Sodium ion battery-type capacitors (SIBatCs) represent an emerging hybrid energy storage technology capable of delivering both high energy and power densities. This study demonstrates the fabrication of quasi-commercial pouch-type SIBatCs based on NaNi1/3Fe1/3Mn1/3O2/activated carbon (NFM/AC) hybrid cathodes and non-presodiated hard carbon anodes. Through systematic evaluation of five commercial activated carbons (ACs), we establish clear structure-property relationships between AC characteristics and SIBatC electrochemical performance. Vapor-activated ACs outperform alkali-activated counterparts due to their well-developed mesoporous structure (3-14 nm), balanced specific surface area (SSA>1600 m(2) g(-1)), high structural disorder (I-D/I-G > 1.1), and superior thermal stability (>700 degrees C). Consequently, vapor-activated AC-3# (SSA: 1659 m(2) g(-1); particle size: 6.6 mu m; I-D/I-G = 1.23; O/C atomic ratio: 6.73) is identified as the optimal candidate. The optimized SIBatC device employing the NFM/AC-3# hybrid cathode achieves energy densities of 161.9 Wh kg(-1) at 41.9 W kg(-1) and 21.2 Wh kg(-1) at 16158.0 W kg(-1). It also retains 53.0 % capacity at 60C and 77.6 % after 3000 cycles (5C), with a robust operation temperature range from -20 degrees C to 60 degrees C. These findings provide crucial design principles for AC in high-performance sodium ion hybrid energy storage systems, emphasizing the importance of vapor activation, mesopore dominance, balanced SSA, and controlled particle properties.

Volatile organic compounds (VOCs), such as formaldehyde (HCHO) and acetone (C3H6O), are ubiquitous air pollutants in industrial and indoor environments and pose serious risks to human health, driving demand for selective, sensitive detection. Metal-organic frameworks (MOFs) are promising sensing nanomaterials due to their structural tunability and modifiable pore chemistry. However, the vast structural diversity of MOFs makes it difficult to identify materials with selective responses toward specific VOCs, and current development still relies heavily on empirical trial-and-error screening. Herein, we integrate density functional theory (DFT) calculations, quartz crystal microbalance (QCM) experiments and complementary spectroscopic characterization to establish a rational design strategy for VOC-selective MOF sensors, using functionalized UiO-66 as a model. DFT analyses quantify adsorption energies, hydrogen-bonding interactions, dipole coupling, and electronic perturbations between functionalized UiO-66 and HCHO or C3H6O. QCM measurements, Fourier-transform infrared (FTIR) and UV-vis spectroscopy verify the theoretical predictions. Our results indicate that UiO-66-NH2 preferentially responds to HCHO, while UiO-66-OH prefers C3H6O. This work shows a direct mechanistic link between the MOF structure and sensing performance, bypassing exhaustive empirical screening and laying a foundation for rational MOF sensor design.

Metal oxide semiconductor-supported noble metal nanoparticles are common sensing materials for gas sensors. However, the large size and their tendency to migrate at high temperatures often lead to inferior sensing sensitivity and stability. Herein, a salt-assistant strategy is developed to prepare fully-exposed Ir clusters on SnO2 nanorods, enabling highly sensitive and stable H2 sensing. By introducing potassium nitrate as a precursor, it was found that the nitrate can induce the Ir species to be exposed on the SnO2 surface in the form of highly-distributed nanoclusters with an average size of less than 1 nm. Meanwhile, the strong interaction between SnO2 and Ir clusters ensures the durability of the catalysts under elevated temperatures (300 degrees C). The final Clu-Ir/SnO2 sensors exhibit excellent H2 sensing performance, featuring a high response value (46 @ 4000 ppm H2), fast response/recovery time (4.6/3.7 s @ 4000 ppm H2), and a low detection limit (as low as 1 ppm). Notably, no significant change in the dispersion state of the Ir metal is observed even after 60 days of continuous use, demonstrating excellent long-term stability. In situ Raman, ex situ X-ray photoelectron spectroscopy (XPS), and H2-temperature-programmed reduction (TPR) results prove that the sensitization mechanism of fully dispersed and exposed Ir clusters involves oxygen capture and activation, H2 adsorption and conversion to H species, and optimization of electron transfer pathways to SnO2. Overall, this study provides valuable insights into the synthesis of fully exposed cluster catalysts capable of stable operation under high temperatures in gas sensing applications. (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)1(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(300 degrees C)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)Clu-Ir/SnO2(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic):(sic)(sic)(sic)(sic)(sic)(sic)(46 @ 4000 ppm H2),(sic)(sic)(sic)(sic)/(sic)(sic)(sic)(sic)(4.6/3.7(sic) @ 4000 ppm H2)(sic)(sic)(sic)(sic)(sic)((sic)(sic)1 ppm).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)60(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic),(sic)(sic)(sic)XPS(sic)H2-TPR(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

