The effective detection of harmful gases using low-cost gas sensors plays key roles in public health, environmental protection, and industrial safety. Among them, metal oxide-based (MOXs) chemiresistive gas sensors are gaining importance in environmental monitoring, food safety detection, and healthcare diagnosis due to their easy integration and cost-effectively. Nevertheless, MOXs commonly need to operate at high temperatures (100-500 oC) to overcome the energy barriers of redox reactions, resulting in high power consumption, poor safety, and operational stability. In addition, the high working temperature requires the heater unit, leading to increased costs and complexity in the fabrication process. Consequently, gas sensors that function at RT have garnered significant attention. Designing unique morphology, catalyst (metal elements, metal oxides, etc.) decoration, constructing hetero-structures, and coupling carbon-based nanomaterials have been reported to realize the RT response of MOXs to H2S, NO2, and NH3. However, achieving rapid detection of volatile organic compounds with high sensitivity and selectivity at RT using MOXs without catalysts remains challenging, as well as revealing the gas sensing mechanism.
Oxygen vacancy engineering has been employed to improve the surface activity and electronic structure of MOXs, thereby enhancing their performance in hetero-catalysis, energy storage, and gas sensing applications. Notably, the presence of oxygen vacancies can supply free electrons and serve as active sites for the adsorption of molecules, thus influencing the capacity to capture electrons and reduce reaction barriers, all of which are paramount in enhancing the efficacy of sensing materials. Hence, regulating the electronic properties and surface activity of MOXs is crucial for realizing RT-sensing functions. Exactly, controlling the oxygen vacancy of metal oxide is a promising approach for developing high-performance RT gas sensors, but it is also urgent to offer insight into the improved LOD and response and recovery speed enabled by oxygen vacancy.
Recently, a team of material scientists led by Chao Zhang from Yangzhou University, China presents a universal design princip le of oxygen vacancy-engineered interfacial redox kinetics and offers new mechanistic insights into moderate electronic structure and improved charge transfer kinetic at the gas-solid interface. This work will enrich the activity-functions relationship of metal oxide catalysts and enable ultrasensitive and rapid VOCs detection anytime and anywhere using portable devices.
The team published their work in Journal of Advanced Ceramics on May 27, 2025.
"In this work, to overcome the sluggish kinetics and imbalanced adsorption/desorption of MoO3, the synergetic strengthen strategy of oxygen vacancy and 1D nanostructure for enabling room temperature biomarker detection was developed.", said Prof. Chao Zhang, the leader of Jiangsu Key Laboratory of Surface Strengthening and Functional Manufacturing (Yangzhou University). Rich oxygen vacancy-MoO3-x (MoO3-x-R) demonstrated significantly enhanced TMA sensing properties at 22 oC, including high response (0 → 7.6 @ 20 ppm), fast response/recovery speed (60/90 s), excellent selectivity, low LOD (400 ppb), and enduring stability exceeding 28 days.
"To gain the universal enhanced mechanisms, the improved electronic structure, surface redox, and charge transfer kinetics by oxygen vacancy engineering were elucidated through experimental, DFT, and MD studies. Their comprehensive studies revealed that the rich oxygen vacancy enables accelerated charge transfer, superior redox capacity, and improved adsorption/desorption kinetics, thus significantly improving the sensitivity, LOD, and response/recovery speed.", said Prof. Chao Zhang.
Meanwhile, the research team is optimistic about the application potential of their work. The practicability of the portable sensor device was also demonstrated towards food safety detection. "The on-field detection tests manifested that the device was capable of quantitively TMA monitoring and rapid & non-destructive fish freshness detection. This work will contribute to developing high-performance VOC sensors.", said Prof. Chao Zhang.
In future, to gain the deeper principle and broad application of MOS based gas sensors, the research team will focus on the In-situ analysis of activity-functions relationship of metal oxide and boosted sensing performance and machine learning driven smart gas sensors.
This work is supported by the National Natural Science Foundation of China under Grant No. 52402202 and the Natural Science Youth Foundation of Jiangsu Province of China under Grant No. BK20240933.
About Author
Chao Zhang received a joint Ph.D. degree from Technology University of Belfort Montbéliard (France) and Xi'an Jiaotong University (China) in June 2008. From September 2007 to January 2009, he worked as a teaching-research assistant in Technology University of Belfort-Montbéliard. Since 2009, he is a postdoctoral researcher, and then a senior researcher in Materials Science Department of Engineering School of University of Mons (Belgium). He joined Yangzhou University (China) as professor in 2014 and became the Dean of College of Mechanical Engineering in 2022. His research interests include thermal-sprayed techniques and functional coatings, especially gas sensing and wear-resistant coatings.
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen . JAC's 2024 IF is 16.6, ranking in Top 1 (1/33, Q1) among all journals in "Materials Science, Ceramics" category, and its 2024 CiteScore is 25.9 (5/130) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
