Electrode Kinetics for Chlorides of Tungsten, Antimony, and Phosphorus

Chronopotentiometry has been utilized to measure the rate constants for the first electroreduction step at platinum in dimethylformamide solution of several chlorine compounds of interest for regenerable fuel cell systems. The chronopotentiometric curves were also used to determine the diffusion coefficients and the products of the transfer coefficients with the number of electrons involved in the rate‐determining steps. Tungsten hexachloride obeyed the chronopotentiometric equation of reversible reactions, with an (vs. a gold reference electrode) for its one‐electron first reduction step. The reduction of to was irreversible and occurred in two steps, suggesting the intermediate formation of . The reductions of phosphorus chlorides and several group IV A chlorides were also found to be irreversible. Some correlation was noted between bond energies and the reciprocals of the rate constants. The electrode surface‐area requirements for minimizing activation polarization for and were calculated from the rate constants and chronopotentiometric data. Using Latimer's method, it was estimated that the fuel cell could produce 40% higher open‐circuit voltage than the fuel cell.