Advanced Strategies to Improve Performances of Molybdenum-Based Gas Sensors

W/Mo/Cr Doping Modulates the Negative-Positive Inversion Gas Sensing Behavior of VO2(M1)

The anomalous gas sensing behavior has garnered significant attention from researchers, prompting a re-evaluation of the gas sensing theory. This work focuses on inversion gas sensing behavior induced by element doping. W/Mo/Cr-doped VO2(M1) samples are synthesized, and their sensing behaviors are investigated. The results show that the elements can modulate the sensing behavior with an opposite orientation. The sensing behavior in the opposite orientation is attributed to the extent of the reduced Fermi level of VO2(M1) after doping. W-doped VO2(M1) maintains a resistance-decreased sensing behavior (-n). In contrast, the decrease in Fermi level results in the formation of a Schottky barrier between the gas-absorbed Mo/Cr-doped VO2(M1) and the electrode. The formation of Schottky barriers leads to the inversion sensing behavior, which feedbacks as an increased resistance (-p). This study offers a novel perspective on the gas sensing theory.

Emerging Low Detection Limit of Optically Activated Gas Sensors Based on 2D and Hybrid Nanostructures

Gas sensing is essential for detecting and measuring gas concentrations across various environments, with applications in environmental monitoring, industrial safety, and healthcare. The integration of two-dimensional (2D) materials, organic materials, and metal oxides has significantly advanced gas sensor technology, enhancing its sensitivity, selectivity, and response times at room temperature. This review examines the progress in optically activated gas sensors, with emphasis on 2D materials, metal oxides, and organic materials, due to limited studies on their use in optically activated gas sensors, in contrast to other traditional gas-sensing technologies. We detail the unique properties of these materials and their impact on improving the figures of merit (FoMs) of gas sensors. Transition metal dichalcogenides (TMDCs), with their high surface-to-volume ratio and tunable band gap, show exceptional performance in gas detection, especially when activated by UV light. Graphene-based sensors also demonstrate high sensitivity and low detection limits, making them suitable for various applications. Although organic materials and hybrid structures, such as metal-organic frameworks (MoFs) and conducting polymers, face challenges related to stability and sensitivity at room temperature, they hold potential for future advancements. Optically activated gas sensors incorporating metal oxides benefit from photoactive nanomaterials and UV irradiation, further enhancing their performance. This review highlights the potential of the advanced materials in developing the next generation of gas sensors, addressing current research gaps and paving the way for future innovations.

Enhancing Defect-Induced Dipole Polarization Strategy of SiC@MoO3 Nanocomposite Towards Electromagnetic Wave Absorption

Defect engineering in transition metal oxides semiconductors (TMOs) is attracting considerable interest due to its potential to enhance conductivity by intentionally introducing defects that modulate the electronic structures of the materials. However, achieving a comprehensive understanding of the relationship between micro-structures and electromagnetic wave absorption capabilities remains elusive, posing a substantial challenge to the advancement of TMOs absorbers. The current research describes a process for the deposition of a MoO3 layer onto SiC nanowires, achieved via electro-deposition followed by high-temperature calcination. Subsequently, intentional creation of oxygen vacancies within the MoO3 layer was carried out, facilitating the precise adjustment of electromagnetic properties to enhance the microwave absorption performance of the material. Remarkably, the SiC@MO-t4 sample exhibited an excellent minimum reflection loss of - 50.49 dB at a matching thickness of 1.27 mm. Furthermore, the SiC@MO-t6 sample exhibited an effective absorption bandwidth of 8.72 GHz with a thickness of 2.81 mm, comprehensively covering the entire Ku band. These results not only highlight the pivotal role of defect engineering in the nuanced adjustment of electromagnetic properties but also provide valuable insight for the application of defect engineering methods in broadening the spectrum of electromagnetic wave absor ption effectiveness. SiC@MO-t samples with varying concentrations of oxygen vacancies were prepared through in-situ etching of the SiC@MoO3 nanocomposite. The presence of oxygen vacancies plays a crucial role in adjusting the band gap and local electron distribution, which in turn enhances conductivity loss and induced polarization loss capacity. This finding reveals a novel strategy for improving the absorption properties of electromagnetic waves through defect engineering.

