Vapor Concentration Research Articles

Comparing the Two Methods of Ion Chromatography and Titration in Evaluating the Concentration of Sulfuric Acid Mist and Vapor in the General Air of the Electrolysis Unit of the Copper Production Industry

Comparing the Two Methods of Ion Chromatography and Titration in Evaluating the Concentration of Sulfuric Acid Mist and Vapor in the General Air of the Electrolysis Unit of the Copper Production Industry

Influence of water vapor concentration on photoacoustic spectroscopy‐based characteristic gas analysis of transformer faults

AbstractThe water vapor in the ambient air affects the accuracy of the photoacoustic (PA) dissolved gas analysis system for transformer health monitoring. A laser PA system was evaluated by dry and humidified standard gases to study the influence of water vapor concentration on PA gas detection. Theoretical analysis was conducted on the effect of gas molecule relaxation on PA signal detection. A high‐frequency resonant PA cell and a low‐frequency nonresonant PA cell were used to detect acetylene (C2H2) and carbon monoxide (CO), respectively. The experimental results show that the PA signal of humidified CO is about 12 times higher than PA signal of dry gas for the resonant PA detection system, respectively. In addition, as the frequency is increased from 30 to 980 Hz, the PA signals of humidified and dry CO attenuate by 1.5 and 6.9 times, respectively.

CCN Activation and Droplet Growth in Pi Chamber Simulations with Lagrangian Particle–Based Microphysics

Abstract Numerical simulations of turbulent moist Rayleigh–Bénard convection driving CCN activation and droplet growth in the laboratory Pi chamber are discussed. Supersaturation fluctuations come from isobaric mixing of warm and humid air rising from the lower boundary with colder air featuring lower water vapor concentrations descending from the upper boundary. Lagrangian particle–based microphysics is used to represent the growth of haze CCN and cloud droplets with kinetic, solute, and surface tension effects included. Dry CCN spectra in the range between 2- and 200-nm radii from field observations are considered. Increasing the total CCN concentration from pristine to polluted conditions results in an increase in the droplet concentration and reduction in the mean droplet radius and spectral width. These are in agreement with Pi chamber observations and numerical simulations, as well as with numerous past studies of CCN cloud-base activation in natural clouds. The key result is that a relatively small fraction of the available CCN is activated in the Pi chamber fluctuating supersaturations, from about a half in the pristine case to only a 10th in the polluted case. The activation fraction as a function of the dry CCN radius is similar in all simulations, close to zero at the CCN small end, increasing to a maximum at CCN radius around 50 nm, and decreasing to close to zero at the large CCN end. This is explained as too small supersaturations to activate small CCN as in natural clouds and insufficient time to allow large CCN reaching the critical radius. Significance Statement Impact of turbulence on the formation and growth of cloud droplets is an important cloud physics problem. Laboratory experiments in the Michigan Technological University cloud chamber provide key insights into this problem. Numerical simulations of cloud chamber processes discussed in this paper complement laboratory experiments by providing insights difficult or impossible to obtain in the laboratory. The study contrasts the formation and growth of cloud droplets in the laboratory cloud chamber with processes taking place in natural clouds. The differences documented in this paper pose questions concerning the impact of turbulence on the formation and growth of cloud droplets as a result of interactions of clouds with their environment.

Current-Voltage (i-V) characteristics of electrolyte-supported (NiO-YSZ/NiO-SDC/ScSZ/LSCF-GDC/LSCF) solid oxide electrolysis cell during CO2/H2O co-electrolysis

Solid oxide electrolysis cells (SOECs) stabilize CO2 emissions by converting CO2/H2O into synfuel. Current-Voltage (i-V) characteristics of an electrolyte-supported button cell (NiO-YSZ/NiO-SDC/ScSZ/LSCF-GDC/LSCF) were measured as a function of temperature, water vapor concentration, and CO2 gas concentrations. The cell microstructure was characterized by the Field Emission Scanning Electron Microscope (FE-SEM). FE-SEM micrographs depict that the electrolyte layer is relatively dense, and porous fuel and air electrode layers are well adhered to the electrolyte. The i-V curves were obtained at a scan rate of 0.02 Vs−1 from 0.3 to 1.5 V. Electrolysis current density increases as the temperature increases. SOEC performance increases, but SOFC performance decreases with increased water vapor concentration. Electrolysis current densities decrease as the CO2 concentration increases. The i-V characteristics show only ohmic polarization under fuel-lean and fuel-rich conditions. At optimal conditions, current density values at 800 °C/1.5 V are -174, -187, and -195 mA cm−2 for 5 %H2O, 30 %CO2, and 30 %CO2/5 %H2O co-electrolysis. At 800 °C, open-circuit voltage (OCV) values for H2O, CO2, and co-electrolysis are 0.906, 0.891, and 0.885 V, respectively. The electrolysis area-specific resistances (ASRs) give information on the reduction of CO2 or H2O, forming CO or H2, respectively. At optimal conditions, ASR values are 3.43, 3.29, and 3.18 Ω cm2 for H2O, CO2, and co-electrolysis, respectively. Co-electrolysis has a lower ASR value than pure H2O and CO2 electrolysis, indicating that H2O and CO2 are involved in the electrochemical processes.

