution of electrochemical process intensity over the depth of active layer of cathode with solid polymer electrolyte is analyzed. The optimum thicknesses of active layers of oxygen and air cathodes of fuel cells with Nafion and platinum and the corresponding overall currents and contents of catalyst in the active layer are calculated. In the calculations, the temperature of fuel cell, the pressure in the cathode gas chamber, and the cathodic potential were varied. The optimization of active layer thickness of cathode with solid polymer electrolyte can reduce the platinum consumption, i.e. its amount per 1 kW of power produced in a membrane-electrode assembly.     

Computer simulation of negative electrode operation in lithium—ion battery: Galvanostatic discharg active intercalating agent grains,role of diffusion limitations

Computer simulation of the structure and methods of operation (galvanostatic discharge) of the negative electrode of a lithium-ion battery is performed. Two possible models of the active anode layer were compared. 1. The model of porous active layer (mixture of active substance grains with grains of electrolyte). Here, the electrochemical process occurs within a porous active layer. 2. The film model (constant-thickness layer) of pure active substance (intercalating agent) grains without admixture of grains of electrolyte. In this case, the electrochemical reaction occurs only on the planar active electrode layer/interelectrode space interface. In both cases, the optimum working parameters of anode active layers were calculated: porous active layer thickness (in the film model, this was the calculation parameter), duration of full anode discharge, specific electric capacitance and finite difference between the intercalating agent/electrolyte potentials at the active anode layer/interelectrode space interface. It is found that each of these two models has its advantages and faults. Specific electric capacitance C cannot exceed the values of the order of magnitude of 10 C/cm² when a porous active layer is used. Whereas in the film model, much higher values of C may be obtained: tens and even hundreds of C/cm². On the other hand, in the case of anode discharge, the reasonable discharge current density value, its maximum value, at which practically full recovery of lithium atoms from active intercalating agent grains is still possible, proves to be by orders of magnitude higher in the case of an anode with a porous active layer, as compared with a film-type anode. Thus, in the case of development of electrode active layers of lithium-ion batteries, there is a possibility of choosing from two variants. There is the variant of an active film-type layer providing high capacitance values, but low discharge current density. Or there is another variant: a porous active layer with limited capacitance but then much higher values of discharge current density.     

Micro-tubular solid oxide fuel cells fabricated by phase-inversion method

A novel structured micro-tubular solid oxide fuel cell (MT-SOFC) has been fabricated by combining a phase-inversion, dip-coating and high temperature co-sintering process with impregnation of the electrode catalyst into a porous electrode matrix. The asymmetric porous anode made by phase-inversion is divided into two different layers, a thick fuel delivery layer with large finger-like pores and a thin function layer with small finger-like pores. The MT-SOFC demonstrates maximum power densities of 0.44, 0.54, 0.65 and 0.78 W/cm² at 650, 700, 750 and 800 °C, respectively with H₂–15%H₂O as fuel and ambient air as oxidant. Combining the power output with the quick start-up behavior, novel structured MT-SOFC offers a potential solution for rapid start-up high performance power devices.     

Cathode of a hydrogen-oxygen fuel cell with a solid polymer electrolyte: The effect of the flooding of pores by water on the characteristics of the active layer

A computer model of the active layer of the cathode of a hydrogen-oxygen fuel cell with a solid polymer electrolyte is studied. The active mass of the electrode consists of equidimensional grains of the substrate (agglomerates of carbon particles with platinum particles embedded in them) and a solid polymer electrolyte (Nafion). The flooding by water can be experienced by both the pores in the substrate grains, which facilitate the oxygen penetration into the active layer of the electrode, and the voids between the grains. All possible versions of the flooding of these pores by water are considered. A calculation of the optimum, at a given polarization of the electrode, value of electrochemical activity, the thickness of the active layer, and the weight of platinum is performed. The major parameters of the system are the concentrations of grains of the substrate and solid polymer electrolyte, the size of these grains, the platinum concentration in the substrate grains, the average diameter of pores in the substrate grains, and the polarization of electrodes. The ultimate aim of the work is to estimate how the flooding of pores of the active layer of the cathode by water affects the magnitude of the optimum current, the effective thickness of the active layer, and the weight of platinum.Translated from Elektrokhimiya, Vol. 41, No. 1, 2005, pp. 35–47.Original Russian Text Copyright © 2005 by Chirkov, Rostokin.     

