Efficient Ozone Evolution Anode of Tantalum Nitride with Cubic Crystal Structure

Abstract

Highly selective, nontoxic, and low-cost electrodes for the electrochemical ozone evolution reaction (OZER) have been explored for widespread use in water electrolysis ozone production devices. Herein, the OZER properties of tantalum nitride (TaN) thin-film anodes with cubic, hexagonal, and mixed crystal structures are discussed. The cubic-TaN thin film outperformed the ozone evolution property of conventional PbO 2 -and SnO 2 -based electrodes in 0.5 M H 2 SO 4 at room temperature, with a faradaic efficiency of approximately 37.5% at 4.7 V. In contrast, the TaN thinfilm anode with a hexagonal structure mostly generated oxygen in the tested potential region: both cubic and hexagonal mixed structures of TaN revealed intermediate ozone evolution efficiency. After the ozone evolution by chronopotentiometry, amorphous tetravalent and pentavalent surface TaO x layers were generated depending on the crystal structures of the TaN anode surfaces. These results suggest that the number of oxidation defects in the surface TaO x layers generated by anodic polarization determines the ozone evolution efficiencies of TaN thin-film anodes.