Graphene-based chemiresistive gas sensors

Gas sensors allow the monitoring of the chemical environment of humans, which is often crucial for their wellbeing or even survival. Miniaturization, reversibility, and selectivity are some of the key challenges for serial use of chemical sensors. This tutorial review describes critical aspects when using nanomaterials as sensing substrates for the application in chemiresistive gas sensors. Graphene has been shown to be a promising candidate, as it allows gas sensors to be operated at room temperature, possibly saving large amounts of energy. In this review, an overview is given on the general mechanisms for gas-sensitive semiconducting materials and the implications of doping and functionalization on the sensing parameters of chemiresistive devices. It shows in detail how different challenges, like sensitivity, response time, reversibility and selectivity have been approached by material development and operation modes. In addition, perspectives from the area of data analysis and intelligent algorithms are presented, which can further enhance these sensors' usability in the field.

MoTe2/InN van der Waals heterostructures for gas sensors: a DFT study

Vertical van der Waals (vdW) heterostructures have shown potential for gas sensing owing to their remarkable sensitivity. However, the optimization process for achieving the best gas sensing performance is complicated by the heterostructure's reliance on both physical and electrical characteristics. This study employs density functional theory (DFT) to analyse the structural and electronic parameters of a MoTe2/InN vdW heterostructure. The findings of this study indicate that the vdW heterostructure has a type-II band alignment with higher adsorption energy towards NH3, NO2, and SO2 than the individual monolayers. In specific, the heterostructure is well suited for NO2 detection but has limitations in reliably detecting NH3 and SO2 due to longer recovery times. We find significant hybridization between the adsorbate and interacting surfaces' orbitals and a notable presence of NO2 molecular orbitals in proximity to the Fermi level. Additionally, dielectric and work function modulations offer a viable means to develop optical-based gas sensors that can selectively detect NO2. Our research provides valuable insights into vdW heterostructure design for high-performance gas sensors.

Wearable Nano-Based Gas Sensors for Environmental Monitoring and Encountered Challenges in Optimization

With a rising emphasis on public safety and quality of life, there is an urgent need to ensure optimal air quality, both indoors and outdoors. Detecting toxic gaseous compounds plays a pivotal role in shaping our sustainable future. This review aims to elucidate the advancements in smart wearable (nano)sensors for monitoring harmful gaseous pollutants, such as ammonia (NH3), nitric oxide (NO), nitrous oxide (N2O), nitrogen dioxide (NO2), carbon monoxide (CO), carbon dioxide (CO2), hydrogen sulfide (H2S), sulfur dioxide (SO2), ozone (O3), hydrocarbons (CxHy), and hydrogen fluoride (HF). Differentiating this review from its predecessors, we shed light on the challenges faced in enhancing sensor performance and offer a deep dive into the evolution of sensing materials, wearable substrates, electrodes, and types of sensors. Noteworthy materials for robust detection systems encompass 2D nanostructures, carbon nanomaterials, conducting polymers, nanohybrids, and metal oxide semiconductors. A dedicated section dissects the significance of circuit integration, miniaturization, real-time sensing, repeatability, reusability, power efficiency, gas-sensitive material deposition, selectivity, sensitivity, stability, and response/recovery time, pinpointing gaps in the current knowledge and offering avenues for further research. To conclude, we provide insights and suggestions for the prospective trajectory of smart wearable nanosensors in addressing the extant challenges.

Tunnel junction sensing of TATP explosive at the single-molecule level

Triacetone triperoxide (TATP) is a highly potent homemade explosive commonly used in terrorist attacks. Its detection poses a significant challenge due to its volatility, and the lack of portability of current sensing techniques. To address this issue, we propose a novel approach based on single-molecule TATP detection in the air using a device where tunneling current in N-terminated carbon-nanotubes nanogaps is measured. By employing the density functional theory combined with the non-equilibrium Green's function method, we show that current of tens of nanoamperes passes through TATP trapped in the nanogap, with a discrimination ratio of several orders of magnitude even against prevalent indoor volatile organic compounds (VOCs). This high tunneling current through TATP's highest occupied molecular orbital (HOMO) is facilitated by the strong electric field generated by N-C polar bonds at the electrode ends and by the hybridization between TATP and the electrodes, driven by oxygen atoms within the probed molecule. The application of the same principle is discussed for graphene nanogaps and break-junctions.

