Mesoporous WS₂/MoO₃ Hybrids for High-Performance Trace Ammonia Detection

Abstract

Mesoporous WS 2 /MoO 3 hybrids were synthesized by a facile two-step and additive-free hydrothermal approach and employed for high-performance trace ammonia gas (NH 3 ) detection. Compared with single WS 2 and MoO 3 counterparts, WS 2 /MoO 3 sensors exhibited an improvement in NH 3 -sensing performance at room temperature (22 ± 3 °C). Typically, the optimal WS 2 /MoO 3 sensor showed a higher and quicker response of 31.58% within 57 s toward 3 ppm of NH 3 , which was 17.7-and 57.4-fold larger than that of pure MoO 3 (1.78% within 251 s) and WS 2 (0.55% within 153 s) ones. Meanwhile, good reversibility, sensitivity, and selectivity, reliable long-term stability, and the lowest detection limit of 9.0 ppb were achieved. These superior properties were probably ascribed to numerous heterojunctions favorable for additional carrier-concentration modulation via the synergetic effect between WS 2 and MoO 3 components and the large specific surface area beneficial for richer sorption sites and faster molecular transfer at room temperature. Such achievements also imply that the designed WS 2 /MoO 3 heterostructure nanomaterials have the potential in achieving trace NH 3 recognition catering for the requirements of high sensitivity and low power consumption in future gas sensors.

Mo2C/MoO3@rGO Ternary Nanocomposites as High-Performance Gas Sensor for Trace NH3 Detection at Room Temperature

“…The ternary composite gas sensors exhibit a better gas response at 40% RH compared to 20% RH probably due to the moderate amount of water molecules involved in the gas-sensitive response process, acting as a cocatalyst . In contrast, at higher relative humidity, the excess water molecules occupied the gas adsorption sites on the material surface and hindered the absorption of NH 3 molecules, resulting in a poor response . Although the gas-sensitive response of Mo–O–C@rGO-3 decreased with the relative humidity, its response value still remained at a high level, even at 80% relative humidity with a response of 0.748.…”

“…At room temperature, the absorbed oxygen ion on the surface of the material is mainly O 2 – . A process shown in eqs and demonstrates the gas response process when the sensor is exposed to the reducing gas NH 3 . , NH 3 can react with the chemisorbed oxygen ions on the MoO 3 surface to produce N 2 and H 2 O, while releasing the captured electrons back into MoO 3 , resulting in a narrowing of the electron depletion layer and a reduction in material resistance . However, due to the large size of the MoO 3 grains and the small percentage of the depletion layer, the effect of trace gas charge on the depletion layer width is not obvious, which limits the ability of pure MoO 3 to detect NH 3 at low concentrations.…”

“…18 In contrast, at higher relative humidity, the excess water molecules occupied the gas adsorption sites on the material surface and hindered the absorption of NH 3 molecules, resulting in a poor response. 17 Although the gas-sensitive response of Mo−O−C@rGO-3 decreased with the relative humidity, its response value still remained at a high level, even at 80% relative humidity with a response of 0.748.…”

“…Several promising metal oxides have been investigated for NH 3 detection, including WO 3 , SnO 2 , ITO, TiO 2 , ZnO, V 2 O 5 , CuO, and MoO 3 . , Molybdenum trioxide (MoO 3 ), an important n-type semiconductor with a wide bandgap, has been widely applied in battery electrodes and photocatalysis . Due to its thermodynamic stability and high reactivity to certain reducing agents, MoO 3 has received attention in gas detection and has been studied for the detection of TMA, ethanol, H 2 S, NO 2 , NH 3 , – etc. Among them, MoO 3 has good performance for NH 3 detection.…”

Room-Temperature NH3 Sensors Based on Polyaniline-Assembled Graphitic Carbon Nitride Nanosheets

“…To today, researchers have developed a variety of sensitive materials for NH 3 , including MOS (SnO 2, WO 3, MoO 3 , etc. ), transition-metal sulfides (WS 2 , MoS 2 , SnS 2 , etc.…”