Gerhard Dr Richter

Titanium‐Containing Raney Nickel Catalyst for Hydrogen Electrodes in Alkaline Fuel Cell Systems

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/sup -2/; the overload current density of 1 A . cm/sup -2/ can be maintained for several hours. (15 fig.)

Animal experiments with biogalvanic and biofuel cells.

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.

Electrochemical Properties of Platinum, Glassy Carbon, and Pyrographite as Stimulating Electrodes

Presently, platinum, platinum‐iridium, and carbon (glossy and pyrographite) are the preferred materials to be used as stimulating electrodes. Electrochemical tests revealed higher thresholds with Pt‐Ir, which possibly are a result of excessive connective tissue growth. A porous structure appears to be preferred especially if the electrode materials are smooth and activated glassy carbon. When comparing power consumption, glassy carbon was found to be a superior electrode material.

Equivalent circuit diagram and power consumption of stimulating electrodes

Abstract In order to compare different stimulating electrodes for cardiac pacemakers, impedance measurements have been carried out in physiological saline solution. Classical circuit diagrams are not able to describe the results. The impendance Z with reference to its frequency dependence can be expressed by the equations Z = Z1(ν/ν1x, where α = const. = (π/2)x. As an example of a porous electrode, a sintered tantalum electrode has been investigated; its behaviour is characterized by the volume capacity and the diaphragm resistance. In vitro and in vivo measurements have been compared. Stimulating electrodes were implanted in a cat and the threshold of the muscle was measured. The impedance of the Pt-Ir electrode had changed during the implanted period. Connective tissue had grown in the porous system of a sintered Ta-electrode. Porous electrodes are superior to smooth ones as far as the economic utilization of energy is concerned.