High-performance Ammonia Research Articles

γ- WO3 decorated MXene: An advanced nanomaterial for room temperature operable enhanced ammonia sensor

The proliferation of Internet of Things (IoT) applications necessitates the deployment of high-performance ammonia (NH3) sensors. In recent studies, Ti3C2Tx, a novel two-dimensional (2D) material, has been extensively investigated for its potential as a room temperature NH3 sensor. However, pristine MXene-based sensors have exhibited deficiencies in long-term stability and reproducibility. In response, an MXene/γ-WO3 composite has been synthesized using an ultra-sonication method to address these challenges. The resulting composite sensor has demonstrated remarkable performance, attributable to, increased active sites from defects induced by WO3, and the presence of a p-n heterojunction. Notably, electron transfer from WO3 to Ti3C2Tx has been identified as a critical contributing factor to the enhanced characteristics of these nanohybrids, as evidenced by observed alterations in binding energies for the Ti 2p and W 4f core levels. These findings have expanded our understanding of the electrical interactions in Ti3C2/WO3 and their potential applications in diverse domains. The pristine MXene sensor exhibited a response of 59.39% at 300 ppm at room temperature, while the composite MXene/γ-WO3 displayed a response of 92.3%. Additionally, the response recovery time was recorded at 22seconds and 9seconds, respectively. The chemiresistive ammonia sensor's performance was evaluated across a range of concentrations (25–300 ppm) and relative humidity levels (11–94% RH). The composite sensor has demonstrated reproducibility and long-term stability, coupled with high sensitivity to NH3. This manuscript aims to highlight the enhanced ammonia sensing properties and selectivity of MXene/γ-WO3 composite materials.

Preparation and mechanism study of highly sensitive NH3 gas sensor based on Au-modified CdS nanoparticles

A high-performance ammonia (NH3) gas sensor based on Au nanoparticles (AuNPs) modified CdS (Au/CdS) was synthesized by hydrothermal method, and the sensing mechanism of Au/CdS was studied by first-principles based on density functional theory (DFT). Experimental results show that the addition of AuNPs can effectively enhance CdS-based NH3 gas sensor performance. Au/CdS sensor exhibits high response (16580), short response/recovery time (2.25 s/1.25 s), and low limit detection (500 ppb), good repeatability and stability. Because AuNPs can effectively increase the generation of sulfur vacancies on the surface of CdS, increasing the amount of chemisorbed oxygen and providing more active sites for NH3. Furthermore, the good conductivity of AuNPs promotes the separation and transport of carriers on CdS surface, thereby improving the gas sensing performance. DFT calculations indicate that the ionization energy of Au is less than that of Cd, which causes some Cd atoms to lose their coordination with S atoms and increase sulfur vacancies on the surface of CdS. In Au/CdS sensors, sulfur vacancies accelerate the cleavage of NH3, and resulting electrons participate in charge transport, thereby enhancing the adsorption energy. This study introduces a new method for fabricating high performance NH3 sensor based on CdS rich in sulfur vacancies.

Enhanced ammonia detection using rGO-wrapped Zn3V2O8 nanostructures

This study presents the synthesis and characterization of reduced graphene oxide (rGO)-wrapped Zn3V2O8 nanostructures, highlighting their enhanced ammonia sensing capabilities. Utilizing advanced techniques such as XRD, TEM, HRTEM, XPS, and Raman spectroscopy, the microstructural, compositional, and crystalline properties of the rGO/ Zn3V2O8 composites were thoroughly analyzed. The integration of rGO significantly improves the electrical conductivity, surface area, and chemical reactivity of the Zn3V2O8, resulting in superior sensing performance. Notably, the rGO/Zn3V2O8:2 composite exhibits rapid response and recovery times when detecting ammonia at room temperature, demonstrating its potential as an effective material for advanced gas sensing applications. These findings contribute to the ongoing development of high-performance ammonia sensors, offering a promising approach for real-time environmental monitoring and industrial applications.

Self-Assembled Ti3C2TX MXene Thin Films for High-Performance Ammonia Sensors

MXenes have emerged as a fascinating material for RT gas-sensing applications due to their outstanding properties. This work reports the design and fabrication of a high-performance ammonia sensor based on MXenes material. To improve its sensing performance, a MXenes nanosheets thin film with a thickness of ≈ 10 nm was prepared using a scalable self-assembled method. Specifically, we employed the controlled and enhanced interfacial self-assembled method to fabricate a continuous and conductive MXene ultra-thin film. The morphology and the structure of the produced MXene materials and their films were characterized by combining multi-characterization tools. Altoghether, these highlight the uniform and continuous deposition of the MXene nanosheets film on the glass substrate. The electrical characterization indicates a sheet resistance value of 4.82 × 105 Ω/sq. The fabricated devices present good RT sensing performances for NH3 detection, ranging from 1 to 20 ppm. This demonstrates the outstanding sensitivity of MXene with a value of 1.92 % for the lowest concentration (1 ppm), a fast response (179 s) and a recovery time of (612 s), which is related to the high quality of the ultra-thin MXene sensiting layer. Moreover, the sensors demonstrate high degree of stability and excellent reproducibility, make them suitable candidate for practical applications like environmental monitoring.

