The Photocatalytic Activities Induced by Sulfurization-Oxidation Processing of SrHfO₃

Abstract

Since hafnium belongs to the same group of elements as titanium and zirconium, SrHfO₃ may have photocatalytic activity comparable to those observed for SrTiO₃ and SrZrO₃. The band gap of SrHfO₃ is too large to be excited in the visible region of light. To improve this sulfurization-oxidation cyclic processings were tried. The sulfurization was made in CS2atmosphere (13.3 Pa) at 900°C, and then oxidation was made in O₂ atmosphere (0.1 MPa)at 600°C. The SrHfO₃ treated by three cyclic processings became to absorb visible light. The SrHfO₃ catalyst, thus prepared photolyzed H₂O-2-propanol and H₂O-methanol system with quantum efficiencies as high as 9.7%. Such visible light responsiveness may have been caused by the introduction of SO₂- ions during the CS₂-O₂ processing cycle.