Fundamentals, rational catalyst design, and remaining challenges in electrochemical NOx reduction reaction

Nitrogen oxides (NOx) emissions carry pernicious consequences on air quality and human health, prompting an upsurge of interest in eliminating them from the atmosphere. The electrochemical NOx reduction reaction (NOxRR) is among the promising techniques for NOx removal and potential conversion into valuable chemical feedstock with high conversion efficiency while benefiting energy conservation. However, developing efficient and stable electrocatalysts for NOxRR remains an arduous challenge. This review provides a comprehensive survey of recent advancements in NOxRR, encompassing the underlying fundamentals of the reaction mechanism and rationale behind the design of electrocatalysts using computational modeling and experimental efforts. The potential utilization of NOxRR in a Zn-NOx battery is also explored as a proof of concept for concurrent NOx abatement, NH3 synthesis, and decarbonizing energy generation. Despite significant strides in this domain, several hurdles still need to be resolved in developing efficient and long-lasting electrocatalysts for NOx reduction. These possible means are necessary to augment the catalytic activity and electrocatalyst selectivity and surmount the challenges of catalyst deactivation and corrosion. Furthermore, sustained research and development of NOxRR could offer a promising solution to the urgent issue of NOx pollution, culminating in a cleaner and healthier environment.

Conductometric Gas Sensor Based on MoO3 Nanoribbon Modified with rGO Nanosheets for Ethylenediamine Detection at Room Temperature

An ethylenediamine (EDA) gas sensor based on a composite of MoO3 nanoribbon and reduced graphene oxide (rGO) was fabricated in this work. MoO3 nanoribbon/rGO composites were synthesized using a hydrothermal process. The crystal structure, morphology, and elemental composition of MoO3/rGO were analyzed via XRD, FT-IR, Raman, TEM, SEM, XPS, and EPR characterization. The response value of MoO3/rGO to 100 ppm ethylenediamine was 843.7 at room temperature, 1.9 times higher than that of MoO3 nanoribbons. The MoO3/rGO sensor has a low detection limit (LOD) of 0.235 ppm, short response time (8 s), good selectivity, and long-term stability. The improved gas-sensitive performance of MoO3/rGO composites is mainly due to the excellent electron transport properties of graphene, the generation of heterojunctions, the higher content of oxygen vacancies, and the large specific surface area in the composites. This study presents a new approach to efficiently and selectively detect ethylenediamine vapor with low power.

Heteroatom-Doped Molybdenum Disulfide Nanomaterials for Gas Sensors, Alkali Metal-Ion Batteries and Supercapacitors

Molybdenum disulfide (MoS2) is the second two-dimensional material after graphene that received a lot of attention from the research community. Strong S-Mo-S bonds make the sandwich-like layer mechanically and chemically stable, while the abundance of precursors and several developed synthesis methods allow obtaining various MoS2 architectures, including those in combinations with a carbon component. Doping of MoS2 with heteroatom substituents can occur by replacing Mo and S with other cations and anions. This creates active sites on the basal plane, which is important for the adsorption of reactive species. Adsorption is a key step in the gas detection and electrochemical energy storage processes discussed in this review. The literature data were analyzed in the light of the influence of a substitutional heteroatom on the interaction of MoS2 with gas molecules and electrolyte ions. Theory predicts that the binding energy of molecules to a MoS2 surface increases in the presence of heteroatoms, and experiments showed that such surfaces are more sensitive to certain gases. The best electrochemical performance of MoS2-based nanomaterials is usually achieved by including foreign metals. Heteroatoms improve the electrical conductivity of MoS2, which is a semiconductor in a thermodynamically stable hexagonal form, increase the distance between layers, and cause lattice deformation and electronic density redistribution. An analysis of literature data showed that co-doping with various elements is most attractive for improving the performance of MoS2 in sensor and electrochemical applications. This is the first comprehensive review on the influence of foreign elements inserted into MoS2 lattice on the performance of a nanomaterial in chemiresistive gas sensors, lithium-, sodium-, and potassium-ion batteries, and supercapacitors. The collected data can serve as a guide to determine which elements and combinations of elements can be used to obtain a MoS2-based nanomaterial with the properties required for a particular application.