High-Performance Ammonia Gas Sensor Based on a Catalytic Ruthenium- Gated Field-Effect Transistor

High-Performance Ammonia Gas Sensor Based on a Catalytic Ruthenium- Gated Field-Effect Transistor

Development of high performance ammonia sensor based on Al doped SnO2 operable at room temperature

This study aims to synthesize Al-doped SnO2 nanostructures using a sol–gel process and investigate their gas-sensing properties, notably ammonia (NH3) detection at ambient temperature. X-ray diffraction (XRD) examination validated the tetragonal crystal structure of the produced Al: SnO2 materials. Field emission scanning electron microscopy (FE-SEM) images showed aggregation of the prepared samples. Transmission electron microscopy (TEM) was used to evaluate the structural and morphological properties of AlS-2 and AlS-8, and selected area electron diffraction (SAED) confirms the crystal structure. As the concentration of Al doping in SnO2 nanostructures increased, the optical band gap (Eg) values decreased. The chemical composition was analyzed using X-ray photoelectron spectroscopy (XPS). Gas sensing studies were conducted on NH3 gas concentrations ranging from 5 to 300 ppm, and AlS-8 emerged as the most promising sensor, with substantial responsiveness, rapid response, recovery durations (21 s/18 s), and linear behavior at ambient temperature. This improved performance shows that AlS-8 has the potential to be an excellent NH3 detector, due to the higher adsorption of oxygen species made possible by Al doping. Surprisingly, continuous measurements over 30 days at five-day intervals revealed significant reactivity of the AlS-8 sensor even at concentrations as low as 100 ppm of NH3 gas.

Engineering hierarchical heterostructure material based on multiwalled carbon nanotubes/SnO2 nanorod-flowers for high-efficient ammonia detection

The rational manufacturing of multi-component materials with rich heterostructure is emerging as a possible strategy to develop improved carbon nanotube-based gas sensors. Herein, hierarchical heterostructure of multiwalled carbon nanotubes/SnO2 nanorod-flowers (HMCNS) was synthesized by a facile water-bathing combined hydrothermal approach for highly sensitive ammonia detection. Exploration in the microstructure reveals that hierarchical flowers-like SnO2 consisted of nanorods demonstrates a hollow geometry for wrapping multiwalled carbon nanotubes, featuring a unique three-dimensional (3D) hierarchical architecture. Gas sensor based on SnO2@4.5%CNTs hierarchical heterostructure exhibits highly enhanced ammonia-sensing performances, including ultra-high response of 1650 toward 20 ppm ammonia, good selectivity, 250 ppb level detection, and superior long-term stability. The improvement in ammonia sensing capability could be attributed to the peculiar hierarchical architecture and the creation of Mott-Schottky heterostructure which has been strongly validated by electrochemical research. This work will provide a concise and effective avenue to construct hierarchical composite with Mott-Schottky heterostructure for high-performance ammonia gas sensor.

Insights into the Origin of Activity Enhancement via Tuning Electronic Structure of Cu2O towards Electrocatalytic Ammonia Synthesis.

The insight of the activity phase and reaction mechanism is vital for developing high-performance ammonia synthesis electrocatalysts. In this study, the origin of the electronic-dependent activity for the model Cu2O catalyst toward ammonia electrosynthesis with nitrate was probed. The modulation of the electronic state and oxygen vacancy content of Cu2O was realized by doping with halogen elements (Cl, Br, I). The electrocatalytic experiments showed that the activity of the ammonia production depends strongly on the electronic states in Cu2O. With increased electronic state defects in Cu2O, the ammonia synthesis performance increased first and then decreased. The Cu2O/Br with electronic defects in the middle showed the highest ammonia yield of 11.4 g h-1 g-1 at -1.0 V (vs. RHE), indicating that the pattern of change in optimal ammonia activity is consistent with the phenomenon of volcano curves in reaction chemistry. This work highlights a promising route for designing NO3-RR to NH3 catalysts.