The development of highly selective trace ammonia (NH3) detection technology based on metal-organic frameworks (MOFs) is of critical significance for the precise monitoring of ammonia in industrial and agricultural production environments. In this study, a series of UiO-66 materials doped with different metal ions (X-UiO-66, X = nickel, copper, iron, and aluminum) were synthesized. Through comparative analysis, the Ni-UiO-66 based QCM sensor exhibited superior sensing performance for trace NH3 at room temperature: A detection limit as low as 50 ppb, high sensitivity (frequency response of 1766Hz to 25 ppm NH3), fast response/recovery times (10s/13s), as well as good selectivity, long-term stability, and reliable detection capability in high-humidity environments. The doping of Ni2+ creates defects in the framework, increases the specific surface area, and provides more abundant active adsorption sites, thereby significantly enhancing the sensitivity to NH3. Furthermore, adsorption tests, Gaussian simulations, and in-situ infrared spectroscopy revealed a significantly optimized reversible weak chemical adsorption interaction between Ni-UiO-66 and NH3, which endowed the material with enhanced selectivity compared to pristine UiO-66 toward NH3. This work provides a reliable strategy for designing MOF-based sensing materials that combine structural stability and high activity.

Exhaled breath analysis, situated at the intersection of nanomaterial science, analytical chemistry, and clinical diagnostics, is a transformative noninvasive diagnostic technology. However, the ultratrace concentration (ppb-ppm scale) and complex matrix of biomarkers such as nitrogen oxides (NOx) in exhaled breath impose stringent challenges for detection technologies. In this work, we successfully synthesized In2O3-N nanorods with well-defined O-In-N asymmetric active sites via a hydrothermal method and subsequent calcination. The effects of nitrogen doping concentration on the microstructure and gas-sensing properties were systematically investigated, and the optimal doping content was determined. At 80 °C, the In2O3-N sensor exhibits excellent sensing performance toward nitrogen dioxide. Its response reaches 4.5-2 ppm of NO2, approximately 2.2 times that of pristine In2O3. Additionally, it displays excellent selectivity toward NOx (negligible response to non-NOx interfering gases) and good stability (response fluctuation <5% in five cycles). Considering the high humidity in practical detection environments, we further evaluated its humidity resistance. The sensor operates stably over a wide humidity range and possesses strong capability against humidity interference. DFT calculations reveal that the enhanced performances result from two key factors. One is that nitrogen treatment increases the concentration of oxygen vacancies, thereby providing abundant adsorption sites. The other is that in the O-In-N asymmetric sites, electrons transfer from the N atom to the In atom, strengthening the orbital interactions between the In atom in In2O3-N and the N atom in NO2. The In2O3-N-based sensors were further integrated into a portable device for noninvasive pneumonia detection. Clinical tests on 40 exhaled breath samples show that the sensor can effectively distinguish between the two groups of people, with 100% accuracy for pneumonia patients and 80% accuracy for healthy individuals, which is further verified by 3D principal component analysis (PCA) with good separation of sample points. This work not only provides a generalizable strategy for designing high-performance gas sensors via asymmetric active site engineering but also highlights the great potential of In2O3-N sensors in clinical noninvasive diagnosis bridging the gap between nanomaterial design and translational breath analysis.

The surficial inherent properties of TiO2 like exposed facet and crystalline state are vital for their surface reactions. However, efficiently controlling the specific crystal structure and the exposed crystal surface still faces big challenge. Here, the controlled solid phase transition of amorphous TiO2 to crystalline phase with exposed crystal facet (001) is achieved by photo-assisted atomic layer deposition (ALD) Pt process. Significantly, the obtained Pt/TiO2 film via photo-assisted treatment exhibits high sensing performance to NO and HF, and shows a lower optimized working temperature. The enhanced sensing performance is attributed to the metal-support strong interaction under oxidative atmosphere (O-SMSI). The facet effects leading to the unique distribution of charges at the interface combined with the catalytic effects result in the high sensing performance. This work provides a novel phase transition engineering strategy for regulating TiO2 from amorphous to crystalline phase, and the controllable synthesis of high Pt monatomic loading on TiO2 via ALD, which are critical for the accurate synthesis of efficient sensing and catalytic nanomaterials.

