LUO Ze-min, LI Yan, LU An-huai, WU Jing, QIN Shan, WANG Changqiu
（Key Laboratory of Orogenic Belts and Crustal Evolution of MOE, School of Earth and Space Science, Peking University, Beijing 100871, China）
Abstract: Natural semiconductor mineral rutile-TiO2, containing the main substituting metal ions of vanadium and iron, has potential capability on optical absorption and photocatalytic activity under sunlight. To further enhance its optical absorption, the rutile powder was modified by using hydrogen heat treatment in the temperatures ranging from 500℃to 900 ℃. The Ultra violet-visible (UV-Vis) absorption spectra showed that the visible light absorption of rutile sample in the wavelength from 460 to 750 nm was significantly enhanced, with the biggest increment in sample treated at 900℃. Analysis with Electronic Paramagnetic Resonance (EPR) and X-ray Photoelectron Spectroscopy (XPS) indicated that hydrogen heat treatments induced transformation from V5+ to V4+ and V3+, as well as from Fe3+ to Fe2+ in rutile samples, and the atom percentages of chemical absorbed water was gradually increased with increasing temperature. Changes of transition metals, especially the formation of V4+ and V3+, were regarded as the main reason for the substantial improved optical absorption in this work.
Key words: natural rutile; hydrogen heat treatment; visible light absorption; EPR
