New strategy for the in situ synthesis of single-crystalline MnWO₄/TiO₂photocatalysts for efficient and cyclic photodegradation of organic pollutants

Abstract

MnWO 4 nano photocatalysts with plate shapes and in high yields are in situ synthesized on the surface of a porous TiO 2 film by the conventional plasma electrolytic oxidation (PEO) method combined with a subsequent ambient annealing process. Transmission electron microscopy (TEM) analysis shows that the MnWO 4 nano photocatalysts are single crystals free of structural defects and scanning electron microscopy (SEM) observation on the cross-section reveals that these MnWO 4 nano photocatalysts are in situ grown on the porous TiO 2 film surface with strong adhesion. The morphology and dimension size can be selectively tailored through controlling the reaction time, showing the simplicity and versatility of the proposed method.In addition, the photodegradation of methylene blue (MB) solution using the MnWO 4 /TiO 2 photocatalysts demonstrated the superior photocatalytic performance with high efficiency and excellent photostability. A high photodegradation rate of MB solution of over 90% in 60 min has been achieved and a superior cyclic capability is also obtained. The superior photocatalytic performance of MnWO 4 /TiO 2 photocatalysts can be mainly attributed to the good crystallinity, all-surface covering and strong mechanical properties of the MnWO 4 nanostructures with TiO 2 film. The prevailing advantage of the PEO method in combination with the ambient annealing process will open up more opportunity for the rational synthesis of a wide range of oxide photocatalysts ranging from tungstate to titanate, molybdate and vanadate for promising catalytic applications in diverse fields.

Nanostructured Ternary Metal Tungstate-Based Photocatalysts for Environmental Purification and Solar Water Splitting: A Review

“…As discusses in the previous section, the MWO 4 with a small M 2+ cation has a narrow band-gap energy, which can be considered an efficient solar energy harvester to connect with wide band-gap semiconductors for constructing MWO 4 -based heterojunctions [ 159 – 161 ]. Thus, Jiang et al [ 162 ] fabricated an MnWO 4 /TiO 2 heterojunction with excellent mechanical adhesion by the in situ growth of MnWO 4 on a porous TiO 2 film; it presented extremely high photocatalytic performance for degrading MB because of its high crystallinity, large surface area, and strong mechanical properties (Fig. 15 ).…”

Selective synthesis of scheelite/perovskite CdWO4 nanoparticles: a mechanistic investigation of phase formation and property correlation

“…), have been studied extensively owing to their intriguing physical and chemical properties. Particularly AMO 4 type oxides (A = Zn, Cd, Pb, and Cs, M = W and Mo), draw the attention of researchers for their wide range of applications in photoluminescence [1], scintillators [2], photochromism [3], multiferroic materials [4], and photocatalysis [5][6][7]. The divalent metal tungstates and molybdates with small A 2+ ion (radius ≤0.77 Å: Mg, Mn, Fe, Co, Ni, Cu, and Zn) crystallizes in wolframite type structures and with large A 2+ ion (radius ≥0.99 Å: Ca, Sr, Ba, and Pb) crystallizes in scheelite type structures.…”

Flexible Co3O4/TiO2 monolithic catalysts for low‐temperature and long‐term stable CO oxidation

“…I n‐situ Growth of TiO 2 Nanostructures on Ti Mesh : Conventional PEO technology was utilized to prepare porous TiO 2 seed layer on the surface of Ti mesh substrate, as reported in our previous works. [ 31,32,44–48 ] The surface oxidation of Ti mesh was carried out in 10 g L −1 Na 3 PO 4 aqueous solution for about 5 minutes at 0.015 A cm ‐2 current density. The duty cycle, frequency and cut‐off voltage of plasma discharge were maintained at 60%, 1000 Hz and 380 V, respectively.…”