Controlled preparation of M(Ag, Au)/TiO₂ through sulfydryl-assisted method for enhanced photocatalysis

Here a simple and effective method was explored to fabricate M/TiO₂ (M = Ag, Au) composites, which required neither pre-treatment of TiO₂ nor any additives as reducing agent. Using amorphous TiO₂ spheres functionalized with SH groups as starting materials, the noble metallic ions (Ag, Au) can be adsorbed by TiO₂ due to their special affinity with SH groups, which is beneficial to the uniform dispersion of metallic ions on the surface of TiO₂. Then the adsorbed ions were reduced to form noble metal nanoparticles by heating process (95 °C) directly without additive as reduction agent. Meanwhile, the amorphous TiO₂ was transformed into anatase phase during the heating process. Thus, the transformation of TiO₂ along with the reduction of noble metallic ions (Ag, Au) was simultaneously carried out by heating. The XRD patterns proved the formation of anatase TiO₂ after heating. The characterizations of XPS and TEM proved the formation of Ag and Au nanoparticles on the surface of TiO₂. The element mapping indicated that Ag nanoparticles are dispersed uniformly on the surface of TiO₂. The photocatalytic activity of the composites has been investigated by the degradation of methyl orange under visible light irradiation. The results showed that when Ag/TiO₂ (2.8 wt%) was used as photocatalyst, about 98% of the MO molecules were degraded in 70 min.