Intelligent gas-sensing technology that accurately and stably identifies gas categories in complex atmospheres is critical for protecting public safety and environment. However, competing interactions among different gases on sensing surfaces can trigger interference even poison of sensors. Here, we present a bio-inspired atomic internalization process that produces locally enriched single Pt species, enabling highly selective and interference-resistant gas detection. By engineering Sn/C precursors as homologous receptors, Pt3Sn alloys are two-step redistributed into high-density single Pt species within regionalized SnO2 surface. This structure constitutionally alters the distribution patterns of NO2 molecules and thus delivers accurate NO2 monitoring in multicomponent atmospheres and stable detection for over 550 days, surpassing state-of-the-art commercial devices. Further integrating characteristic-specific sensors into arrays, the resulting device further achieves 100% classification accuracy for single and mixed gases at ultralow cost. Moreover, we demonstrate an autonomous “cruise-monitoring” system by equipping the sensor on a robot to detect and identify NO2 in real time. Our findings thus guide the accurate analysis and interference-resistant detection in complex gas mixtures. Accurate gas sensing remains challenging because conventional semiconductor sensors often struggle with selectivity and interference from complex gas mixtures. Here, the authors use a single-atom catalyst strategy to stabilize isolated Pt atoms on regionalized SnO₂ surfaces, enabling selective and antiinterference NO₂ detection. The resulting sensor operates continuously in air for more than 550 days and achieves high classification accuracy across a library of 37 gases, highlighting the promise of single-atom-engineered sensors for reliable gas monitoring.

Noninvasive disease diagnosis through the exhaled nitric oxide (NO) biomarker is of great significance for the real-time screening of asthma patients. Herein, a high-performance artificial olfactory system (E-nose) based on porous In2O3 nanorods functionalized with Pt, Pd, and PtPd was designed and prepared for the precise recognition of the asthma biomarker NO and the noninvasive diagnosis of asthma. The sensor array demonstrates a limit of detection (LOD) of approximately 1.33 ppb (PtPd/In2O3) for NO and maintains high selectivity. To overcome the prolonged response/recovery times of room-temperature gas sensors and the indistinguishable response values for structurally similar molecules, a novel response transient-aware prototypical network model is proposed. By dynamically extracting transient features from early response stages, the model achieves a high classification accuracy of 94.44% for structurally similar nitrogen oxides (NO, NO2, and N2O). On a clinical dataset comprising 61 participants (42 healthy volunteers and 19 asthma patients), the E-nose system achieved a high accuracy of 93.75% based on the full time-series response stage. Notably, the accuracy of the early-response stage reached 92.85%, validating the feasibility of rapid diagnosis by using early-response segments. These results demonstrate that the artificial olfactory system based on metal-functionalized porous In2O3 nanorods has great potential in the precise and non-invasive diagnosis of asthma. It also offers useful guidance for rapid detection, even when sensors with slow response and recovery times are employed.

Accurately monitoring carcinogenic volatile aromatic hydrocarbons (BTXs) is crucial for assessing air-qualities and danger-classes in specific occasions, However, it remains challenging to conduct highly selective identification of them in complex environments. Here, we have developed a gas-shunting strategy by installing function-reversal ZnO materials into Ir-WO3 supports to diminish interference-gas responses and guide special aromatic hydrocarbons sensing. We find that ZnO materials can serve as reactively sacrificial sites for small-molecule H2S and CO and induce main aromatic hydrocarbons reactants into Ir-WO3 supports. This gas-shunting route guarantees highly-selective aromatic hydrocarbons sensing even in dual/ternary gas mixtures. Through integrating functional-opposite sensors into a system, the final sensing arrays achieve 100% classification accuracy for 10 single gases and 75 multi-compose gases with low training costs. In addition, we also show an autonomic "cruise-detection" system by equipping sensor arrays into robotic dog to accurately identify complex gases. Our findings emphasize sensors designs with selective features and may broaden integrated sensing-system analysis in complex environment.

