Rhenium reactivity in H2O-O2 supercritical mixtures at high pressures

Rhenium (Re) gaskets are commonly used in diamond anvil cell experiments to contain and pressurize samples. It is found that Re undergoes a series of reactions with supercritical fluid H2O-O2 mixtures at room temperature to form perrhenic acid (HReO4) and its hydrates. Similar reactivity of Re is also observed by destabilization of oxygen clathrate hydrates. The reaction mechanism is consistent with the electrochemistry of metal corrosion in an aqueous media. From a practical perspective for high pressure research, this finding indicates the need to consider the reactivity of Re when it is used as a gasket in experiments on aqueous fluids. More importantly, the documentation of these reactions demonstrates the oxidative potential of H2O-O2 supercritical mixtures for beneficial practical implications.