ELECTROCHEMICAL-BEHAVIOR OF GOLD IN ACIDIC AND ALKALINE-SOLUTIONS OF HEAVY AND REGULAR WATER

The behaviour of gold as an electrode for hydrogen (protium and deuterium) and oxygen evolution in both alkaline and acidic, heavy and regular water solutions has been investigated primarily by cyclic voltammetry. All the main features, such as adsorption accompanied by absorption of hydrogen (both protium and deuterium), as well as the specific multilayer (monolayer alpha- succeeded by multilayer beta-phase) oxide growth preceding hydrogen and oxygen evolution, respectively. with characteristic desorption peaks within a wider potential range distinctive (and typical) for gold, were clearly marked in both electrolytes. Some distinctly different features, however, have been observed, revealing that heavy and regular water behave almost as different solvent ambients. In particular, twin peaks for oxygen desorption, which progressively separate along the potential axis with cyclization, were clearly marked in heavy water solutions. The hydrogen evolution reaction (HER) in heavy water occurs at substantially more negative potentials. while oxygen evolution becomes shifted to considerably more positive potential values. The latter effect enables one to record on voltammograms the multilayer oxide (beta-phase) growth in alkaline heavy water. as distinctly indicated by the corresponding, continuously growing, characteristic potentiodynamic waves scanned successively with cyclization. Deuterium absorption has been clearly marked by the continuously growing charge capacity of the diffusional desorption peak, which exceeds one-to-one D(H)/Au atom coverage on the exposed gold surface, relative to the corresponding steady-state adsorption wave for hydrogen deposition preceding its evolution. In addition, the hydrogen oxidation peak immediately following its desorption (in particular from acidic heavy water) has also been distinctly scanned on voltammograms. Oxide formation usually starts together with deuterium oxidation and, specifically in acidic media, proceeds vigorously with higher and continuously growing rates, while evolving oxygen thereby becomes shifted to more positive potential values. These features reveal that due to its distinctly different steric factor, heavy water, in particular in acidic media, behaves as a stronger oxidizing agent than regular water. Some discernible properties of the interplay between hydrogen and oxygen on gold electrodes in both electrolytes along the potential axis have been clearly marked and pointed out.