Photocatalytic primary alcohol oxidation on WO3 nanoplatelets

Abstract

With the aid of direct heating through microwave irradiation in non-aqueous media, nanocrystalline tungsten(vi) oxide is achievable in 30 minutes at 200 °C, faster and at a lower temperature than conventional synthesis methods. Forming in a platelet morphology, these particles are as small as 20 nm with a BET surface area of 37 m2 g-1 WO3. These nanoplatelets are active for the photocatalytic oxidation of the 1° alcohols benzyl alcohol (rate constant, k of 2.6 × 10-3 h-1) and 5-(hydroxymethyl)-2-furfural (k of 0.01 h-1) using 10 mg of WO3 with 2 mL of 0.250 M substrate in acetonitrile and a 150 mW cm-2 460 nm blue LED source. As expected, these rate constants are larger than those observed for commercially prepared, micron-sized WO3. XPS analysis shows that during catalysis, the concentration of W5+ on the surface increases, but the nanoplatelets are stable under these reaction conditions. The overall morphology and size of the particles are retained through the reactions. Moreover, the nanoplatelets are recyclable - showing no loss in activity for four reaction cycles.