Enhanced NH3 sensing performance at ppb level derived from Ti3C2Tx-supported ZnTi-LDHs nanocomposite with similar metal-semiconductor heterostructure

Layered double hydroxides (LDHs) are attracting increased attention in the field of gas sensor owing to their high specific surface and interlayer modifiability. However, the general tendency to restacking and poor conductivity significantly affect the performance of the gas sensor based on LDHs towards rarefied gas. To resolve these problems, we successfully constructed the MXene (Ti3C2Tx)-supported ZnTi-LDHs (LDHs/Ti3C2Tx) nanocomposite with loose heterostructure by one-step hydrothermal method based on electrostatic ordered selfassembly. The LDHs uniformly wrapped on Ti3C2Tx nanosheets form a highly synergistic similar metalsemiconductor contact with Ti3C2Tx, and the formed anti-barrier layer (ABL) has a trapping effect on the electrons generated by NH3-sensing. Meanwhile, the formation of tiny LDHs might be ascribed to the effect of Ti atoms in Ti3C2Tx, which is confirmed by first-principles calculations. Benefiting from similar metalsemiconductor heterostructure and the effect of Ti atoms in Ti3C2Tx, the electrical conductivity and the adsorption active sites are prominently improved, which are essential for the enhancement of sensitivity to rarefied gas. The gas sensor based on ZnTi-LDHs/Ti3C2Tx nanocomposite exhibits about 5 and 9-fold enhancement in response value to 50 ppm NH3 at room temperature (RT) compared with the pure LDHs and Ti3C2Tx, respectively. Notably, the as-fabricated gas sensor could detect as low as 100 ppb NH3 with a response of 1.26 at RT. Furthermore, the LDHs/Ti3C2Tx sensor exhibits fast response/recovery time, high selectivity, acceptable humidity tolerance and outstanding long-term stability towards NH3. Above all, this work provides a feasible route to develop excellent gas-sensing materials of sensor via interfacial design.

Automated summary

LDHs are attracting attention in gas sensor field due to high specific surface and modifiability, but restacking and poor conductivity hinder performance. By constructing LDHs/Ti3C2Tx nanocomposite, conductivity and adsorption sites are improved, resulting in enhanced sensitivity to rarefied gas. The new gas sensor shows significant enhancement in response value to NH3 at room temperature, with fast response time, high selectivity and long-term stability.