Simultaneous enhancement of natural sunlight- and artificial UV-driven photocatalytic activity of a mechanically activated ZnO/SnO₂ composite

Abstract

Mechanical milling of commercial ZnO and SnO2 was used to produce a ZnO/SnO2 composite with a high density of surface defects; in particular, zinc interstitials (Zni) and oxygen vacancies (VO).

Surfactant-assisted microwave processing of ZnO particles: a simple way for designing the surface-to-bulk defect ratio and improving photo(electro)catalytic properties

“…As expected, the average particle sizes measured in water suspensions were about threefold larger than those deduced from FE-SEM images, which is due to both the hydrodynamic diameter and particle sticking in dynamic uid conditions. 9 It is known that the presence of CTAB in different concentrations (from 0.1 to 0.8 M) can greatly change the shape of ZnO crystals obtained by hydrothermal or solvothermal synthesis. 44 In this study we established that even small amounts of surfactant, 0.0013 mol L À1 CTAB or 0.0029 mol L À1 Pluronic F127, affected the shape and size of microwave processed zinc oxide particles.…”

“…82 MB dye + reactive radicals / MB dye intermediates + reactive radicals / . / CO 2 + H 2 O + inorganic molecules (9) MB dye + h + (VB) / oxidation products (10) MB dye + e À (CB) / reduction products (11) The proposed photodegradation mechanism of MB dye on ZnO catalysts under direct sunlight irradiation is illustratively represented in Fig. 9(c).…”

“…7 In order to be suited for this purpose, photoactive materials need to: (1) absorb both ultraviolet and visible light irradiation producing electron-hole pairs, (2) separate electrons and holes in space to prevent their recombination, (3) provide rapid charge transfer across the electrode/electrolyte interface, (4) have suitable redox potentials to drive photo-oxidative reactions, (5) have a high photo-corrosion resistivity, and (6) to be recyclable, either for the sake of reuse or to prevent further water contamination. 3,[7][8][9][10][11][12] Over the years, metal oxides such as TiO 2 , ZnO, SnO 2 , Fe 2 O 3 , CoO, V 2 O 5 , WO 3 , etc., have been studied as the photoanodes for solar-driven PEC water splitting due to their high photoactivity and photostability. 4,8,[13][14][15][16][17][18][19] Noble metal nanocomposites, especially Ag-based, 20 as well as metal chalcogenides such as CuSe, CdS, MoS 2 , Ag 2 S, etc., have also been studied as promising visible light photocatalysts and electrocatalysts due to their suitable band gap (<2.5 eV) and excellent absorption of visible light.…”

“…Different approaches have been developed for enhancing the optical properties of ZnO materials: incorporation of transition metal ions into the crystal structure, sensitization of particle surface, hydrogenation, incorporation of crystalline defects in metal oxide semiconductors in the form of vacancies and interstitials, etc. 9,[27][28][29][30] Crystalline defects can strongly inuence electrical and optical properties of a semiconductor. Defects oen introduce levels in the band gap of semiconductors; 31 these levels involve transitions between different charge states of the same defect.…”

A ZnO@ABS/TPU/CaSiO3 3D skeleton and its adsorption/photocatalysis properties for dye contaminant removal

“…Compared with ltration or sedimentation, photocatalysis [1][2][3] directly decomposes pollutants into environmentally sound substances, which means it does not require complex post-treatment procedures, thus greatly reducing the operating cost in practical applications. Currently, semiconductor metal oxides are still the main photocatalysts in many processes, among which zinc oxide (ZnO, 3.37 eV) [4][5][6] has been widely used to degrade organic pollutants in wastewater due to its high photosensitivity, high stability, relatively low toxicity, and low synthesis temperature. 7,8 In addition, adjusting the precursor and reaction time is a simple way to control the structure size and morphology of ZnO, as is increasing the specic surface area and crystallinity, and synthesizing nanoparticles or a hierarchical assembly of nanoscale structures (the most effective form of metal oxides), which can provide a wide photo-response range because the electron-hole pairs improve the separation efficiency.…”