MoS₂/MoO₃ Nanocomposite for Selective NH₃ Detection in a Humid Environment

Abstract

Designing a material with novel sensing properties under extreme working conditions has remained a challenging task. Here, we report a facile two-step approach to develop a MoS 2 /MoO 3 composite with enhanced surface properties. When used as a gas sensor at 25 °C, it displayed superior sensing properties, selectivity, and a stable response toward ammonia against various reducing and oxidizing gases under highly humid conditions (relative humidity ≈ 95%). The composite exhibited a relative response of ≈55% (15% for 1 ppm) toward 50 ppm of NH 3 with smaller response τ res. and recovery τ rev. times of 45 and 53 s, respectively. It also displayed complete recovery without any external optical or thermal stimulus. The enhanced sensing properties of the composite are attributed to the synergistic effect arising from heterostructure formation between two base materials. The sensor displayed a decrease in resistance when exposed to NH 3 , a reducing gas, thus indicating its n-type character, which was further confirmed by performing Mott−Schottky (MS) measurements on MoS 2 and the MoS 2 /MoO 3 composite, both displaying n-type behavior with increased electron densities of the composite. Further, to understand the adsorption process and the resulting sensing properties, density functional theory simulations were performed using a pristine and a defect-enriched MoS 2 /MoO 3 surface. Large negative adsorption energies (for NH 3 ) of −344 and −519 meV, respectively, reflect that the adsorption process is feasible, and mechanism change from physisorption to chemisorption is predicted. Bader scheme was employed to evaluate the charge transfer between the NH 3 molecule and the pristine (defect-enriched) MoS 2 /MoO 3 surface and gave an amount of 0.073e (0.010e). Therefore, these results collectively justify the use of the MoS 2 /MoO 3 composite as a selective NH 3 sensor that can operate in humid air and environmental monitoring applications where such conditions exist.

NiWO4 Microflowers on Multi-Walled Carbon Nanotubes for High-Performance NH3 Detection

“…Due to the p–n junction, electrons flow from NiWO 4 to MWCNTs and then diffuse to NiWO 4 , and the grain boundary barrier is formed. As it enters and leaves the chamber, oxygen ions exchange electrons on the surface, thus alternately increasing and decreasing the depletion layer thickness. − These electrons then transfer to the neighboring large NiWO 4 particles and participate in the chemical reaction, further enhancing the gas sensing performance of the NiWO 4 MFs–MWCNTs sensor. Ideally, effective adsorption sites in the MWCNT bundle include exposed surfaces, gaps, and grooves formed between MWCNTs.…”

Field Effect Transistor Sensors Based on In‐Plane 1T′/2H/1T′ MoTe2 Heterophases with Superior Sensitivity and Output Signals

“…The sensor's responses become stabilized over time, proving the 1T′/2H sensor's long‐term stability. Figure 4f compares the NH 3 sensing results of the 1T′/2H/1T′ sensor with those from recent representative NH 3 sensors made of Ti 3 C 2 T x, [ 30 ] SnO 2 nanoparticles, [ 31 ] MoS 2 /MoO 3, [ 32 ] MoS 2, [ 33 ] NiWO 4 /CNT, [ 34 ] WS 2, [ 35 ] M‐CNTs, [ 36 ] Cs 3 Bi 2 I 6 Br 3, [ 37 ] and RGO/CuO. [ 38 ] The detection limit and operating current of our 1T′/2H/1T′ sensor outperform most of these NH 3 sensors.…”

MnMoO4-S nanosheets with rich oxygen vacancies for high-performance supercapacitors

“…6c correspond to the 3d 3/2 and 3d 5/2 electron orbits of Mo 6+ , respectively, which demonstrate that Mo mainly exists in the form of Mo 6+ ; 39,40 the peaks at the lower binding energies of 234.30 eV and 231.14 eV correspond to the 3d 3/2 and 3d 5/2 electron orbitals of Mo 5+ , respectively, indicating the existence of Mo 5+ ; 41 The peaks at the lower binding energies of 232.68 eV and 230.59 eV correspond to the 3d 3/2 and 3d 5/2 orbitals of Mo 4+ , respectively, and the obvious peaks at the lower binding energies of 225.06 eV correspond to the 2s orbital of S 2− . 42–44 In Fig. 6d, the absorption peaks of binding energies 532.17 eV, 530.79 eV, and 529.81 eV correspond to surface hydroxyl group, oxygen vacancy, and lattice oxygen, respectively.…”