Recent development of metal oxides and chalcogenides as antimicrobial agents

Pathogenic microbes are a major concern in hospitals and other healthcare facilities because they affect the proper performance of medical devices, surgical devices, etc. Due to the antimicrobial resistance or multidrug resistance, combatting these microbial infections has grown to be a significant research area in science and medicine as well as a critical health concern. Antibiotic resistance is where microbes acquire and innately exhibit resistance to antimicrobial agents. Therefore, the development of materials with promising antimicrobial strategy is a necessity. Amongst other available antimicrobial agents, metal oxide and chalcogenide-based materials have shown to be promising antimicrobial agents due to their inherent antimicrobial activity as well as their ability to kill and inhibit the growth of microbes effectively. Moreover, other features including the superior efficacy, low toxicity, tunable structure, and band gap energy has makes metal oxides (i.e. TiO₂, ZnO, SnO₂ and CeO₂ in particular) and chalcogenides (Ag₂S, MoS₂, and CuS) promising candidates for antimicrobial applications as illustrated by examples discussed in this review.

The versatile family of molybdenum oxides: synthesis, properties, and recent applications

The family of molybdenum oxides has numerous advantages that make them strong candidates for high-value research and various commercial applications. The variation of their multiple oxidation states allows their existence in a wide range of compositions and morphologies that converts them into highly versatile and tunable materials for incorporation into energy, electronics, optical, and biological systems. In this review, a survey is presented of the most general properties of molybdenum oxides including the crystalline structures and the physical properties, with emphasis on present issues and challenging scientific and technological aspects. A section is devoted to the thermodynamical properties and the most common preparation techniques. Then, recent applications are described, including photodetectors, thermoelectric devices, solar cells, photo-thermal therapies, gas sensors, and energy storage.

Self-Powered Nitrogen Dioxide Sensor Based on Pd-Decorated ZnO/MoSe2 Nanocomposite Driven by Triboelectric Nanogenerator

This paper introduces a high-performance self-powered nitrogen dioxide gas sensor based on Pd-modified ZnO/MoSe₂ nanocomposites. Poly(vinyl alcohol) (PVA) nanofibers were prepared by high-voltage electrospinning and tribological nanogenerators (TENGs) were designed. The output voltage of TENG and the performance of the generator at different frequencies were measured. The absolute value of the maximum positive and negative voltage exceeds 200 V. Then, the output voltage of a single ZnO thin-film sensor, Pd@ZnO thin-film sensor and Pd@ZnO/MoSe₂ thin-film sensor was tested by using the energy generated by TENG at 5 Hz, when the thin-film sensor was exposed to 1-50 ppm NO₂ gas. The experimental results showed that the sensing response of the Pd@ZnO/MoSe₂ thin-film sensor was higher than that of the single ZnO film sensor and Pd@ZnO thin-film sensor. The TENG-driven response rate of the Pd@ZnO/MoSe₂ sensor on exposure to 50 ppm NO₂ gas was 13.8. At the same time, the sensor had good repeatability and selectivity. The synthetic Pd@ZnO/MoSe₂ ternary nanocomposite was an ideal material for the NO₂ sensor, with excellent structure and performance.

MOF/Polymer-Integrated Multi-Hotspot Mid-Infrared Nanoantennas for Sensitive Detection of CO2 Gas

Metal-organic frameworks (MOFs) have been extensively used for gas sorption, storage and separation owing to ultrahigh porosity, exceptional thermal stability, and wide structural diversity. However, when it comes to ultra-low concentration gas detection, technical bottlenecks of MOFs appear due to the poor adsorption capacity at ppm-/ppb-level concentration and the limited sensitivity for signal transduction. Here, we present hybrid MOF-polymer physi-chemisorption mechanisms integrated with infrared (IR) nanoantennas for highly selective and ultrasensitive CO₂ detection. To improve the adsorption capacity for trace amounts of gas molecules, MOFs are decorated with amino groups to introduce the chemisorption while maintaining the structural integrity for physisorption. Additionally, leveraging all major optimization methods, a multi-hotspot strategy is proposed to improve the sensitivity of nanoantennas by enhancing the near field and engineering the radiative and absorptive loss. As a benefit, we demonstrate the competitive advantages of our strategy against the state-of-the-art miniaturized IR CO₂ sensors, including low detection limit, high sensitivity (0.18%/ppm), excellent reversibility (variation within 2%), and high selectivity (against C₂H₅OH, CH₃OH, N₂). This work provides valuable insights into the integration of advanced porous materials and nanophotonic devices, which can be further adopted in ultra-low concentration gas monitoring in industry and environmental applications.