Heat and moisture transfer through skin-clothing microclimate

The microclimate between clothing and human skin plays an important role in the heat and moisture exchange between body and ambient environment, which is essential to the thermo-physiological comfort. Despite extensive research on microclimate heat transfer, the sweating process accompanying heat transfer has often been neglected, and the investigation of transport mechanisms is limited. In this study, the heat and moisture transfer from skin to environment was experimentally and numerically simulated with focus on factors such as microclimate thickness (0 mm ∼ 40 mm), tilt angle (0° ∼ 90°), and airflow direction (parallel and normal to the fabric surface). The skin was represented by a surface with uniform temperature in experiments and numerical simulations, and the fabric was modeled as an air-permeable porous medium in the numerical simulations. The experimentally validated numerical model provided detailed distributions of temperature, vapor concentration, and airflow patterns in the microclimate for both dry and wet skins. The airflow of natural convection featured multiple circulation cells, and their circulation times were calculated and then related to the microclimate transport performance. It was found that natural convection dominates the heat and moisture transfer in thicker microclimates. It was also found that normal airflow was more effective in facilitating the heat and moisture transfer as compared to parallel airflow. The results are useful for developing high-performance clothing optimized for thermal regulation and moisture management, improving comfort and safety in different conditions.

Carbon nanotube interweaved Fe7Se8 nanosheet/nanorod hybrids on expanded graphite for high-performance sodium storage

The construction of nano-micro scale hybrid structures by carbon materials is an effective strategy to address the issues of metal chalcogenides when used as anodes of sodium-ion batteries. Herein, we develop a carbon nanotube (CNT)-interweaved Fe7Se8/expanded graphite (EG) composite by means of a facile one-step gas-phase pyrolysis route with ferrocene, selenium and EG as the starting materials. The ex-situ monitoring of the pyrolysis process indicates that the selenium as a promoter facilitates the formation of CNTs and the carbon coated Fe7Se8 nanosheet/nanorod mixture. A competing reaction between CNT growth and the evolution of Fe7Se8 nanostructures occurs, which could be dominated by the concentration of selenium vapor. By optimizing the feeding ratio and the pyrolysis condition, the nanocomponents are homogeneously deposited on the surface of the EG matrix to realize a well-developed nano-micro hybrid configuration. The constructed three-dimensional conductive network, rich mesopores and high specific surface area (107.1 m2 g−1) contribute to substantially enhanced sodium-storage performance in ester electrolyte. Remarkably, the optimized composite electrode exhibits high reversible capacity retention of 97.5 % after 1000 cycles at 1.0 A g−1 and improved rate performance of 325 mAh g−1 at 2.0 A g−1. This study provides new avenues to develop high-performance metal chalcogenide electrodes for electrochemical energy storage.

Exploring Microwave Reconfigurable Intelligent Surface for Wireless VOC Detection: A Comparative Study of Porous and Solid PDMS Interfaces

AbstractMicrowave gas monitoring with a low‐profile design and enhanced selectivity remains a persistent challenge. This study introduces an innovative approach employing a real‐time wireless reconfigurable intelligent surface (RIS) for comparative investigation of the interaction of two distinct polydimethylsiloxane (PDMS) interfaces, i.e., solid and porous, with acetone gas molecules. The developed PDMS‐coated microwave RIS detects varying concentrations of acetone vapor by wirelessly monitoring variations in the resonant characteristics of the resonating RIS beneath the sensitive interface. This PDMS‐coated microwave RIS is validated through exposure to incremental (15–75) parts per thousand (ppt) acetone concentrations and demonstrated a sensitivity of ≈4.4 MHz/ppt and ≈4.3 MHz/ppt of acetone for solid and porous PDMS, respectively. Integrating PDMS and microwave‐based RIS systems provides a sensitive tool for tracking the interaction of acetone gas and PDMS and demonstrates this system's capability for sensitive gas detection. This study introduces a unique development in the wireless detection of VOCs and presents a compact and passive approach with enhanced sensitivity, making it suitable for monitoring the interaction of polymers and hazardous VOCs. This technology is particularly suited for use in challenging and hard‐to‐reach environments.

