Effect of pH, Surfactant, and Temperature on Mixed-Phase Structure and Band Gap Properties of BiNbO4 Nanoparticles Prepared Using Different Routes

Abstract

α- and β-BiNbO4 nanoparticles were successfully prepared using three different routes, namely co-precipitation, hydrothermal, and citrate precursor methods. Structural characterization has been analyzed using powder X-ray diffraction where results confirmed the mixed-phase nature of the prepared powders. When co-precipitation method is applied, BiNbO4 prepared at pH 2 and calcined at 750 °C shows predominately the α-BiNbO4 owning the narrowest band gap of 2.86 eV, whereas an increase in the pH value resulted in the β-BiNbO4 phase being the predominant phase. On the other hand, samples prepared using citrate precursor method show co-existence of both α- and β-BiNbO4 at all pH values under study; however, at pH 10 the β-BiNbO4 was the dominant phase exhibiting a higher bandgap energy value of 3.16 eV. When applying the hydrothermal approach, BiNbO4 prepared at all pH ranges of the present study show a band gap >3.2 eV indicating their activity in the ultraviolet region of the spectrum. Moreover, increasing calcination temperature to 900 °C, a gradual transformation of α- to β was observed. Lastly, it was noticed that as the lattice volume increases, the band gap of prepared BiNbO4 decreases.

Efficient Visible-Light Photocatalytic Cycloaddition of CO2 and Propylene Oxide Using Reduced Graphene Oxide Supported BiNbO4

“…The average particle size was calculated using the Debye−Scherrer equation considering the broadening of the main peaks at half maximum 38 The PXRD patterns shown in Figure 1b are perfectly indexed to that of BiNbO 4 . 13 The broad peak observed at 2θ = 26.3°in Figure 1a corresponds to r-GO. The PXRD patterns of the BiNbO 4 /r-GO composite photocatalysts coincided with those of pure BiNbO 4 and r-GO in which all patterns indicate the presence of the two materials with no extra peaks corresponding to any impurities present.…”

“…The obtained yields are summarized in Table 4. The product was characterized using FT-IR, 1 H NMR, and 13 C NMR. FT-IR spectrum, 1 H NMR, and 13 Figure 8 illustrates the FT-IR of the cyclic propylene carbonate product.…”

“…The two solutions were mixed under constant stirring for 1 h using a Witeg MSH-20 D with the speed adjusted at 300 RPM. The reaction mixture was continued to be stirred for 24 h. The resulting as-synthesized white product was collected and calcined at 1023 K for 6 h. 13 Synthesis of BiNbO 4 /r-GO Nanocomposites. Three different photocatalysts composites, namely, BiNbO 4 /1% r-GO, BiNbO 4 /5% r-GO, and BiNbO 4 /10% r-GO, have been prepared using simple mechanical mixing followed by heat and high-pressure treatment in a hydrothermal reactor.…”

“…The N 2 adsorption−desorption isotherms were recorded at 77 K, showing the amount of gas adsorbed (cm 3 g −1 ) as a function of the relative pressure (p/p 0 ), where p is the equilibrium pressure of N 2 and p 0 is the saturated vapor pressure at 77 K. Prior to the BET measurements, the powder samples were placed in a glass tube and heated at 420 K under vacuum for 2 h. Fourier transform infrared (FT-IR) (IR Prestige-21, Shimadzu) was used to detect the product functionalities with frequency ranging from 500 to 3500 cm −1 . 1 H and 13 C NMR spectra were used to identify the structure of the obtained product using Varian 400 MHz in chloroform-d as a solvent. Photocatalytic Activity.…”

Physicochemical Properties of MoVTeNb Mixed Oxide Catalysts Synthesized using Different Vanadium Sources

“…X-RAY DIFFRACTION ANALYSIS Figure 1 shows the XRD patterns of all catalysts which demonstrate similar diffraction patterns comprises of four main crystalline phases which are orthorhombic (M1) phase at 2θ = 6.6, 7.9, 9.0, 22.1, 45.0° (JCPDS: 58-790), hexagonal (M2) phase at 2θ = 22.1, 28.1, 36.3, 45.0, 50 It should be noted that there is a peak shifting of MVTN-AMV at 2θ = 22.1 towards higher angle. This might be correlated to the increase in crystallite size of the catalyst as evidenced in Table 2 in which the crystallite size of MVTN-AMV is larger than MVTN-VO and MVTN-VS, due to the change in the phase composition of the catalyst (Bakiro et al 2019) caused by particle aggregation followed by crystal growth after washing treatment with H 2 O 2 . The development of other phase such as tetragonal phase was observed due to hydroxylation process which is the introduction of hydroxyl group into the catalyst.…”