Highly photocatalytic activity of metallic hydroxide/titanium dioxide nanoparticles prepared via a modified wet precipitation process

Surface modification is one important approach to increase the photocatalytic activity of TiO2. By using a modified wet precipitation process, novel M(OH)x/TiO2 nanoparticles were synthesized, where M(OH)x represents ferric or cupric hydroxide. The prepared M(OH)x/TiO2 powders were characterized with XRD, FT-IR, BET, UV–vis DRS, and TGA, and were observed to yield high photocatalytic ability by using methyl orange (MO) as a model compound of organic pollutants to be degraded. Due to the accelerating effects of the new photocatalyst, the half-time of MO during its photocatalytic degradation at pH 6.0 over M(OH)x/TiO2 was decreased from 332 min for unmodified neat TiO2 to 63 min for Fe(OH)3/TiO2 and 65 min for Cu(OH)2/TiO2, respectively. The enhancing effects of M(OH)x/TiO2 was further observed in a wide composition range with various M/Ti atomic ratios in the photocatalysts and in a wide pH range of the MO solution from 3 to 7. This enhancing effect is mainly attributed to the increased trapping of the photogenerated electron by the higher valence sites (Fe(III) or Cu(II)) in the hydroxide layer near the M(OH)x/TiO2 interface and the enriched surface hydroxyl groups which accept photogenerated holes to yield more hydroxyl radicals.