BARRIERLESS DISCHARGE OF HYDROXONIUM IONS ON MERCURY AT TEMPERATURES OVER 100-DEGREES-C IN LIGHT AND HEAVY-WATER

The cathodic hydrogen evolution on mercury from acid aqueous solutions without specifically adsorbable ions has been studied. It is shown that at temperatures above 120-degrees-C and overvoltages about 400 mV and lower, the kinetics possess all the characteristic features of a barrierless process. The kinetics of hydrogen evolution from solutions in H2O and D2O are compared. Analysis of the obtained data, their comparison with the isotope effect observed during electrolysis of a mixture of isotopes (hydrogen-tritium) has shown that (1) a significant role in the slow discharge of hyroxonium ions is played by the work of approach of reagents to the electrode; (2) this work is determined, at least partly, by the forces keeping the proton donor in the solution; (3) the electrode field exerts an influence on these forces and (4) this influence depends on the properties of the medium.