Photocatalytic Activity of ZnWO₄: Band Structure, Morphology and Surface Modification

Abstract

Photocatalytic degradation of organic contaminants is an important application area in solar energy utilization. To improve material photocatalytic properties, understanding their photocatalytic mechanism is indispensable. Here, the photocatalytic performance of ZnWO4 nanocrystals was systematicly investigated by the photodegradation of tetraethylated rhodamine (RhB) under simulated sunlight irradiation, including the influence of morphology, AgO/ZnWO4 heterojunction and comparison with CoWO4 nanowires. The results show that the photocatalytic activity of ZnWO4 is higher than that of CoWO4, and the ZnWO4 nanorods exhibit better photocatalytic activity than that of ZnWO4 nanowires. In addition, the mechanism for the difference of the photocatalytic activity was also investigated by comparison of their photoluminescence and photocurrents. AgO nanoparticles were assembled uniformly on the surface of ZnWO4 nanowires to form a heterojunction that exhibited enhanced photocatalytic activity under irradiation at the initial stage. We found that a good photocatalyst should not only have an active structure for electrons directly to transfer from the valence band to the conduction band without the help of phonons but also a special electronic configuration for the high mobility, to ensure more excited electrons and holes in a catalytic reaction.

Tuning of the crystal engineering and photoelectrochemical properties of crystalline tungsten oxide for optoelectronic device applications

“…19 Many crystalline hydrated tungsten trioxide compounds with the general formula WO 3 ⋅nH 2 O with n = 1/3 (0.33), 0.5, 0.75, 1, 2, etc., have been reported. 32 Their crystal phases are orthorhombic WO 3 ⋅0.33H 2 O, 33 45 Bi 2 WO 6 , 46 PbWO 4 , 47 and CdWO 4 , 48 have been studied for different applications. For example, CuWO 4 has been studied for PEC water splitting 6b,44 and Bi 2 WO 6 for CO 2 reduction.…”

Time‐ and Energy‐Efficient Solution Combustion Synthesis of Binary Metal Tungstate Nanoparticles with Enhanced Photocatalytic Activity

“…There are many examples where the photocatalytic or photoelectrochemicalp erformance of binary (or even ternary) tungstates outperformed WO 3 , [6] notably, Bi 2 WO 6 , [7][8][9] SnWO 4 , [10,11] ZnWO 4 , [12][13][14] AgBiW 2 O 8 , [15] and AgInW 2 O 8 . There are many examples where the photocatalytic or photoelectrochemicalp erformance of binary (or even ternary) tungstates outperformed WO 3 , [6] notably, Bi 2 WO 6 , [7][8][9] SnWO 4 , [10,11] ZnWO 4 , [12][13][14] AgBiW 2 O 8 , [15] and AgInW 2 O 8 .…”

Eu2+ and Eu3+ Doubly Doped ZnWO4 Nanoplates with Superior Photocatalytic Performance for Dye Degradation

“…The open circles in Figure 2a represent the experimental data. As shown in Figure 2a, diffraction peaks at 14.98°, 18.86°, 23.56°, 24.36°, 38.30° and 48.36° can be assigned to the reflections from the (010), (100), (011), (110), (200), and (022) planes of monoclinic ZnWO 4 [3,27], respectively, whereas the peak at 30.40° is ascribed to the combined contributions from (111), ($\overline{1}11$),and (020) crystallographic planes as these diffractions are located too closely [2,3,6,7,10,16]. For the same reason, the four peaks located at 36.20°, 40.94°, 44.22° and 45.76° can be ascribed to the contributions from the pairs of planes (021) and (002), (121) and ($\overline{1}21$), (112) and ($\overline{1}12$), and (211) and ($\overline{2}11$), respectively.…”

“…Belonging to a wide group of wolframite-type tungstates, zinc tungstate (ZnWO 4 ) is a technologically important material for numerous applications in the fields of luminescent materials [1,2,3,4,5], photocatalysts [6,7,8,9,10,11,12,13,14], Li-ion batteries [15], humidity sensors [16], materials for stimulated Raman scattering [17], and materials for deactivating microorganisms [18]. Among these applications, the photocatalytic properties of ZnWO 4 nanostructures have been intensively investigated in order to solve one of the most serious environmental problems in our modern society via semiconductor-based photocatalytic degradation of organic contaminants in water under sunlight [6,7,8,9,10,11].…”

“…Among these applications, the photocatalytic properties of ZnWO 4 nanostructures have been intensively investigated in order to solve one of the most serious environmental problems in our modern society via semiconductor-based photocatalytic degradation of organic contaminants in water under sunlight [6,7,8,9,10,11]. Up to date, a diverse range of strategies has been developed to enhance the photocatalytic activity of ZnWO 4 nanostructures, which can be classified into three categories: (i) synthesis of ZnWO 4 nanorods and nanosheets with large specific surface area [19]; (ii) coupling ZnWO 4 with other semiconductors and metals such as In 2 S 3 [20], Ag [21], ZnO [22], and Cu 2 O [23]; and (iii) defect engineering ZnWO 4 via doping with non-metal ions (B, C, N, F) [24,25,26], transition metal ions (Sn 2+ , Cr 3+ , Mn 2+ , Cu 2+ ) [27,28], and lanthanide ions (Dy 3+ , Er 3+ ) [29,30].…”