J. Jindra

Carbon electrodes with phthalocyanine catalyst in acid medium

The catalytic properties of polymeric phthalocyanines with Fe and Co as central atoms for the electroreduction of oxygen in 0.5–2.3m H2SO4 were studied. No noticeable dependence of the electrode potential on the concentration of H2SO4 was found. The electroactivity of the catalyst with a central Fe atom undergoes considerable deterioration under the given conditions, whereas the stability of the catalyst with a central Co atom is very good and the potential of an electrode containing 30% catalyst in the active mass is 100 mV more positive than that of an electrode with 13% platinum, both at 40 mA cm−2. The electrode performance depends markedly on the sort of carbon substrate, showing a parallelism with respect to oxygen electrodes in alkaline medium. The gold mesh current collector can be replaced by the addition of carbon black to the active layer.

Zinc-air cell with neutral electrolyte

The zinc-air electrochemical system in 5m NH4Cl was studied. The optimum electrolyte-zinc ratio was found to be 50 ml g−1 Zn and the optimum electrolyte-cathode ratio, 15 ml cm−2 of carbon cathode. The air cathode polarization is not increased by intermittent usage of the cell. Electrodes made from zinc sponge with addition of lead show the smallest corrosion in the given electrolyte. The cell voltage is about 0.9–0.95 V at a load of 10 mA cm−2 of carbon cathode at ambient temperature.

Impedance characteristics of sealed lead/acid cells during galvanostatic charge

Abstract The electrochemical impedance of a model hermetic lead accumulator and its electrodes was measured during continuous or interrupted charging either in potentiostatic (at 10 4 -10 −3 Hz) or in galvanostatic (at 0.1 Hz) mode. The impedance characteristics of the negative electrode changed considerably during the second half of charging and during overcharging. The impedance curve at 0.1 Hz measured during continuous galvanostatic charging can be used to indicate the state of full charge of the cell.

Oxygen cycle in sealed leadacid batteries

Abstract This review is concerned with problems associated with the evolution of hydrogen and oxygen and their ionization in sealed leadacid batteries. The roles of the separator and of admixtures in the battery constituents are discussed in detail, and the possible applications of the batteries are briefly evaluated.

Study of sealed lead/acid cells

Abstract Based on barodynamic characteristics, both the oxygen pressure and the oxygen reduction current at the negative electrode in a sealed lead/acid cell were followed. These data together with potentiodynamic characteristics were used to characterize the time course of the oxygen cycle and its efficiency. Data about the partial pressure of hydrogen were also obtained and experimentally verified. Calculations were made on the assumption that at the positive electrode only oxygen is evolved and at the negative electrode only hydrogen evolution and oxygen reduction proceed.

Plastic-bonded electrodes for nickel—cadmium accumulators. VIII. Study of oxygen recombination rate on plastic-bonded cadmium electrodes provided with active carbon catalyst☆

Abstract The oxygen recombination (reduction) rate on plastic-bonded cadmium electrodes in sealed NiCd systems can be controlled by the use of a catalytic mix consisting of active carbon and carbon black either in the pure state or mixed with PTFE. This catalytic mix is either rolled onto the gas side of the plastic-bonded cadmium electrode or added to the active material prior to the preparation of the electrode by a rolling technique. The highest oxygen recombination rate, which surpassed that obtained with commercial pocket-type electrodes, was obtained in both cases by the use of an active carbon, carbon black and PTFE catalytic mix. In this case an optimum three-phase boundary, well known from oxygen electrodes for fuel cells, was established.

Oxygen recombination rate on plastic-bonded cadmium electrodes doped with nickel(II) hydroxide

Abstract It was found that the rate of reduction of oxygen on plastic-bonded cadmium electrodes doped with Ni(OH)2 is highest when the added nickel amounts

ESCA investigations on plastic-bonded nickel oxide electrodes

Abstract Electrode samples, prepared by a rolling technique from an active mass, graphite and Teflon mixture, were characterized by ESCA (X-ray photoelectron spectroscopy) before operation, after a short electrochemical formation, and after a certain number of charge—discharge cycles. The spectra of F 1s , C 1s , O 1s and Ni 2p 3/2 were measured in detail. A splitting of the F and C signals (from Teflon) in the Teflon—graphite mixture was interpreted as indicating different qualities of contacts between the Teflon and graphite particles. The change in character of this contact resulting from cycling of the electrode was followed and was considered to be the cause of the change of the electric resistance in the electrode. From the decrease of the intensity of the Ni signal one can conclude that part of the Ni(OH) 2 /NiO(OH) system withdraws from the surface of the graphite particle structure during prolonged operation of the electrode. This effect is caused by a partial crystallization of the hydrated Ni(II)Ni(III) oxide system which, in its turn, causes discontinuities in the hydrogel to appear, reflected by an increase in the F 1s signal intensity.

Plastic-bonded electrodes for nickel-cadmium accumulators: IX. Oxygen recombination rate on plastic-bonded cadmium electrodes with different active materials

Abstract The rate of oxygen recombination ( i.e. , reduction) on plastic-bonded cadmium electrodes in sealed NiCd systems can be controlled over a wide range by doping the negative active material with Ni(OH) 2 , Fe 3 O 4 or carbon black. The highest recombination rate was attained by combining all these additives (treatment of CdO with Ni(OH) 2 and subsequent addition of Fe 3 O 4 and carbon black), allowing the plastic-bonded electrodes obtained to be used without further modifications in sealed NiCd systems.

Protection of sealed NiCd cells from cell voltage reversal: I. experimental conditions for the formation of cadmium bridges

Abstract A common polyamide separator, used as the electrolyte carrier in sealed Ni/Cd cells, can also function as a carrier for the Cd/Cd 2+ system, the deposition method being the same as that in the preparation of sintered Cd electrodes. A separator thus treated is suitable for sealed Ni/Cd cells. If it is cycled at least once in an excess of alkaline electrolyte prior to sealing, and if the cell capacity is limited by the positive electrode, the explosion hazard of the sealed cell due to voltage reversal can be eliminated by a proper choice of separator and cadmium loading. Cadmium bridges formed in the separator under these conditions prevent gas formation on either electrode, their properties depending on the quality of the separator and its loading with cadmium.