ELECTROCHEMISTRY OF FUEL CELL ELECTRODES. HYDROGEN OVERVOLTAGE AT A DROPPING THALLIUM AMALGAM ELECTRODE.
TYCO LABS INC WALTHAM MA
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Measurements were made of hydrogen overvoltage, in 0.1 M HClO4, at temperatures from 14 to 69 C, at dropping amalgam electrodes containing 10.0 and 40.6 mole percent thallium. The overvoltage was 20 to 30 millivolts higher on 40 Tl amalgam than on mercury. When corrections were made for the effect of the diffuse double layer, the exchange current for hydrogen discharge at 25 C was found to decrease by a factor of 2 on going from Hg to 40 Tl amalgam. The temperature dependence of overvoltage gives an enthalpy of activation extrapolated to the reversible hydrogen potential of 22.3 0.4, 21.2 1.1, and 23.1 0.3 kcalmole for Hg, 10 Tl amalgam, and 40 Tl amalgam respectively. Thus, both the overvoltage and the enthalpy of activation are higher on Tl amalgams than on Hg. Author