Investigation on microstructural, morphological, optical properties of pristine 2D WO3 nanoplates synthesized by one-pot non-aqueous sol–gel solvothermal method for photocatalysis applications

Abstract

An original strategy based on a one-pot non-aqueous sol–gel solvothermal method was developed to synthesize 2D Tungsten trioxide (WO₃) nanoplatelets (identified as WO₃-180-24 NPs). The as-prepared catalyst was characterized by using various description technique such as XRD, SEM, TEM, FT-IR and UV–vis DRS. Additionally, comparative study of various microstructural parameters of chemically prepared WO₃-180-24 NPs based on the XRD peak broadening using different models (Scherrer (S, SEA and SS), Monshi-Scherrer (M-S), Williamson-Hall (W–H) (UD, USD and UDED), Size-Strain plot (SSP) and Halder-Wagner (H-W)). Therefore, WO₃-180-24 was efficiently investigated for sustainable removal of Rhodamine B (RhB) dye under LED-light illumination as a function of different removal processes. XRD results revealed the successful design of WO₃-180-24 NPs monoclinic sructure with space group P2₁/n (N°.14). By comparing microstructure parameters, Size-Strain Plot (SSP) and Halder-Wagner (H-W) models gave similar values of particle size D_XRD = 10.19 nm, negative lattice strain and the highest R² (0.870) means that WO₃-180-24 crystal has a compressivez strain. In comparison with Scherrer, W–H and H-W mthods, SSP model exhibited a minimum of microstrain (ε = 0.00101) which indicate the narrower size distribution, trivial strains and the presence of defects and size-shape anisotropy in the WO₃-180-24 environment. Further, the estimated higher value of strain (ε = 0.0162) for H-W method may be accredited to the lattice dislocations. WO₃-180-24 showed plate-like shaped particles which tend to form agglomerated plate-like nanostructures. WO₃-180-24 nanoplatelets are composed of quadrangular nanoplatelets with an average width of 35–50 nm. FT-IR study validated similar functional groups of WO₃. The band gap energy of 2.18 eV was obtained for the direc allowed electronic transitions of WO₃-180-24 NPs. The substantial red shift observed in band compared to that reported for the bulk WO₃ (~ 2.4–2.8 eV) could be assigned to the strong hybridization between W 5s and O 2p orbitals. Finally, the synthesized WO₃-180-24 NPs photocatalyst revealed substantially enhanced photocatalytic effectiveness of≈ 99% of RhB removed within 120 min, outperforming all other removal processes. Experimental kinetic study was correlated with the Langmuir–Hinshelwood kinetic model for pseudo first order reaction (R² > 0.98). The mechanistic understandings for the design of WO₃-180-24 NPs photocatalyst and its applications in the degradation of RhB dye was also covered in this investigation. Subsequently, the exceptional photocatalytic ability and versatile applications of WO₃-180-24 NPs-based photocatalyst, outperforming all other removal processes, could be can be synergysticaly educated by the combination of the photocatalysis oxidation process assisted by H₂O₂ and mediated by the RhB self-photosensitization mechanism through ROS (^•OH; O₂^•−, RhB^•+ and RhBO₂), as the robust oxidizing agents implicated in oxidation and reduction processes, W⁶⁺/W⁵⁺ redox system together with copious oxygen vacancies and large intrinsic crystal defects (W⁵⁺ -O defects sites), as primary driving forces ultimately facilitate charge separation of carriers, reduce their recombination rate and thus boost its photocayatlytic effectiveness.