A portable electrochemical room-temperature sensor based on flower-like structure UIO-66-NH2@MoS2 composite for ammonia detection

Due to the toxicity and corrosiveness of the ammonia gas, low-cost, portable, and accurate methods of ammonia detection are of great importance in environmental testing and disease diagnosis. In this study, flower-like UIO-66-NH2@MoS2 composite modified screen-printed electrodes (SPEs) were prepared by hydrothermal treatment using ionic liquids [BMIM][BF4] as electrolytes. The UIO-66-NH2@MoS2/SPEs were then combined with a miniature electrochemical workstation to construct a novel electrochemical ammonia sensor. The experimental results showed that UIO-66-NH2@MoS2 had excellent adsorption capacity for ammonia, exhibiting good linearity in the range of 5–500 ppm with a low limit of detection (2.1 ppm) and a fast response time for 100 ppm ammonia (13 s). This sensor also possessed excellent stability, reproducibility, and anti-interference ability. The synthesized UIO-66-NH2@MoS2 nanocomposite was demonstrated to be an excellent candidate for the construction of high-performance ammonia sensors for various applications.

High-Performance Ammonia Electrosynthesis from Nitrate in a NaOH-KOH-H2O Ternary Electrolyte.

A glut of dinitrogen-derived ammonia (NH3) over the past century has resulted in a heavily imbalanced nitrogen cycle and consequently, the large-scale accumulation of reactive nitrogen such as nitrates in our ecosystems has led to detrimental environmental issues. Electrocatalytic upcycling of waste nitrogen back into NH3 holds promise in mitigating these environmental impacts and reducing reliance on the energy-intensive Haber-Bosch process. Herein, we report a high-performance electrolyzer using an ultrahigh alkalinity electrolyte, NaOH-KOH-H2O, for low-cost NH3 electrosynthesis. At 3,000 mA/cm2, the device with a Fe-Cu-Ni ternary catalyst achieves an unprecedented faradaic efficiency (FE) of 92.5±1.5 % under a low cell voltage of 3.83 V; whereas at 1,000 mA/cm2, an FE of 96.5±4.8 % under a cell voltage of only 2.40 V was achieved. Techno-economic analysis revealed that our device cuts the levelized cost of ammonia electrosynthesis by ~40 % ($30.68 for Fe-Cu-Ni vs. $48.53 for Ni foam per kmol-NH3). The NaOH-KOH-H2O electrolyte together with the Fe-Cu-Ni ternary catalyst can enable the high-throughput nitrate-to-ammonia applications for affordable and scalable real-world wastewater treatments.

TiO2 decorated MXene nanosheets for high-performance ammonia gas sensing at room-temperature

A room-temperature sensor with superior performance to detect traces of toxic gas molecules is highly desirable. MXenes, due to their unique planar structure, higher electrical conductivity and abundant functional groups on the surface, have emerged as leading low dimensional gas sensing materials. But, the gas sensors based on Ti3C2Tx MXene possess higher detection limit and poor long-term stability, thereby limiting their applications. However, TiO2 modified Ti3C2Tx as a gas sensing platform has displayed improved ammonia sensing performance. Here, we report a facile method to prepare Ti3C2Tx/TiO2 composite via calcination of Ti3C2Tx. The experimental results indicate that the oxidation temperature plays a key role in the morphology evolution and gas-sensing performance of Ti3C2/TiO2 composites. Compared to the as obtained Ti3C2Tx, the Ti3C2Tx/TiO2 composite obtained at 200 °C displays improved response to NH3 gas due to the formation of a heterointerface between Ti3C2Tx and TiO2. Room-temperature, selective ammonia detection down to 5 ppb has been obtained. Moreover, the device displayed a stable sensing response to 10 ppb of ammonia over the RH range of 26%–90%. It also displayed higher selectivity to NH3 over other analytes including dimethyl formamide, ethanol, isopropyl alcohol, methanol, acetone, chloroform, xylene and N-methyl pyrolidone. The results suggest that by appropriate engineering of the Ti3C2Tx/TiO2 composites, ammonia sensor with improved sensing performance can be designed.