The volatile organic compounds (VOCs) in exhaled breath have been proven to serve as potential biomarkers for detection of esophageal cancer (EC), providing a novel diagnostic approach. However, it is a great challenge to diagnose the EC accurately due to the low concentration of biomarkers and complexity of exhaled breath. Various nanocoils (NCs) materials were synthesized via atomic layer deposition (ALD). The NCs-based sensors, characterized by the enrichment effect generated through nanostructured confinement, exhibited excellent sensing performance toward mixed aldehyde and ketone gases, achieving an experimentally measured response value of 1.22@1 ppb from the SnNiSnNCs sensor within the array. These sensors also maintained a notable response to trace-level multicomponent gas mixtures, even under high-humidity conditions. Meanwhile, NCsbased sensors exhibited significant differences in sensing performance such as sensitivity, selectivity, and response/recovery time for different target gases. Subsequently, the integrated CNN-LSTM-Attention model was trained and evaluated utilizing a dataset consisting of 27 distinct low-concentration gases, leading to a high accuracy (98.05 %) in gas classification. Then, an intelligent olfactory system (E-nose) with NCs based sensors array and the integrated CNN-LSTM-Attention model showed high accuracy (97.50%) in distinguishing the EC patients and healthy individuals. This E-nose with an excellent gas-sensing performance through enrichment of confined nanostructure and the integrated model algorithms provides a feasible and non-invasive strategy for efficient exhaled breath disease diagnosis, which could be extended to the diagnosis of other diseases.

Gas sensors are efficient for environmental pollution monitoring. Studies have shown that heterojunction engineering is highly promising for gas sensing by modulating the interfacial electric field (IEF), yet its regulation mechanism on the electronic structure of surface-active sites remains insufficiently understood. Herein, we construct a tailored IEF in alpha-Fe2O3@Co3O4 heterojunctions to upshift Co3 + sites' d-band center, optimizing target gas adsorption. The material exhibits an ultrahigh formaldehyde response (26.5 to 1 ppm), rapid response-recovery, and 100 ppb detection capability. In situ/ex situ characterizations and theoretical calculations confirm the IEF enhances Co3 + sites' adsorption by increasing antibonding orbital occupancy. As a core thermodynamic parameter characterizing the energy variation of the system, enthalpy holds great significance in this work: its enthalpy change can quantitatively reflect the energy variation in the adsorption process, provide thermodynamic evidence for the upshift of the d-band center and the increased occupancy of antibonding orbitals, and clarify the spontaneous direction and intensity of the reaction as well as the intrinsic thermodynamic mechanism underlying the enhanced adsorption capability induced by the IEF. Integrating with a MEMS array and wireless device enables real-time monitoring and cloud transmission, laying a foundation for indoor environmental health monitoring.

The severe impact of humidity on low-temperature sensing performance has long been an urgent issue to be addressed in the field of semiconductor gas sensors. In many scenarios, such as breath analysis, sewers, swamps and mines, H2S coexists with a large amount of water vapor, making it particularly necessary to improve its low-temperature moisture resistance. In this paper, A HEA was fabricated and employed to improve the low-temperature moisture resistance of SnO2-based H2S sensors. The results show that 1.5 wt% HEA modified SnO2 exhibits the best sensitization performance toward H2S gas sensor, and excellent moisture resistance at low temperatures. At high relative humidity (RH = 80%), a response of 15 was maintained with no decline over the 7-day test period. At the same time, it can also enhance the H2S (0.5 ppm) response on SnO2 from 1.2 to 22, lower the response time from 30 s to 4 s, the recovery time from 140 s to 101 s, and decrease the limit of detection (LOD) down to 41 ppb at 70 °C. Theoretical calculations show that HEA can enhance the competitive adsorption of oxygen to water, thereby increasing the concentration of reactive oxygen species (ROS). Additionally, the electron transfer from HEA to SnO2 can jointly regulate the energy-to-structure and carrier concentration of SnO2, promoting the adsorption of oxygen and the reaction with H2S. This study offers a new strategy for improving the low-temperature performance of gas sensors under high-humidity environments.

