HYDROGEN IN SOME SYNERGETIC ELECTROCATALYSTS

The interaction of hydrogen with electrodeposits of some electrocataly tic alloys with synergetic effects has been studied by thermal desorpt ion spectroscopy and the potential sweep method. The alloys can be ele ctrochemically charged with hydrogen more easily than from the gas pha se, the H content decreasing in the series Co-Mo>Co-W>Ni-Mo. The highe st value observed is for Co-Mo (0.182 w/o H). showing two types of H w ith different bond strength. The overall activation energy obtained fr om thermal desorption of hydrogen agrees well with that calculated fro m thr temperature dependence of the anodic peak. This shows that the H diffusion in the bulk or on the surface is the rate controlling step in both processes. It is inferred that, in the range -20 to 10 degrees C, the anodic oxidation of H in KOH solution is the main process for the discharge of hydrogenated Co-Mo (62.6 w/o Co) electrodes, while Co -->Co(OH)(2)+2e(-) is significant only at higher temperatures. The mec hanism of H diffusion in these synergetic electrocatalysts seems to be related to the mixed valence states of Mo(W).