ZnO-based antimicrobial coatings for biomedical applications

Rapid transmission of infectious microorganisms such as viruses and bacteria through person-to-person contact has contributed significantly to global health issues. The high survivability of these microorganisms on the material surface enumerates their transmissibility to the susceptible patient. The antimicrobial coating has emerged as one of the most interesting technologies to prevent growth and subsequently kill disease-causing microorganisms. It offers an effective solution a non-invasive, low-cost, easy-in-use, side-effect-free, and environmentally friendly method to prevent nosocomial infection. Among antimicrobial coating, zinc oxide (ZnO) stands as one of the excellent materials owing to zero toxicity, high biocompatibility to human organs, good stability, high abundancy, affordability, and high photocatalytic performance to kill various infectious pathogens. Therefore, this review provides the latest research progress on advanced applications of ZnO nanostructure-based antibacterial coatings for medical devices, biomedical applications, and health care facilities. Finally, future challenges and clinical practices of ZnO-based antibacterial coating are addressed.

CsPbBr3-Based Nanostructures for Room-Temperature Sensing of Volatile Organic Compounds

All-inorganic halide perovskites, as a dominant member of the perovskite family, have been proven to be excellent semiconductors due to the great successes for solar cells, light-emitting diodes, photodetectors, and nanocrystal photocatalysts. Despite the remarkable advances in those fields, there are few research studies focusing on gas and humidity-sensing performances, especially for pure CsPbBr₃ and heterogeneous CsPbBr₃@MoS₂ composites. Here, we first report a valuable CsPbBr₃ sensor prepared by electrospinning, and the excellent gas sensing performances are investigated. The CsPbBr₃ sensor can quickly and effectively detect ethanolamine at room temperature. The response time is only 16 s, and the response to 100 ppm ethanolamine is as high as 29.87, besides the excellent repeatability and good stability. The theoretical detection limit is estimated to be 21 ppb. Furthermore, considering the irreplaceable role of heterostructures in regulating the electronic structure and supporting rich reaction boundaries, we also actively explored the EA sensitivity of inorganic CsPbBr₃-based heterogeneous composites CsPbBr₃@MoS₂. At the same time, the roles of the critical capping agents OA and OAm are systematically investigated. This work demonstrates the great potential of all-inorganic halide perovskites in promising volatile organic compound detection.

Morphology Control Strategy of Bimetallic MOF Nanosheets for Upgrading the Sensitivity of Noninvasive Glucose Detection

The precise measurement of glucose level is significant for the health management of the human body. However, the existing sensitive materials and detection methods for glucose are less satisfying for practical applications. Herein, an ultrathin reticular two-dimensional nanosheets array composed of trimesic acid (H₃BTC)-based bimetal metal-organic frameworks (MOFs) and carbon cloth (CC), which is constructed through a morphology control strategy, is reported for glucose sensing. Meanwhile, this nonmoving sweat glucose sensor based on a NiCo-BTC/CC electrode has been successfully prepared by a screen printing method. Benefiting from the regular and ultrathin nanosheets array, the NiCo-BTC/CC electrode has an excellent sensitivity of 2701.29 μA mM^-1 cm^-2, which is about 2.4 times that of its unregulated counterpart (1127.85 μA mM^-1 cm^-2) in the linear range 5-205 μM. In addition, an ultralow detection limit (0.09 μM, S/N = 3) and good selectivity of NiCo-BTC/CC were also obtained. The high sensitivity of the glucose sensor based on NiCo-BTC/CC electrode is 0.174 μA μM^-1 (50-1000 μM). Remarkably, the preciously designed sensor is used to detect glucose concentration in sweat with a noninvasive mode, and the results are basically consistent with those of a commercial glucose device with an invasive mode. This research exhibits potential methodology for the morphology design of bimetallic MOFs nanosheets to achieve a high accuracy rate and noninvasive and timeless measurement of a glucose sensor.

Edge-enriched MoS2 nanosheets modified porous nanosheet-assembled hierarchical In2O3 microflowers for room temperature detection of NO2 with ultrahigh sensitivity and selectivity

Nitrogen dioxide (NO₂) is one of the most hazardous toxic pollutants to human health and the environment. However, deficiencies of low sensitivity and poor selectivity at room temperature (RT) restrain the application of NO₂ sensors. Herein, the edge-enriched MoS₂ nanosheets modified porous nanosheets-assembled three-dimensional (3D) In₂O₃ microflowers have been synthesized to improve the sensitivity and selectivity of NO₂ detection at RT. The results show that the In₂O₃/MoS₂ composite sensor exhibits a response as high as 343.09-5 ppm NO₂, which is 309 and 72.5 times higher than the sensors based on the pristine MoS₂ and In₂O₃. The composite sensor also shows short recovery time (37 s), excellent repeatability and long-term stability. Furthermore, the response of the In₂O₃/MoS₂ sensor to NO₂ is at least 30 times higher than that of other gases, proving the ultrahigh selectivity of the sensor. The outstanding sensing performance of the In₂O₃/MoS₂ sensor can be attributed to the synergistic effect and abundant active sites originating from the p-n heterojunction, exposed edge structures and the designed 2D/3D hybrid structure. The strategy proposed herein is expected to provide a useful reference for the development of high-performance RT NO₂ sensors.

