The use of channel flow cells for electrochemical kinetic studies in high temperature aqueous solutions

Abstract

It has been shown that, for the case of one-step reactions of arbitrary order, the relationship between the average current density and the limiting current density on a working electrode mounted on the inner radius of an annular flow channel of arbitrary length obeys, with great accuracy, the same relations as does a reaction on a uniformly accessible surface. This allows us to combine the advantages of non-uniformly accessible surfaces (high sensitivity, and no need to use rotating contacts) with the advantages of uniformly accessible surface systems (simple treatment of experimental data). This feature can be very important when investigating systems at high temperatures and pressures, where RDEs are difficult to employ. Using this approach, and by employing previously measured polarization data, the kinetic parameters (exchange current density and anodic transfer coefficient) for the oxidation of hydrogen on platinized nickel in 0.1 M NaOH + 0.7 × 10 −3 m H 2 at temperatures between 25 °C and 300 °C have been derived. The anodic transfer coefficient is found to be almost temperature independent with a value of 0.43. The exchange current density displays Arrhenius behavior with temperature, increasing from 1.9 × 10 −4 A cm −2 at 25 °C to 3.9 × 10 −3 A cm −2 at 300 °C.