The safe utilization of hydrogen energy urgently demands hydrogen sensors with high sensitivity and rapid response. Herein, we propose a vacancy-assisted single-atom synergistic strategy to significantly enhance the hydrogen sensing performances by simultaneously constructing palladium single atoms (Pd-SAs) and sulfur vacancies (Vs) in MoS2 surfaces. It is found that Pd single atoms can optimize the electronic structure of in-plane S atoms through Pd-S bonding while sulfur vacancies can enhance the kinetic adsorption of hydrogen and form atomic-scale Pd-S-Mo bond to modulate the electronic states of S. In-suit Raman spectroscopy experiments demonstrate that activated sulfur surfaces undergo more intense electron transfer with H2 molecules. Additionally, H2 adsorption and desorption kinetic tests and density functional theory (DFT) calculations reveal that Pd single-atom and sulfur vacancy-rich MoS2 (Pd1-MoS2-Vs) exhibits enhanced hydrogen molecule adsorption capacity, greater adsorption energy, and consequently a higher hydrogen response value. The final Pd1-MoS2-Vs sensor owns an outstanding response (2.32/400 ppm) to H2 at a low working temperature (120 degrees C), extremely low detection limit (5 ppm) and excellent selectivity and humidity stability. Our work offers new perspectives for the development of hydrogen sensors.

Nitrogen oxide (NOx) necessitates low-concentration detection at elevated temperatures due to its toxicity for both human health and sensing materials. This work demonstrates the use of Ni-doped Co3O4 frameworks (NCO) as high-performance sensing materials, that are derived from Ni-ZIF-67 via thermal annealing. Among that, the NCO-2 sample, featuring a hierarchical hollow structure with a specific surface area of 94.89 m2/g, enables sensitive detection of low-concentration NOx, especially 500 ppb NO2 at 150 degrees C with a high response value of Ra/ Rg-1 = 5.35 and high selectivity (SNO2/SCO=26.75). Characterization techniques and DFT calculations combined to confirm that Ni2+ substitute for Co2+ in tetrahedral sites of the Co3O4 is a strong adsorption sites for NO2 molecules with a high adsorption enthalpy of-3.04 eV and + 0.44 e transfer. Ex situ XPS analysis further elucidates NO2 poisoning mechanisms by identifying the formation of stable NO3-/NO2-species on the sensor surface at high concentrations, and provided corresponding solutions. To bridge laboratory research and practical application, a portable NO2 detector was developed by integrating an NCO-2 sensor array with smartphone connectivity. This device enables real-time monitoring of environmental NO2 pollution. Collectively, this study presents an integrated system that advances NO2 sensor research by combining material design, mechanistic insight, and prototype development.

ABSTRACT As an effective sensitizer for chemiresistive hydrogen (H 2 ) sensors, the practical application of Palladium (Pd) is limited by the Sabatier principle, where intrinsically strong Pd─H binding leads to sluggish desorption kinetics and prolonged response and recovery time. A high‐entropy alloying strategy was proposed to tailor the local coordination and electronic structure of Pd active sites and weaken the Pd─H binding. Pd x (FeCoNiCu) 1− x ( x = 0.05–0.35)high‐entropy alloys (HEAs) were synthesized as sensitizers for SnO 2 to improve its H 2 sensing reactivity, especially its response and recovery rate. Pd 0.2 (FeCoNiCu) 0.8 ‐SnO 2 sensor exhibits short response and recovery time (0.6 s/2.0 s), a high response of 18.8 toward 100 ppm H 2 (4.06 times higher than Pd‐SnO 2 ), a practical detection limit of 1 ppm and a long‐term stability (>90% retention over 50 days). The working window of the sensor is also wider, which exhibits a linear response in both low (20–120 ppm) and high (4000–20 000 ppm) H 2 concentration ranges. Experimental analysis and theoretical calculation attribute this performance to the downshift of the Pd d ‐band center (from −1.84 to −2.57 eV). The electronic modulation alleviates the strong binding of hydrogen intermediates, thus leading to ultrafast response and recovery without compromising sensitivity.

Hydrogen sulfide (H2S) is a harmful substance existing widely, it exerts significant impacts on both ecosystems and human beings, requiring timely detection. A ZnFe2O4@ZnO (ZFO@ZnO) p-n heterojunction was synthesized by using MIL-88A(Fe) as a precursor. p-ZnFe2O4 and n-ZnO serve as the core and shell layer, respectively. The energy band structure is reconstructed, resulting in formation of an internal built-in electric field between p and n region, reducing the bandgap width further inducing a large number of oxygen vacancy at the interface of heterojunctions. The existence of the p-n heterojunction and the internal built-in electric field was directly confirmed by HRTEM image, I-V curve, and UV-Vis DRS data. Gas sensing tests revealed that this sample exhibits ultrahigh performance toward H2S, with a response of 58.9-1 ppm. It also features ultra-fast response and recovery characteristics, enabling real-time detection of low-concentration H2S (100 ppb). Ex-situ XPS and EPR of the sample treated with HAS was employed to reveal the H2S sensing mechanism. It is found a small amount of ZnS and S0 are formed during the sensing process, and these two substances can be removed by heating them in air, thereby achieving long-term H2S sensing stability. In addition, we verified the practical application value of this gas sensor in terms of food spoilage. After a continuous experiment, the device can well distinguish spoiled eggs and fresh eggs. In summary, this work has not only been thoroughly investigated at the experimental level, but also achieved the transition from laboratory to application.

