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In alkaline hydrogen-oxygen fuel cells Raney nickel is employed as catalyst for hydrogen electrodes. The rate of anodic hydrogen conversion has been increased significantly by using a titanium-containing Raney nickel. The properties of the catalyst powder, the influence of particle diameter, and the behavior of electrodes under load are described. Impedance measurements have been used to characterize the electrodes. In fuel cell systems the supported electrodes are normally operated at current densities up to 0.4 A'cm-2; the overload current density of 1 A.cm -~ can be maintained for several hours.The economic factors of the H2-O2 fuel cell are determined essentially by the costs of the catalysts employed in the electrodes. Hence it is rational for commercial applications to avoid the expensive and rare materials such as noble metals. In alkaline electrolyte, the metals nickel and silver are suitable as catalysts for the anode and the cathode, respectively (1, 2). Catalyst powder with large interior surface is used to have a large reactive surface area available. Raney nickel has thus proved useful for the H2 electrode (2) and it is considered in detail. The active material can be depyrophorized by a slow surface oxidation and the catalytic activity could be increased by annealing at 300~ in hydrogen atmosphere (3). The attainable current density of the electrodes depends strongly on the pretreatment of Raney nickel (2, 4).A further increment in catalytic activity could be achieved by changing from a binary Raney alloy to a ternary system in which an additional metal such as iron, molybdenum, or titanium has been alloyed to nickel and aluminum (5-7). The objective of the alloy additives is to produce ternary phases in which Ni, A1, and the additive metal are distributed homogeneously. Only such phases yield homogeneous alloy catalysts with highest activity. The additive metals lead to a lower filling of d bands and to lattice defects.The properties of titanium-containing Raney nickel catalyst are reported here. ExperimentalPreparation of the cataIyst.~The Raney alloy has a mass fraction of 50% A1; the rest consists of Ni and Ti in which the titanium content can be varied from 0 to 5%. When the liquid alloy is quenched in a water bath titanium remains dissolved in the two compounds NiA13 and Ni2Ala. A granulate is formed which can be powdered easily in a mill. Powder with a particle diameter of less than 50 ~m is employed.Aluminum is extracted to an extent of 95% in 6M potassium hydroxide at 80~ titanium remains completely in the catalyst. After washing, the powder is dried in vacuum and subjected to surface oxidation by

Animal experiments with biogalvanic cells have demonstrated that an average power of 80 muW can be derived continously for at least 2 years. There is a further scope to stabilize the power at 100 muW for considerable longer periods so that the chances of cardiac pacing with biogalvanic power have become bright. However, large scale efforts are necessary in in establishing the statistical reliability and the secured performance which are expensive and time consuming. Animal experiments with biofuel cells are still in preliminary stages. We derived a continous power of 40 muW (4MUW/cm2) at 575 mV over 150 days so far. This is the longest recorded period with such a high power density. The main problem in deriving higher power over longer period is to properly encapsulate the cell with materials which are hydrophilic and essentially biocompatible.

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Auf Grund reaktionskinetischer Untersuchungen konnte die Struktur der Eisen‐Elektrode so abgeändert werden, daß Stromdichten von 40 mA/cm2 bei 40‐ bis 50‐proz. Ausnutzung der aktiven Masse über mehr als 100 Zyklen möglich sind. Die Kapazität der Elektroden sinkt im Temperaturbereich von + 25 bis 0°C von 5,5 auf 3,5 Ah ab. Bis zu Ladeströmen von 100 mA/cm2 bleibt die entnehmbare Kapazität konstant. Maximale Kapazität wird bei einem Überladefaktor von 1,6 erreicht. Bei von 20 auf 200 mA/cm2 steigenden Entladestromdichten sinkt die Elektrodenkapazität von 0,287 auf 0,075 Ah/cm2 ab. Der Entladeendpunkt beeinflußt stark die Kapazität der Elektroden. Eine unverminderte Überlastbarkeit der Elektroden bis zu 150 mA/cm2 ist noch nach der Abgabe der halben Ladung zu erwarten.