Estimation of errors of the spectral method for measuring the concentration of water vapor and moisture reserves in the surface layer of the Earth’s atmosphere

A method for passive measurements of water vapor concentration in the atmosphere in the presence of solar radiation has been proposed and tested. The location of the measurements is the northeast of the Moscow region. When processing the results of measurements carried out on a single water absorption line, a coincidence of experimental data and data obtained from direct meteorological measurements with an error of no more than ~7.5 % was revealed. It was also found that on the water absorption line in the region of 1653 nm, the interfering factor is the nearby methane absorption line, which introduces a systematic error in the measurement results, and the results turn out to be underestimated. A possible reason is that the absorption cross section of methane molecules is ~4 orders of magnitude larger than that of water vapor molecules and light radiation is absorbed to a greater extent by methane, reducing the fraction of absorption of water vapor at a wavelength close to the methane absorption line. Compensatory corrections have been introduced to determine the concentration and moisture content in the atmospheric column with an accuracy of several percent at this wavelength. The proposed technique allows both long-term monitoring of concentration and moisture content in the atmosphere and obtaining operational information in real time. The results of the measurements performed are, on average, consistent with the results of measurements obtained using radiometers operating in the ultrahigh frequency range.

Thickness-dependent morphological, structural, and optical properties of cobalt ferrite films

ABSTRACT A facile and prudent approach has been developed to deposit cobalt ferrite (CoFe2O4) films on the surface of the precursor solution by purging ammonia vapors over it. The vigorous technique to control the thickness of the film attributes spectacular characteristics to this approach. The study of CoFe2O4 films has been carried out by using FE-SEM, AFM, XRD, and UV-Visible spectroscopy. FE-SEM micrographs confirm the formation of the thin films composed of nanoparticles. The AFM micrographs indicate an increase in the root mean square roughness value with purged NH3 concentration due to the aggregation of nanoparticles. The observed XRD spectra show a cubic spinel structure of CoFe2O4 films with an increase in crystallite size in the range of 20–45 nm on increasing the NH3 concentration. UV – Visible spectroscopic investigations show a decrease in the band gap energy from 2.84 to 2.37 eV on account of the increased concentration of NH3 vapors.

Flow Simulation-Based Methodology for Reducing The Risk of Fuel Fire In An Aircraft’s Fuel System Enclosure

ABSTRACT This study applies advanced computational fluid dynamics (CFD) simulations to enhance the safety of an aircraft’s fuel system by striving to minimize the risk of on-board fire hazards. Employing a detailed flow simulation model, this research assesses the efficacy of newly designed measures within a fuel system, designed for a modified radial engine on a test-bed AN 2 airplane. The model simulates internal airflow, droplet particle flow, the formation of Eulerian Wall Film, and the vaporization process from the fuel film within the enclosure of the aircraft’s equipment bay. By exploring both the original and modified geometries of this fuel system enclosure, the simulations provide insights into the flowpaths of leaking fuel, the spatial and temporal distribution of fuel vapor concentrations, and the overall effectiveness of design modifications aimed at rapid removal of hazardous substances. Structural improvements, including the addition of strategic ventilation inlets and outlets, are proposed based on the simulation results to ensure rapid dispersion of vapors and minimal residual fuel, effectively reducing the potential for vapor ignition. This study thus underscores the potential of precise CFD modelling in identifying risks and developing robust fire hazard mitigation strategies in aviation fuel systems.

