Tailored mesoporous γ-WO3 nanoplates: unraveling their potential for highly sensitive NH3 detection and efficient photocatalysis

Abstract

Herein, the monoclinic phase of tungsten oxide (γ-WO₃) was successfully obtained after annealing hydrothermally synthesised WO₃ powder at 500 °C. As per the result obtained from the N₂ adsorption–desorption isotherm, the material has been identified as mesoporous with a specific surface area of 3.71 m² g⁻¹ from BET (Brunauer–Emmett–Teller) analysis. Moreover, the average pore size (49.52 nm) and volume (0.050 cm³ g⁻¹) were also determined by the BJH (Barrett–Joyner–Halenda) method. FE-SEM (field emission scanning electron microscopy) and HR-TEM (high resolution transmission electron microscopy) have confirmed the formation of nanoplates with an average diameter of approximately 274 nm. Raman spectroscopy has shown peaks at the lower wavenumber region (270 cm⁻¹ and 326 cm⁻¹) and the higher wavenumber region (713 cm⁻¹ and 806 cm⁻¹) for O–W–O bending modes and stretching modes, respectively. The combined effect of relative humidity (RH-11%–RH-95%–RH-11%) and NH₃ (150 ppm, 300 ppm, 450 ppm, 600 ppm, 700 ppm, and 800 ppm) was investigated in this reported work. The synthesised γ-WO₃ has shown highly responsive behaviour for humidity of 96.5% (RH-11%–95%) and NH₃ sensing (under humidity) of 97.4% (RH-11%–95% with 800 ppm NH₃). The response and recovery time were calculated as 15 s and 52 s, and 16 s and 54 s for humidity, and NH₃ under humidity, respectively. The experimental findings demonstrated that the resistance of the sensor depends on the concentration of NH₃ and humidity. Moreover, γ-WO₃ has been investigated as a promising catalyst for the dye degradation of methylene blue (MB) with a degradation efficiency of 72.82% and methyl orange (MO) with a degradation efficiency of 53.84% under visible light exposure. This dye degradation occurred within 160 min in the presence of a catalyst under visible light irradiation.