Ruthenium sulphide thin layers as catalysts for the electrooxidation of water

Abstract

Crystalline RuS₂ layers were prepared on titanium sheets by reactive magnetron sputtering using a metallic ruthenium target and a H₂S–Ar mixture as process gas. The ability of these layers for the electrooxidation of water (OER) was investigated by differential electrochemical mass spectrometry (DEMS) in 0.5 M H₂SO₄ electrolyte. It was observed that the activity for water oxidation is increased with increasing temperature of the titanium substrate during the sputter deposition process whereas a competitive corrosion process is diminished. The reason for this effect seems to be a better crystallinity of these layers at higher substrate temperatures as it is proved by XRD analysis. In contrast to RuS₂ single crystals no photo effect could be observed on the sputtered layers under illumination with a tungsten lamp. Time resolved microwave conductivity analysis indicates the presence of mobile charge carriers after illumination but apparently these cannot participate in the electrooxidation of water.