Electrochemical behavior of gold, palladium and platinum as inert anode materials for molten chloride electrolysis

International audienceElectrochemical behavior of gold, palladium and platinum as anode materials was studied in a molten chloride media CaCl2 – CaO (0–2 wt%) at 850 °C in order to determine the feasibility of their use as oxygen evolving anodes for electro-deoxidation processes such as the Fray-Farthing-Chen (FFC) Cambridge and Ono and Suzuki (OS) processes. Linear sweep voltammetry measurements and constant current electrolyses were conducted in line with oxygen analysis and mass variation measurements to identify anodic reactions that can occur. It was found that oxygen evolution is possible on gold anode but the metal also undergoes a degradation due to gold chloride AuClx formation. Palladium has to form an oxide layer on its surface to evolve oxygen but is also damaged by PdClx formation. Platinum is the most interesting metal as O2 gas can be produced without damaging the material with a good control of electrolysis conditions such as current density and CaO concentration