Synthesis of Ti3C2Tx-derived and layered TiO2 with NiO nanosheets as heterojunction composites and their gas-sensing properties

Abstract

As a p-type metal oxide semiconductor gas-sensing material, NiO has a fast response rate and excellent moisture resistance. However, the practical application of NiO gas sensor has been limited due to its low response and poor selectivity. In this study, the gas sensing capabilities of the NiO-based sensor were enhanced by increasing the variation of hole concentration on the surface of NiO. Vertically grown 2D/2D p-NiO/n-TiO₂ nanosheets were prepared by growing p-type NiO on n-type TiO₂ derived from layered Ti₃C₂T_x (T=-F, -O and -OH) MXene via a hydrothermal method. The addition of n-TiO₂ not only reduces the agglomeration of NiO nanosheets and increases the adsorption sites for a target gas, but also forms p-n junctions at the interface between TiO₂ and NiO. It reduces the hole concentrations on the NiO surface, enhancing the response and selectivity of the NiO gas sensor. The NiO/TiO₂ gas sensor response is about 12-fold than NiO in 100 ppm acetone at 340 ℃, and it shows remarkable selectivity. This work presents a novel approach to improve the gas-sensing properties of p-type metal oxide semiconductors.