Enhancing the gas-sensing properties of metal oxide semiconductors using noble metals' electronic and chemical sensitization functions is a common approach to develop high-performance gas sensors. However, the high cost and scarcity of noble metals pose challenges to sustainability. In this study, a non-noble metal MnFeCoNiCu high-entropy alloy (HEA) was designed as an alternative to noble metals to enhance the sensitivity of SnO2 and enable efficient, stable, and rapid detection of acetone (C3H6O). The MnFeCoNiCu HEA-loaded SnO2 demonstrated improved performance in C3H6O detection, including high selectivity (κ > 3), a high sensitivity (Ra/Rg = 4.17 at 0.5 ppm), a low detection limit (30 ppb), fast response and recovery time (4.6 s/5 s), long-term stability (over 50 days), and resistance to humidity (stable at 90% RH). The enhanced performance of the HEA is attributed to the fact that it possesses more valence electrons and the electrons can transfer and redistribute among different atoms, which leads to an increase in active oxygen species and catalytic sites, promoting electron sensitization. This study provides insights into designing and developing a highly catalytic, non-noble metal HEA for gas-sensing applications.

Cobalt-based spinel oxides are emerging as low-cost and selective materials for gas sensing, though their performance is still unsatisfactory. In this study, we developed a refined method to produce (Cu0.2Co0.8)Co2O4 frameworks derived from Cu-doped ZIF-67. This unique synthesis method imparts a distinctive morphology to the (Cu0.2Co0.8)Co2O4, featuring a high density of surface oxygen vacancies and doped Cu2+ ions bring stronger interaction between H2S molecules and the (Cu0.2Co0.8)Co2O4 coating, resulting in exceptional H2S gas sensing performance, including a high response value (Delta R/Ra = 5.11-500 ppb H2S), rapid response-recovery times (tau res = 3.6 s, tau res = 10.8 s) and an ultra-low detection limit (50 ppb). These results demonstrate the promising potential of this material for H2S gas detection applications. Ex situ XPS characterization reveals the gas sensing reaction mechanism, while density functional theory calculations confirm that the presence of Cu2+ significantly reduces the H2S adsorption enthalpy, thereby enhancing the overall gas sensing performance. This work not only introduces an approach to provide a better H2S gas sensor, but also paves new pathways for advanced inorganic synthesis methods for metal oxide catalysts.

Amorphous noble metals often display excellent sensitization due to their unsaturated atomic coordination and abundant active sites on the surface. In this work, amorphous palladium-ruthenium bimetallic nanoparticles were successfully prepared by lithium doping and incorporated into MOF-303 by using a confinement strategy. Compared with crystalline c-PdRuO x @MOF-303, the low-humidity sensor constructed with amorphous a-PdRuO x @MOF-303 exhibits higher response values (3600 Hz to 3.39% RH), shorter response/recovery time (9/7 s), low-humidity hysteresis (0.16% RH) and excellent stability. Meanwhile, the a-PdRuO x @MOF-303 sensor has been further explored to achieve continuous monitoring of human breathing, cough, and finger humidity, providing broad application prospects for amorphous materials in wearable medical devices and noncontact human-machine interactions. Additionally, the sensitive mechanism was explored by GCMC methods. The simulation results demonstrate that introducing a-PdRuO x into the pores of MOF-303 leads to significant enhancement in adsorption properties. This improvement is not only due tothe increase of active sites provided by a-PdRuO x but also the substantial rise in adsorption energy for the hydrophilic pocket of MOF-303. The adsorption energy increases from -25.70 to -31.56 kJ/mol, highlighting that the abundant active sites of the a-PdRuO x work in synergy with the hydrophilic pocket of MOF-303. This synergy enables the adsorption and activation of more water molecules, effectively enhancing the overall adsorption capacity and performance of the MOF-303.