Experimental investigation on the high-temperature corrosion of 12Cr1MoVG boiler steel in waste-to-energy plants: Effects of superheater operating temperature and moisture

Waste-to-energy (WTE) technology via municipal solid waste incineration (MSWI) have developed very rapidly with the advantages of achievement on waste disposal and energy conversion. This technology is developing towards higher capacity and efficiency. Therefore, the operation parameters of WTE boilers must be improved. However, higher steam parameters means higher surface temperature of exchange tube in superheaters and reheaters in WTE boilers, resulting higher risk of engineering failure due to high-temperature corrosion. Additionally, the incineration of MSW releases flue gas with a high content of corrosive species and water vapor, which can cause severe high-temperature corrosion. This experimental investigation details the effect of surface temperature and water vapor concentration on the high-temperature corrosion behavior of 12Cr1MoVG boiler steel under an atmosphere mimicking MSWI. The corrosion test environment consists of high temperature, ash deposit and simulated flue gas of waste incineration according to a real WTE boiler. The experiment was conducted using a two-zone bench-scale tube furnace with a gas temperature of 600℃ and the sample temperatures of 380℃, 430℃, and 480℃. For the investigation of water vapor concentration effect, 18 % vol and 23 % vol were set up in this study. After 240 hours of exposure, the corrosion weight curves illustrated that the corrosion kinetics was highly dependent on the surface temperature of corrosion samples. Furthermore, an increase in water vapor concentration exacerbated the high-temperature corrosion. XRD analysis identified the corrosion products as metal chlorides and metal oxides. Cross-sectional SEM images and EDS analysis revealed that an increase in water vapor accelerated the corrosion rate of the steel samples due to chromium dilution behavior.

Exact Solution for Water Evaporation During CO2 Injection

AbstractThe objective of this study is to develop an analytical model for 1D gas‐water flow with evaporation of water into the mobile gas phase. The evaporation rate is proportional to the fluid‐fluid interfacial area, which is a function of the water saturation. Introduction of saturation‐dependent potential allows reducing the 2 × 2 non‐linear system of PDEs to one hyperbolic equation. The saturation distribution is obtained by non‐linear method of characteristics. The first integral allows for explicit expression of the vapor concentration versus saturation. It was shown that typical properties of rock‐CO2‐water system, the evaporation time has order of magnitude of millions of pore volumes injected. Close match was observed between a series of three corefloods and the analytical model, and the tuned model coefficients belong to their common intervals. This validates the developed model for 1D gas‐water flow with water evaporation into the injected gas.

Entomological assessment of hessian fabric transfluthrin vapour emanators for protecting against outdoor-biting Aedes aegypti in coastal Tanzania.

A low technology emanator device for slowly releasing vapour of the volatile pyrethroid transfluthrin was recently developed in Tanzania that provides robust protection against night biting Anopheles and Culex vectors of malaria and filariasis for several months. Here these same emanator devices were assessed in Dar es Salaam city, as a means of protection against outdoor-biting Aedes (Stegomia) aegypti, the most important vector of human arboviruses worldwide, in parallel with similar studies in Haiti and Brazil. A series of entomological experiments were conducted under field and semi-field conditions, to evaluate whether transfluthrin emanators protect against wild Ae. aegypti, and also compare the transfluthrin responsiveness of Ae. aegypti originating from wild-caught eggs to established pyrethroid-susceptible Ae. aegypti and Anopheles gambiae colonies. Preliminary measurements of transfluthrin vapour concentration in air samples collected near treated emanators were conducted by gas chromatography-mass spectrometry. Two full field experiments with four different emanator designs and three different transfluthrin formulations consistently indicated negligible reduction of human landing rates by wild Ae. aegypti. Under semi-field conditions in large cages, 50 to 60% reductions of landing rates were observed, regardless of which transfluthrin dose, capture method, emanator placement position, or source of mosquitoes (mildly pyrethroid resistant wild caught Ae. aegypti or pyrethroid-susceptible colonies of Ae. aegypti and An. gambiae) was used. Air samples collected immediately downwind from an emanator treated with the highest transfluthrin dose (15g), contained 12 to 19 μg/m3 transfluthrin vapour. It appears unlikely that the moderate levels of pyrethroid resistance observed in wild Ae. aegypti can explain the modest-to-undetectable levels of protection exhibited. While potential inhalation exposure could be of concern for the highest (15g) dose evaluated, 3g of transfluthrin appears sufficient to achieve the modest levels of protection that were demonstrated entomologically. While the generally low levels of protection against Aedes reported here from Tanzania, and from similar entomological studies in Haiti and Brazil, are discouraging, complementary social science studies in Haiti and Brazil suggest end-users perceive valuable levels of protection against mosquitoes. It therefore remains unclear whether transfluthrin emanators have potential for protecting against Aedes vectors of important human arboviruses.

