Rapid reduction of nitroarenes photocatalyzed by an innovative Mn(3)O(4)/α-Ag(2)WO(4) nanoparticles

A novel photocatalyst based on the design of P-N heterojunction between hollow spherical Mn(3)O(4) and nanorods shape of α-Ag(2)WO(4) is synthesized using a sonication-deposition–precipitation route. The nanocomposite Mn(3)O(4)/α-Ag(2)WO(4)(60%) exhibits a great potential towards nitroarenes (including 4-nitrophenol, 4-nitro-aniline and 4-Nitro-acetanilide) reduction under visible light irradiation exceeding that of Mn(3)O(4)/α-Ag(2)WO(4)(40%) as well as their individual counterparts (3–5%). The Mn(3)O(4)/α-Ag(2)WO(4)(60%) catalyst exhibited an excellent photo-reduction activity comprised of 0.067 s(−1) towards 4-nitrophenol (0.001 M) in only 60 s reaction time using NaBH(4) (0.2 M). This was due to the successful formation of the Mn(3)O(4)/α-Ag(2)WO(4) composite as validated by XRD, TEM-SAED, XPS, FTIR, UV–Vis diffuse reflectance and PL techniques. Decreasing the E(g) value into 2.7 eV, the existence of a new (151) plane in the composite beside enhancement of the composite electrical conductivity (1.66 × 10(–7) Ω(−1) cm(−1)) helps the facile nitroarenes adsorption and hydrogenation. Transient photocurrent response and linear sweep voltammetry results prove the facilitation of photogenerated charge carriers separation and transport via improving electron lifetime and lessening recombination rate. The composite photocatalyst produced higher amounts of H(2) production, when inserted in a typical reaction medium containing NaBH(4), comprised of 470 µ mole/g exceeding those of the counterparts (35 µ mole/g). This photocatalyst is strikingly hydrogenated 4-nitrophenol under mild conditions (25 °C and 0.35 MPa pressure of H(2)) with magnificent rate constant equal 34.9 × 10(−3) min(−1) with 100% selectivity towards 4-aminophenol.