H2S/Butane Dual Gas Sensing Based on a Hydrothermally Synthesized MXene Ti3C2Tx/NiCo2O4 Nanocomposite

Abstract

Real-time sensing of hydrogen sulfide (H₂S) at room temperature is important to ensure the safety of humans and the environment. Four kinds of different nanocomposites, such as MXene Ti₃C₂T_x, Ti₃AlC₂, WS₂, and MoSe₂/NiCo₂O₄, were synthesized using the hydrothermal method in this paper. Initially, the intrinsic properties of the synthesized nanocomposites were studied using different techniques. P-type butane and H₂S-sensing behaviors of nanocomposites were performed and analyzed deeply. Four sensor sheets were fabricated using a spin-coating method. The gas sensor was distinctly part of the chemiresistor class. The MXene Ti₃C₂T_x/NiCo₂O₄-based gas sensor detected the highest response (16) toward 10 ppm H₂S at room temperature. In comparison, the sensor detected the highest response (9.8) toward 4000 ppm butane at 90 °C compared with the other three fabricated sensors (Ti₃AlC₂, WS₂, and MoSe₂/NiCo₂O₄). The MXene Ti₃C₂T_x/NiCo₂O₄ sensor showed excellent responses, minimum limits of detection (0.1 ppm H₂S and 5 ppm butane), long-term stability, and good reproducibility compared with the other fabricated sensors. The highest sensing properties toward H₂S and butane were accredited to p-p heterojunctions, higher BET surface areas, increased oxygen species, etc. These simply synthesized nanocomposites and fabricated sensors present a novel method for tracing H₂S and butane at the lowest concentration to prevent different gas-exposure-related diseases.

Keywords: MXene Ti3C2Tx; butane sensing; ppb-level H2S-sensing; sensor sheets; spherical NiCo2O4.

Figure 1

XRD patterns of MXene Ti₃C₂T_x/NiCo₂O₄, Ti₃AlC₂/NiCo₂O₄, WS₂/NiCo₂O₄, and MoSe₂/NiCo₂O₄.

Figure 2

SEM images and EDS (spectrum/scattering) of MXene/NiCo₂O₄ (a), Ti₃AlC₂/NiCo₂O₄ (b), WS₂/NiCo₂O₄ (c), and MoSe₂/NiCo₂O₄ (d).

Figure 3

TEM and HRTEM images of MXene/NiCo₂O₄ (a), Ti₃AlC₂/NiCo₂O₄ (b), WS₂/NiCo₂O₄, (c) and MoSe₂/NiCo₂O₄ (d).

Figure 4

N₂ adsorption–desorption isotherms and pore size distributions of MXene/NiCo₂O₄, Ti₃AlC₂/NiCo₂O₄, WS₂/NiCo₂O₄, and MoSe₂/NiCo₂O₄ (a,b) and the FTIR spectrum of MXene/NiCo₂O₄ (c).

Figure 5

XPS spectra of the full spectrum (a), Ni 2p (b), Co 2p (c), O 1s (d), (Ti 2p (e), and C 1s (f) spectra of MXene/NiCo₂O₄.

Figure 6

Resistance changes in the MXene/NiCo₂O₄ composite-based gas sensor for different concentrations of butane at 90 °C (a–c) and the relationship between the response of MXene/NiCo₂O₄ and different RHs at 90 °C (d).

Figure 7

Resistance changes in the MXene/NiCo₂O₄ composite-based gas sensor at different concentrations of H₂S at room temperature (a–c) and the relationship between the response of MXene/NiCo₂O₄ and different RH at room temperature (d).

Figure 8

Responses of MXene/NiCo₂O₄ to 10 ppm H₂S and 4000 ppm butane at different operating temperatures.

Figure 9

The reproducibility of the gas sensors based on MXene/NiCo₂O₄, Ti₃AlC₂/NiCo₂O₄, WS₂/NiCo₂O₄, and MoSe₂/NiCo₂O₄ to 4000 ppm butane at 90 °C (a) and 10 ppm H₂S at room temperature (b).

Figure 10

The stability of the gas sensors based on MXene/NiCo₂O₄, Ti₃AlC₂/NiCo₂O₄, WS₂/NiCo₂O₄, and MoSe₂/NiCo₂O₄ to 4000 ppm butane at 90 °C (a) and 10 ppm H₂S at room temperature (b).

Figure 11

The cross-selectivity of the MXene/NiCo₂O₄-, Ti₃AlC₂/NiCo₂O₄-, WS₂/NiCo₂O₄- and MoSe₂/NiCo₂O₄-based gas sensors for 10 ppm gases at room temperature (a) and for 5 ppm gases at 90 °C (b).

Figure 12

Relationship between the response of MXene/NiCo₂O₄ and H₂S concentrations at room temperature (a) and the relationship between the response of MXene/NiCo₂O₄ and butane concentrations at 90 °C (b).

Figure 13

Gas sensing mechanism and energy band diagram of MXene/NiCo₂O₄ (a,b).

Figure 13

Gas sensing mechanism and energy band diagram of MXene/NiCo₂O₄ (a,b).

Figure 14

The synthesis method and the sensor fabrication method.