PHOTOELECTROCHEMICAL PROPERTIES OF RUS2-COATED TIO2 ELECTRODES

Photoelectrochemical studies of RuS2-coated TiO2 electrodes showed sem iconductor sensitization by RuS2 fine particles on TiO2. RuS2 particle s of ca. 100 nm size were observed from a scanning electron micrograph of the RuS2/TiO2 electrode surface. RuS2-coated TiO2 electrodes showe d continuous wide absorption in the visible spectral region. Photoelec trochemical measurements of several RuS2/TiO2 electrodes, prepared und er different conditions, were carried out. The electron-transfer effic iency from RuS2 to TiO2 was affected by the number of RuS2 colloid coa tings and the preparation temperature of the RuS2 colloids. A schemati c study was carried out on the effect of a, heat treatment in order to find the optimum temperature for the maximum sensitization efficiency . A comparison of the absorption and action spectra of the RuS2/TiO2 e lectrode showed that only small RuS2 particles with a critical size di stribution could transfer the photo-generated electrons to TiO2. A ban d-gap value of ca. 2.8 eV was evaluated (from the photocurrent action spectrum) for the RuS2 particles with high sensitization efficiency. A scheme which shows the energy diagram for RuS2 fine particles has bee n proposed by considering the hat-band potential values derived from t he photocurrent onset potentials and the above-mentioned band-gap valu e.