Nanoscale β-Sn1−nWO4·nα-Sn—A highly efficient photocatalyst for daylight-driven degradation of organic dyes and its real “green” synthesis

Abstract

The unique phase composition β-Sn1−nWO4·nα-Sn, including nanoscale incipient crystalline β-SnWO4 and α-Sn, turned out to be a very promising photocatalyst under simulated daylight. Since the nanomaterial is gained via a quick and simple precipitation in water without using toxic elements or solvents, the synthesis can be regarded as real “green”. Despite its simple preparation, the nanoparticles are of high quality, exhibiting an average diameter of 20nm, a low degree of agglomeration, a high specific surface (71m2g−1) and an efficient electrostatic stabilization (ζ<−40mV at pH=3.5–9.5). As-prepared β-Sn1−nWO4·nα-Sn exhibits a strong absorption in the visible spectral range (554nm, 2.2eV) and a lasting high photocatalytic performance under simulated daylight. Various organic dyes (phenothiazine dye methylene blue, triphenylmethane dye basic green 4, azo-dye methyl red) are decomposed with significantly higher degradation rates (5–10) as compared to commercially available Degussa P25 (TiO2, 80% anatase, 20% rutile). Recycling experiments prove the phase stability and reusability of as-prepared β-Sn1−nWO4·nα-Sn.