Gas Sensing Performances of ZnO Hierarchical Structures for Detecting Dissolved Gases in Transformer Oil: A Mini Review

Abstract

Power transformer is one of the critical and expensive apparatus in high voltage power system. Hence, using highly efficient gas sensors to real-time monitor the fault characteristic gases dissolved in transformer oil is in pressing need to ensure the smooth functionalization of the power system. Till date, as a semiconductor metal oxide, zinc oxide (ZnO) is considered as the promising resistive-type gas sensing material. However, the elevated operating temperature, slow response, poor selectivity and stability limit its extensive applications in the field of dissolved gases monitoring. In this respect, rigorous efforts have been made to offset the above-mentioned shortcomings by multiple strategies. In this review, we first introduce the various ZnO hierarchical structures which possess high surface areas and less aggregation, as well as their corresponding gas sensing performances. Then, the primary parameters (sensitivity, selectivity and stability) which affect the performances of ZnO hierarchical structures based gas sensors are discussed in detail. Much more attention is particularly paid to the improvement strategies of enhancing these parameters, mainly including surface modification, additive doping and ultraviolet (UV) light activation. We finally review gas sensing mechanism of ZnO hierarchical structure based gas sensor. Such a detailed study may open up an avenue to fabricate sensor which achieve high sensitivity, good selectivity and long-term stability, making it a promising candidate for transformer oil monitor.

Hyperbranched hierarchical nanoarchitectures of ZnOHF: synthesis, characterization, growth mechanism and their gas sensing property

“…The sensing performances to ethanol of sample S3 are comparable to the pure ZnO-based materials reported in the literature, such as the brush-like hierarchical ZnO nanostructures [37], and the mesoporous rhombic ZnO nanorod arrays [34]. However, it should be admitted that the gas sensing performance in the current study is not outstanding compared to the state of the art in the field [32,33]. Higher response and better selectivity are required for real applications.…”

“…In addition to surface reactions, surface adsorption and surface diffusion play important roles in gas sensing [33]. In this work, sample S2 has a higher splitting degree than S3.…”

“…3 The time-dependent morphology evolution of the ZnOHF nanoarchitectures prepared at the CTAB concentration of 0.05 mol/L and the temperature of 120 °C, confirming the crystal splitting mechanism can be demonstrated in this work that the gas sensing properties of ZnOHF hyperbranched hierarchical nanoarchitectures may be varied according to their splitting degrees. Currently, great research efforts have been focused on the gas sensors constructed with metal oxide semiconductors, among which ZnO nanostructures have received extensive attention from both academic and industrial fields [32,33]. In particular, it is noticed in a previous report in the literature that the gas sensor based on the ZnO nanorod arrays showed high performance in ethanol detection [34].…”

A Review of Microwave Synthesis of Zinc Oxide Nanomaterials: Reactants, Process Parameters and Morphologies

“…Examples of various morphologies of ZnO are presented in Figure 17 , Figure 18 , Figure 19 and Figure 20 . The modification of morphology of ZnO NMs with a 3D architecture is extremely important e.g., for producing sensors with high sensing capabilities [ 739 ]. The 3D architecture of ZnO NMs, characterised by a small particle size, a high specific surface area and porosity, enables the improvement of the sensing response of gas sensors [ 152 ].…”

Recent Advances in ZnO-Based Carbon Monoxide Sensors: Role of Doping

“…Metal oxide semiconductors (MOSs) have been successfully used to detect CO gas. MOSs have low cost, high sensitivity [ 24 , 25 , 26 , 27 , 28 , 29 , 30 ], convenient operation, a rapid response and recovery time, high physical and chemical stabilities [ 22 ], excellent electrical performance [ 16 ], and a simple and portable design [ 2 ]. Among various MOSs, those based on ZnO have become widely manufactured and utilized because of their outstanding characteristics, such as a bandgap around 3.4 eV at room temperature [ 31 , 32 , 33 ], high optical transparency in the visible region (>80%), n-type conductivity, and high exciton binding energy in the order of 60 meV [ 31 , 34 ].…”