Calculating a Characteristic Bulk Current Density in the Cathode of a Hydrogen-Oxygen Fuel Cell with a Solid Polymer Electrolyte

The magnitude of currents of electrodes in hydrogen-oxygen fuel cells of all types is shown to be fully determined by values of the effective coefficient of gas diffusion, the effective coefficient of ionic conduction, and the characteristic bulk current density. The characteristic bulk current density is estimated in two versions for cathodes with Nafion: the catalyst is distributed in the bulk of substrate grains or at their external surface. The currents commensurate with those observed in experiments are given only by the second version. Means of computer-aided simulation are used to imitate the formation of fractal films composed of the catalyst particles on the surface substrate grains. The simulation means made it possible to link the magnitude of the specific surface area of platinum particles with its weight content in substrate grains. Electrochemical characteristics of the cathode with Nafion-the potential dependence of the optimum magnitude of the overall current and the thicknesses of the active layer and the weight of platinum in it, as well as the magnitudes of the optimum current generated by a unit weight of platinum—are calculated. A notion of “ norm” is introduced for the characteristic bulk current density of the cathode. 1 × 10^?3 A cm^?3 is the electrochemical-process intensity, which the technology of preparation of active layers of cathodes can provide at this stage in the development of fuel cells with a solid polymer electrolyte.     

Transport properties of separating membranes MF-4SK during alkaline electrolysis of water

The transport properties of separating membranes MF-4SK are studied during electrolysis of H₂O in solutions of KOH. The effective diffusion coefficients of molecules of KOH and H₂O and the transfer coefficients of ions K⁺ and OH^? and molecules of H₂O are measured at KOH concentrations reaching 11 M, currents reaching 0.31 A cm^?2, at ambient temperature and at 80°C. In contact with a KOH solution in the concentration interval 0.1 to 11 M, the membranes that initially swelled in H₂O lose a considerable fraction of water that was present in them and the overall volume of clusters and solution-filled channels in them noticeably decreases. The coefficients of transfer by current of ions K⁺ out of anodic compartment into cathodic and the OH^? ions in the reverse direction, respectively, happen to be equal to about 0.6 and 0.4 at ambient temperature and 0.8 and 0.2 at 80°C. The coefficients of transfer of water molecules out of the anodic volume into the cathodic volume in the process of electrolysis happen to be in the limits 1.6–1.9 at ambient temperature and in the limits 2.2–2.8 at 80°C. The effective diffusion coefficients of molecules of KOH and H₂O at moderate concentrations of KOH (5.6 M) amount to ～2.6 × 10^?7 and 30 × 10^?7 cm²s^?1 at ambient temperature and ～4 × 10^?7 and 61 × 10^?7 cm²s^?1 at 80°C, respectively. At a high concentration of KOH (～10 M) these quantities substantially diminish.     

Effects of synthesis conditions on the electrochemical activity of titanium anodes with iridium oxide coating

The effects of temperature, heat treatment time, and iridium content in the active layer on the electrocatalytic activity of titanium anodes with active coating during oxygen evolution in 0.5 M sulfuric acid have been investigated. The highest activity of these electrodes is reached when the temperature of final treatment is 450°C, treatment time is 25 min, and iridium content in the active layer is over 2 g/cm². An X-ray photoelectron spectroscopy study showed that iridium is predominantly in the tetravalent oxidized state in the active layer.     

A cathode for solid polymer electrolyte fuel cells: Designing the optimal structure of the active layer

The complete computer simulation of the cathodic active layer with solid polymer electrolyte (Nafion) is carried out. The active layer structure can be described by 8 parameters. In designing the optimal structure, it is shown that to provide the high overall characteristics of the cathode and save the catalyst, 0.5 of the active layer volume should be set aside for the support grains (agglomerates of carbon particles covered with platinum and containing Nafion incorporations and microvoids). Protons and oxygen molecules must be supplied to the active layer by means of peculiar combined percolation clusters. The latter consist of a combination of support grains with either Nafion grains (to produce “protonic” clusters) or grains-voids (to afford “gas” clusters). The volume fractions of Nafion grains and grain-voids are assumed to be 0.25 and 0.25. The computer simulation of the support grain structure is also carried out. Their composition, i.e., the volume fractions of the carbon component (g _e), Nafion (g _ii), and microvoids (g _gg), is varied. The support grains play the key role in the active layer functioning. It is impossible to organize three full-value percolation clusters (electronic, protonic, and gas); hence, one has to have one or two combined clusters in the active layer. Thus the double load fells on the support grains. Their optimal structure should not only sustain the transport of protons and electrons in the active layer but also create the best conditions for the electrochemical process in each grain. The maximum current I _max (realized upon reaching the optimal active layer thicknesses Δ*) is calculated. The dependences of I _max and Δ* on the main parameters characterizing the support grains (g _e and g _ii) are analyzed. Here, two goals are sought: (1) to obtain the high currents, (2) to provide the low consumption of platinum per power unit. To solve the first problem, one has to work with high values of g _e. The second problem requires the opposite: the values of g _e must be minimal possible.     

