UV-Vis Activated Cu2O/SnO2/WO3 Heterostructure for Photocatalytic Removal of Pesticides

Abstract

A three-steps sol–gel method was used to obtain a Cu2O/SnO2/WO3 heterostructure powder, deposited as film by spray pyrolysis. The porous morphology of the final heterostructure was constructed starting with fiber-like WO3 acting as substrate for SnO2 development. The SnO2/WO3 sample provide nucleation and grew sites for Cu2O formation. Diffraction evaluation indicated that all samples contained crystalline structures with crystallite size varying from 42.4 Å (Cu2O) to 81.8 Å (WO3). Elemental analysis confirmed that the samples were homogeneous in composition and had an oxygen excess due to the annealing treatments. Photocatalytic properties were tested in the presence of three pesticides—pirimicarb, S-metolachlor (S-MCh), and metalaxyl (MET)—chosen based on their resilience and toxicity. The photocatalytic activity of the Cu2O/SnO2/WO3 heterostructure was compared with WO3, SnO2, Cu2O, Cu2O/SnO2, Cu2O/WO3, and SnO2/WO3 samples. The results indicated that the three-component heterostructure had the highest photocatalytic efficiency toward all pesticides. The highest photocatalytic efficiency was obtained toward S-MCh (86%) using a Cu2O/SnO2/WO3 sample and the lowest correspond to MET (8.2%) removal using a Cu2O monocomponent sample. TOC analysis indicated that not all the removal efficiency could be attributed to mineralization, and by-product formation is possible. Cu2O/SnO2/WO3 is able to induce 81.3% mineralization of S-MCh, while Cu2O exhibited 5.7% mineralization of S-MCh. The three-run cyclic tests showed that Cu2O/SnO2/WO3, WO3, and SnO2/WO3 exhibited good photocatalytic stability without requiring additional procedures. The photocatalytic mechanism corresponds to a Z-scheme charge transfer based on a three-component structure, where Cu2O exhibits reduction potential responsible for O2 production and WO3 has oxidation potential responsible for HO· generation.

A heterostructured WO3–SnO2 nanocomposite for the efficient photocatalytic production of H2O2 under visible light

“…23,24 It is consequently seen that composite metal oxides compared of WO 3 and SnO 2 have attracted much attention due to their potentially excellent optical and electrical properties. 3,40,56 Actually, building heterojunctions of two or more semiconductors is one of the strategies to obtain novel photocatalysts, 22,25 and a number of studies have concentrated on the composite oxide systems containing WO 3 and SnO 2 , such as using WO 3 /SnO 2 /CuO for the photocatalytic degradation of methylene blue 26 and pesticides 27 and WO 3 /SnO 2 /TiO 2 for the degradation of polychlorinated biphenyl. 28 It should be noted that the aforementioned catalysts are mainly used in organic degradation processes, whereas the direct use of WO 3 -SnO 2 systems alone for the photocatalytic preparation of hydrogen peroxide is still rarely explored.…”