Zirconium Oxycarbide: A Highly Stable Catalyst Material for Electrochemical Energy Conversion

Metal carbides and oxycarbides have recently gained considerable interest due to their (electro)catalytic properties that differ from those of transition metals and that have potential to outperform them as well. The stability of zirconium oxycarbide nanopowders (ZrO_0.31 C_0.69 ), synthesized via a hybrid solid-liquid route, is investigated in different gas atmospheres from room temperature to 800 °C by using in-situ X-ray diffraction and in-situ electrical impedance spectroscopy. To feature the properties of a structurally stable Zr oxycarbide with high oxygen content, a stoichiometry of ZrO_0.31 C_0.69 has been selected. ZrO_0.31 C_0.69 is stable in reducing gases with only minor amounts of tetragonal ZrO₂ being formed at high temperatures, whereas it decomposes in CO₂ and O₂ gas atmosphere. From online differential electrochemical mass spectrometry measurements, the hydrogen evolution reaction (HER) onset potential is determined at -0.4 V_RHE . CO₂ formation is detected at potentials as positive as 1.9 V_RHE as ZrO_0.31 C_0.69 decomposition product, and oxygen is anodically formed at 2.5 V_RHE , which shows the high electrochemical stability of this material in acidic electrolyte. This peopwery makes the material suited for electrocatalytic reactions at anodic potentials, such as CO and alcohol oxidation reactions, in general.