Computer Simulation of the Cathode Active Layer in Hydrogen–Oxygen Fuel Cell with Polymer Electrolyte: The Nature of the Overall Current Variations

Full computer simulation of the cathode structure in hydrogen–oxygen fuel cell with polymer electrolyte is performed. Both transport, support grains (agglomerates of carbon particles onto whose surface Pt-catalyst is deposited), and the current generation in active layer are simulated. The active layer operation in potentiostatic mode is studied. The effect of variations of the active layer and the fuel cell temperature (T_s and Т, respectively) on the cathode overall current I and the support grain flooding with water is calculated. The changes in the temperature difference T_s–Т was shown for the first time, experimentally and by the simulation, to generate variations of I and the degree of the support grain flooding with water. In particular, with the increasing of T_s–Т the current I increased, whereas the support grain flooding with water decreased; and vice versa, with the decreasing of T_s–Т the current I drops down, while, the support grain flooding with water grows. An explanation of the phenomena is presented, which takes account of structure of the support grains in which О₂ reduction and Н₂О generation occur. There exist intrinsic channels for protons and О₂ molecules transportation to the catalyst. Water releasing in the support grains is able to fill partially or even entirely the gas pores through which oxygen is supplied to the platinum. As a result, the current generated in the support grains can drop down significantly; at the same time, the value of I also drops down. The degree of the support grainfilling with water is determined by two processes, namely, the flooding and draining. The source of flooding is the current generation; that of draining, the water saturated vapor diffusion and water filtration in nanopores. The lower cathode potential, the higher the flooding rate, whereas the water removal rate grows or drops down with the increasing of decreasing of the temperature difference Т_s–Т, respectively. Thus, the temperature difference variations naturally lead to those of the quantity I.     

Electrocatalysts and membrane for direct ethanol-oxygen fuel cell with alkaline electrolyte

Results of studies of anodic (RuNi/C) and cathodic (PtCo/C; CoN₄/C) catalysts, polybenzimidazole membrane, and membrane-electrode assemblies on their basis for alkaline ethanol-oxygen fuel cell are presented. It is shown that the anodic catalyst RuNi/C optimized in its composition (Ru: Ni = 68: 32 in atomic percent) and the metal mass on carbonaceous support (15–20%) is sufficiently effective with respect to ethanol oxidation; it is well superior to commercial Pt/C- and RuPt/C-catalysts when calculated per unit mass of the precious metal. The effect of electrolyte composition, electrode potential, and temperature on the CO₂ yield is studied by chromatographic analysis of the ethanol oxidation products. It is shown that the highest CO₂ yield (the process involves the C-C bond break) is achieved at low electrolysis overvoltage and elevated temperature. The mean number of electrons given up by C₂H₅OH molecule approaches 10 at temperatures over 60°C. The studied cathodic catalysts form the following series of their specific activity in the oxygen reduction reaction: (20 wt % Pt) E-TEK ≥ (7.3 wt % Pt) PtCo/C > CoN₄/C; however, in the presence of alcohol the activity series is reversed. On this reason fuel cell cathodes were prepared by using synthesized CoN₄/C-catalyst. For the alkali-doped polybenzimidazole membrane the conductivity and ethanol crossover were determined. A membrane-electrode assembly for platinum-free alkaline ethanol-oxygen fuel cell is designed. It comprised anodic (RuNi/C) and cathodic (CoN₄/C) catalysts and polybenzimidazole membrane. The period of service of the fuel cell exceeded 100 h at a voltage of 0.5 V and current of 100 mA/cm².