Chromium Oxide-Ruthenium Oxide Solid Solution Anode Implemented in a Solid Phosphate Electrolyzer at 240 °C and 28 Bar Overpressure

Abstract

This work offers an overview of the synthesis and implementation of various chromium-ruthenium oxide materials for gas-phase solid-acid water electrolysis under hydrothermal conditions (240 °C, 28 bar of Ar and steam overpressure). The oxidic solid solutions show general stability over a broad chromium concentration range in the RuO2 rutile structure during synthesis. Decomposition of the solid solutions is observed over a potential of around 2.1 V during electrolysis (including the Ohmic contribution of the setup and cell). Electrolysis performed below this decomposition potential shows promising results for replacing pure RuO2 with a low ruthenium-containing anode. Special attention has been given to Cr0.6Ru0.4O2 for being less expensive because of the lower ruthenium content and showing good stability and comparable performance to RuO2 during continuous chronopotentiometry operation for 1 h at 75 mA cm−2 current densities.