Fuel cells based on the use of Pd foils

In this work, an alkaline fuel cell (AFC) with a Pd-based hydrogen diffusio n anode in combination with a carbon-PTFE oxygen diffusion cathode has been built up and tested at low temperatures. The anode was a 25 mu m-thick Pd foil with electrodeposited Pd black by one or by the two sides. It was asse mbled to the cell holder by means of elastic joints to allow the Pd foil cr easing necessary for a quasistationay operation. Experiments with different electrode sections indicated that the anode was the limiting electrode. Th e limiting process when Pd black was present only at the Pd/electrolyte int erface was probably the atomic hydrogen diffusion over the gas/Pd interface between the adsorption sites and the predissolved-state sites. When Pd bla ck was present only at the gas/Pd interface or on both sides of the foil, o ne of the slowest reactions appeared to be hydrogen adsorption on the gas/P d interface. The maximum anode power density for Pd foils with Pd black on both sides were about 11 and 18 mW cm(-2) at 25 and 50 degrees C, respectiv ely, corresponding to anode current densities of about 30 and 65 mA cm(-2). Much greater anode power and current densities were achieved for Pd pieces charged cathodically with atomic hydrogen and for Pd foils with electrodep osited Pd+Pt blacks. For these latter foils, a maximum anode power density of 65 mW cm(-2), corresponding to a current density of 120 mA cm(-2), was o btained.