Texturing of nanocoatings for surface acoustic wave-based sensors for volatile organic compounds

An approach for texturing of gas-sensitive nanocoatings by using surface acoustic waves (SAW) is presented in this article. The objective of the work is to enhance the performance of precise SAW-based gas sensors due to the increased specific area of the sensitive nanocoating, induced during its growth and to replace the expensive lithographic techniques for nanopatterning, typically used for this purpose. The technique can be used for tuneable alignment of nanoparticles or nanowires and it is scale-independent. To control the texture of the sensitive nanocoating, a specific electrode topology was used to generate waves with a specific space distribution, which in turn caused assembling of the nanoparticles increasing the adsorption capacity. In this way, a broader dynamic range of 7,000 ppm was achieved (three times extended as compared to the non-textured sensing film), measurement error of 0.6% against 4% for the non-patterned, faster response time in the sub-seconds range (970 ms vs 1.1 s), negligible hysteresis of 10 mV (against >100 mV), and very good sensitivity of 5 µV per ppm, which are in line with the current standards for ethanol sensors. The enhanced sensor parameters were achieved by implementation of conventional patterning technologies without the need for nanolithographic techniques for the texturing the nanocoating. The method is low-cost, and applicable in a variety of sensing structures despite the sensing coating (optical, biological, etc.).

Au Functionalized SnS2 Nanosheets Based Chemiresistive NO2 Sensors

Layered Au/SnS2 nanosheet based chemiresistive-type sensors were successfully prepared by using an in situ chemical reduction method followed by the hydrothermal treatment. SEM and XRD were used to study the microscopic morphology and crystal lattice structure of the synthesis of Au/SnS2 nanomaterials. TEM and XPS characterization were further carried out to verify the formation of the Schottky barrier between SnS2 nanosheets and Au nanoparticles. The as-fabricated Au/SnS2 nanosheet based sensor demonstrated excellent sensing properties to low-concentrations of NO2, and the response of the sensor to 4 ppm NO2 at 120 °C was approximately 3.94, which was 65% higher than that of the pristine SnS2 (2.39)-based sensor. Moreover, compared to that (220 s/520 s) of the pristine SnS2-based sensor, the response/recovery time of the Au/SnS2-based one was significantly improved, reducing to 42 s/127 s, respectively. The sensor presents a favorable long-term stability with a deviation in the response of less than 4% for 40 days, and a brilliant selectivity to several possible interferents such as NH3, acetone, toluene, benzene, methanol, ethanol, and formaldehyde. The Schottky barrier that formed at the interface between the SnS2 nanosheets and Au nanoparticles modulated the conducting channel of the nanocomposites. The “catalysis effect” and “spillover effect” of noble metals jointly improved the sensitivity of the sensor and effectively decreased the response/recovery time.

In Situ TEM Technique Revealing the Deactivation Mechanism of Bimetallic Pd-Ag Nanoparticles in Hydrogen Sensors

Bimetallic Pd-Ag alloy nanoparticles exhibit satisfactory H₂-sensing improvements and show application potential for H₂ sensor construction. However, the long-term stability of the H₂ sensor with Pd-Ag nanoparticles as the catalyst is found to dramatically decrease during operation. Herein, gas-cell in situ transmission electron microscopy (TEM) is used to investigate the failure mechanisms of Pd-Ag nanoparticles under operation conditions. Based on the in situ TEM results, the Pd-Ag nanoparticles have two failure mechanisms: particles coalescence at 300 °C and phase segregation at 500 °C. Guided by the failure mechanisms, the H₂ sensor is comprehensively optimized based on the working temperature and the amount of Pd-Ag alloy nanoparticles. The optimized sensor exhibits satisfactory H₂-sensing properties, and the response decline of the sensor after 1 month is negligible. The revealing of the failure mechanisms with in situ TEM technology provides a valuable route for developing gas sensors with high long-term stability.