Room-Temperature Ammonia Gas Sensing Using Mixed-Valent CuCo₂O₄ Nanoplatelets: Performance Enhancement through Stoichiometry Control

Abstract

We report the sensing properties of an interesting ternary oxide CuCo 2 O 4 (CCO) which comprises two earth-abundant transition elements, both capable of supporting multiple valence states. We have used a synthesis protocol, which renders unique nanoplatelet-type morphology but with a degree of biphasic character (CuO as a secondary phase in addition to the defect-spinel Cu 1– x Co 2 O 4 ). This sample constitution can be controlled through the use of cation off-stoichiometry, and the same also influence the sensing response significantly. In particular, a Co 10 at. % excess CCO (CCO–Co(10)) case exhibits a good response (∼7.9% at 400 ppm) for NH 3 gas with a complete recovery at room temperature (23 °C, ±1 °C) in 57% RH. The material performance was investigated for other gases such as H 2 S, NO 2 , and CO. A good response is observed for H 2 S and NO 2 gases but without a recovery; however, for CO, a poor response is noted. Herein, we discuss the specific results for ammonia sensing for the CCO–Co(10) case in detail via the use of different characterizations and outline the difference between the cases of the single-phase defect-stabilized material versus nonpercolating biphasic material.

Advances in designs and mechanisms of semiconducting metal oxide nanostructures for high-precision gas sensors operated at room temperature

“…Doping of metal ions in SMONs can increase the number of active sites and defects on the surface of SMON nanocrystals, and thus enhance the amount of oxygen species and increase the adsorbed gas molecules on the sensor's surface. Therefore, the gas sensing performance of the SMONs can be effectively improved by doping of metal ions including Al 3+ , 117,271 Cu 2+ , 272,273 Zn 2+ , 274 Ni 2+ , 275,276 Co 3+ , 277,278 Fe 3+ , 279 Mg 2+ 280 and Sb 5+ . 281 The recent key sensing applications of RT gas sensors using this method are summarized in Table 4.…”

Ultrathin MoOx/Graphene Hybrid Field Effect Transistor Sensors Prepared Simply by a Shadow Mask Approach for Selective ppb‐Level NH3 Sensing with Simultaneous Superior Response and Fast Recovery

“…A similar effect of humidity on NH 3 has also been observed in the bottom gate graphene FET and metal oxide based chemiresistor sensors. [ 19 ] Close inspection reveals that the recovery time elongates with the increase in humidity. The recovery ratios calculated as ( I gas − I end )/( I gas − I air ) are observed to decrease (increase) with the humidity (area coverage) for all the sensors.…”

Sputtering Power and Annealing Effects on the Properties of Zn2SnO4–SnO2 Composite Thin Film for Pungent Smelling Gas (NH3) Detection

“…It is observed that the Zn 2 SnO 4 -SnO 2 composite film showed a high SR to NH 3 gas compared with other composite thin filmbased NH 3 sensors reported in the literature (Table 4). [16,[44][45][46][47][48][49] This may be due to the presence of more number of oxygen ions on the surface of the film. [26] The high SR of the film to NH 3 made it as a hopeful material for the NH 3 gas sensor at room-temperature working condition.…”

“…The requirement of room-temperature NH 3 sensor directed the researchers toward the development of sensing material to be operated at room temperature. [16] Due to this a lot of room-temperature NH 3 sensors are developed recently. [3,[17][18][19][20] Despite that, the reports on room-temperature NH 3 sensors based on ZnO-SnO 2 composite material are limited.…”