Monitoring of Sulfur Mustard (HD) Vapor in the Presence of Absorptive Building Materials.

In the event of an accidental or intentional release of a chemical warfare agent (CWA), environmental samples must be collected and analyzed to assess the level of the contamination. Equally important is an understanding of the fate and transport of a CWA in the presence of porous materials, which may impact the ability to collect environmental samples. Air monitoring techniques may be used to rule in/out the presence of a CWA. Here, relationships between the CWA sulfur mustard (HD) surface contamination levels and the associated HD vapor concentration were investigated. Results indicate that absorption of HD into vinyl, concrete, and sealed concrete followed by slow diffusion out of these materials significantly prolonged the presence of HD vapor concentrations. The extracted material recovery data suggest that positive correlations can be established between residual material contamination and vapor concentration but also that surface wiping alone would fail to detect absorbed HD.

Impact of air supply cessation time on thermal characteristics in coal mine dead-end roadway fires: An experimental study

Following a fire incident in a coal mine dead-end roadway, shutting down the local ventilator can influence fire progression. This study delves into the impact of local ventilator shutdown time (i.e. air supply cessation time) on fire source combustion dynamics through small-scale experiments. Results indicate that the sudden cessation of air supply will prompt ghosting flame and even fire self-extinguishing. The ghosting flame emerges due to the uneven distribution of fuel vapor and oxygen concentrations, its moving direction is related to ventilation conditions and fire source combustion mode. And the burning time of the fire source after air supply cessation diminishes with increasing air supply cessation time and pool size but increases with higher ventilation velocities. Additionally, sudden cessation of air supply decreases smoke oxygen content and significantly elevates CO levels, particularly impacting ventilation-controlled fires. Moreover, this interruption leads to a substantial rise in smoke temperature, heightening fire risk. Thus, prudent closure of the local ventilator in dead-end roadway fires is recommended, particularly in scenarios of inadequate ventilation and prolonged combustion. These findings offer fresh insights into dead-end roadway fire behavior and furnish valuable guidance for firefighting and rescue operations in similar structures.

VOF based model of numerical simulation for single aluminum droplet evaporation and combustion

ABSTRACT This study investigates the combustion of a single aluminum droplet in a high-temperature convective setting, focusing on the interplay between the environment and droplet evaporation combustion. Using the VOF numerical method, a two-dimensional multiphase flow combustion model for micron-sized aluminum droplets is developed. Experimental validation compares predicted droplet diameter with experimental data. The combustion behavior of aluminum droplets in high-temperature convective environments is analyzed, emphasizing gas-phase combustion during stable stages. Parametric variations in flow velocity and oxygen concentration reveal the formation of vortices around the droplet, influencing aluminum vapor accumulation and evaporation rates. Combustion primarily occurs at the droplet’s windward side, with reaction rates decreasing downstream. Increasing gas velocity from 1.5 m/s to 3 m/s thins the aluminum vapor concentration boundary layer, boosting combustion rates by 35%. Elevating oxygen concentration from 20% to 50% brings the flame closer to the droplet, accelerating combustion rates by 2.7 times, suggesting oxygen concentration’s role in reaction acceleration and combustion duration reduction. This research offers insights for simulating aluminum droplets in propellant applications.

Naturally Bred Korean Silkworm Cocoon Showing Strong Green Fluorescence and Its Textile-Based Environmental Sensing Applications

ABSTRACT Mulberry silkworms have provided many valuable byproducts to humans for 5,000 years. However, numerous possibilities for their utilization still exist owing to the countless varieties of silkworms. Here, we report the application of Yeonnokjam silk (pistachio silk, PS), one of the characteristic silk varieties in Korea, as a smart fabric environmental sensor. Unlike the previously reported extrinsically modified silk varieties, this new silk textile emits fluorescence under external stimuli. PS cocoons were exposed to different concentrations of HCl vapors. Due to the large surface-to-volume ratio of the cocoon textile, a very low concentration (5 ppm) of HCl vapor can be detected by reading the decrease in the fluorescence intensity. At a lethal concentration (3000 ppm), an instantaneous fluorescence response is obtained. Additionally, the fluorescent pigment in PS can respond to temperature and can be extracted using ethanol, indicating that PS exhibits temperature and ethanol-sensing capabilities. The findings of this study prove that natural PS can be used in bio-optical applications.

