HYDROGEN OVERPOTENTIAL ON PLATINUM.
CASE-WESTERN RESERVE UNIV CLEVELAND OHIO ELECTROCHEMISTRY RESEARCH LAB
Pagination or Media Count:
Hydrogen electrode kinetics have been examined in Pt in HCl solutions over a large range of anodic and cathodic current densities using several techniques rotating disc-ring, cyclic linear sweep voltammetry, interrupter, and pulse techniques. Bubble formation was studied on the rotating disc electrode photographically. The experimental results support the following conclusions 1 Under most anodic and cathodic conditions in concentrated acids, the hydrogen electrode on Pt is under combined H2-diffusion and kinetic control. 2 Both the discharge and oxidation of H2 on Pt proceed through the combination mechanism with the atomic-combination step rate controlling. Two types of absorbed hydrogen appear to be involved--one strong at high coverage and one weak at lower coverage. Thus M- H e- M-HA MHA M-HB 2M-HB M- H2 where M-HA is the more strongly bound hydrogen. 3 In well purified solutions, extreme supersaturation with dissolved H2 occurs during cathodic polarization at high currents densities. 4 Theoretical considerations reveal that the transfer coefficient or its equivalent for the recombination and ion-plus-atom steps are probably closer to unity than the usual value of 12. Author
- Physical Chemistry