Advanced Nanostructured All‐Waterborne Thiol‐Ene/Reduced Graphene Oxide Humidity Sensors with Outstanding Selectivity

AbstractThe current‐state of polymer‐based humidity sensors faces numerous limitations, including energy‐costly synthesis, low sensitivity, and slow response times. This study presents innovative approach to overcome these challenges, based on a robust all‐water‐borne in situ miniemulsion polymerization. The use of water throughout the entire process mitigates the negative environmental impact. Thiol‐ene polymers reinforced with reduced graphene oxide (rGO) with concentrations ranging from 0.2–1.0 wt% are selected to fabricate these chemoresistive sensors. The selected thiol‐enes present high hydrophobicity and a semicrystalline nature, suggesting resistance to early delamination even under prolonged exposure to humidity. Incorporating rGO not only imparts electrical conductivity but also enhances mechanical and water resistance of the composite films. The 0.6% rGO composite exhibits optimal resistance for humidity sensing, demonstrating rapid and consistent responses across three exposure cycles to water vapor concentrations ranging 800–5000 ppm. Moreover, the sensor exhibits remarkable selectivity toward water vapors over these of toluene, propanol, and 4‐methyl‐2‐pentanol, attributed to the high surface hydrophilicity and inherent porosity of the waterborne film, and network structuring of rGO platelets within the matrix. In summary, this study pioneers a novel approach to polymer‐based humidity sensing, addressing key limitations while offering enhanced sensitivity, rapid response times, and superior selectivity.

A kinetic partitioning method for simulating the condensation mass flux of organic vapors in a wide volatility range

Organic aerosols are ubiquitous, playing important roles in various atmospheric physicochemical processes such as the formation of cloud droplets and haze. Condensation of organic vapors, as a net effect of association with particles and dissociation from the condensed phase, is a fundamental process that drives the formation of organic aerosols. Kinetic models are often used to simulate the condensation fluxes of low-volatility organic vapors and aerosol growth. However, the widely used kinetic growth models usually calculate the evaporation of a certain species based on previous particulate compositions, without including the co-condensation of other species. Here we present a new kinetic partitioning method for calculating the condensation fluxes of organic vapors in a wide volatility range with low computational cost. In this method, the organic vapors are assumed to be in a quasi-steady state, but never reach real association-dissociation equilibrium during the simultaneous condensation of multiple species. We show a good consistency between the kinetic partitioning method and kinetic models in simulating particle mass fractions and condensation fluxes. Under relevant atmospheric conditions, we reveal that the kinetic partitioning method also reproduce the trend that low-volatility species are almost non-volatile while volatile organic compounds almost reach association-dissociation equilibrium, while there is a transition regime between them. This transition regime varies with atmospheric conditions, such as temperature and vapor concentrations. Compared with previous studies combining kinetic growth methods with equilibrium partitioning theories to simplify the condensation flux calculation, this method helps to improve accuracy without a significant expense of computation cost, and it can be applied in a wider range of atmospheric conditions such as in extremely cold atmospheres and polluted exhaust plumes.

Enhancing ammonia sensing performance of Ag2MoO4-based mixed-potential sensor by introducing ionic and electronic conductance

The breath ammonia detection is crucial for the evaluation of the pathological state. Among the existing ammonia detection technologies, the mixed potential sensor exhibits promising potential owing to its high stability, good selectivity and small size. However, it remains challenging in application due to its insufficient limit of detection (LOD). To improve the performance of such sensor, a novel sensing material Ag2MoO4 was synthesized in this work. The electrode morphology was tuned for optimum performance by adjusting the sintering temperature. The response to 5 ppm NH3 at 425 °C is about −29.86 mV with response/recover times of 105/96 s and sensitivity of −49.55 mV/decade. In addition, the sensor exhibits good selectivity and outstanding detection capability of trace-level NH3 as low as 400 ppb. High concentrations of water vapor and CO2 can greatly affect its performance, but it can be easily eliminated by a filter. The research of its sensing mechanism reveals that Ag2MoO4 has both ionic conductance and electronic conductance, which transforms the electrochemical reaction site from two-dimensional three-phase boundaries (TPB) to a three-dimensional one distributed within the sensing material. Specifically, the sensor shows excellent NH3 detection ability with the number of reaction sites increases.