A Co3O4/graphdiyne heterointerface for efficient ammonia production from nitrates

The nitrate reduction reaction (NtRR) has been demonstrated to be a promising way for obtaining ammonia (NH3) by converting NO3− to NH3. Here we report the controlled synthesis of cobalt tetroxide/graphdiyne heterostructured nanowires (Co3O4/GDY NWs) by a simple two-step process including the synthesis of Co3O4 NWs and the following growth of GDY using hexaethynylbenzene as the precursor at 110 °C for 10 h. Detailed scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman characterization confirmed the synthesis of a Co3O4/GDY heterointerface with the formation of sp-C―Co bonds at the interface and incomplete charge transfer between GDY and Co, which provide a continuous supply of electrons for the catalytic reaction and ensure a rapid NtRR. Because of these advantages, Co3O4/GDY NWs had an excellent NtRR performance with a high NH3 yield rate (YNH3) of 0.78 mmol h−1 cm−2 and a Faraday efficiency (FE) of 92.45% at −1.05 V (vs. RHE). This work provides a general approach for synthesizing heterostructures that can drive high-performance ammonia production from wastewater under ambient conditions.

High-performance ammonia gas sensor based on spray pyrolysis developed In2O3:La films

La doped indium oxide (In2O3:La) thin films were deposited on glass substrate by nebulizer spray pyrolysis by different La doping concentrations. The crystalline structure, morphology, optical and gas sensing properties of thin films were investigated. XRD diffractograms present cubic crystal structure of In2O3 films, with decreased crystallite size with the incorporation of La dopants. SEM analysis of thin film samples exhibits approximately cube-shaped morphology without any cracks of microstructures. The optical band gap magnitude shows shift in energy values in the range of 3.12–3.29 eV with increasing La concentrations. For all films, the photoluminescence spectra showed violet-blue emission peaks at around 420–480 nm. All of the developed films were tested for ammonia (NH3) gas detection at ambient temperature. In2O3:La 5% sensor had the highest gas response value of 1720%, a quicker response and recovery times of 48/12 s, respectively, suggesting the sample could be better suited for the application of NH3 gas sensor.

Interfacially Confined Dynamic Reaction Resulted to Fluorescent Nanofilms Depicting High-Performance Ammonia Sensing.

Sensing materials innovation plays a crucial role in the development of high-performance film-based fluorescent sensors (FFSs). In our current study, we present the innovative fabrication of four fluorescent nanofilms via interfacially confined dynamic reaction of a specially designed fluorescent building block, a new boron-coordinated compound (NI-CHO), with a chosen one, benzene-1,3,5-tricarbohydrazide (BTH). The nanofilms as prepared are robust, uniform, flexible, and thickness tunable, at least from 40 to 1500 nm. The fabricated FFSs based on Film 3, one of the four nanofilms, shows highly selective and fully reversible response to NH3 vapor with an experimental detection limit of <0.1 ppm and a response time of 0.2 s. The unprecedented high performance of the nanofilm is ascribed to the specific quenching of its fluorescence emission owing to formation of an excited-state complex between the sensing unit and the analyte molecule. Efficient mass transfer also contributes to the high performance owing to the porous adlayer structure of the nanofilm. This work provides an example to show how to develop a high-performance sensing film via controlling the film's structure, especially the thickness.

Construction of Co/CeO2 catalyst and study on catalytic performance

High-temperature ammonia decomposition is a promising method for hydrogen production, but high temperatures and low conversion rates limit its wide application. In order to solve this problem, the development of nano-materials is essential to achieve high performance ammonia oxidation decomposition. In this paper, ordered mesoporous Co/CeO2 catalyst was synthesized by codeposition method and a new process of ammonia hydrogen production was developed and designed without the need for external heating. The catalyst was characterized by XRD, BET and TEM. The results show that the catalyst activity is the highest when Co content is 10wt%. When the molar ratio of NH3/O2 is 4:1, the bed temperature increases from 165°C to 405°C, the conversion rate of NH3 and O2 is 72% and 81%, respectively, and the productivity of H2 is 45%. The catalyst also showed good stability and reusability.

Inkjet-printed Pt/WO3 thin film sensor for ppb-level ammonia detection

The development of high-performance ammonia sensors is crucial for environmental monitoring and human health protection. However, traditional conductive metal oxide gas sensors encounter significant challenges such as poor selectivity and high detection limit, mainly raising from their inherent cross-sensitivity and thick gas-sensing layer caused by uncontrollable preparation. Herein, a noble metal platinum-modified tungsten oxide (Pt/WO3) gas sensor is controllably fabricated via inkjet printing technology and magnetron sputtering. In addition to a detection limit toward ammonia as low as 40 ppb, the Pt/WO3 gas sensor demonstrates a good selectivity for ammonia compared to other interfering gases, including acetone, sulfur dioxide, formaldehyde, methane, sulfur hexafluoride, and toluene, with corresponding selectivity coefficients not less than 4.7. The high sensitivity of the gas sensor is mainly attributed to the fact that more electrons can be directly controlled by the adsorbed gas benefiting from the micro-nano thickness of the sensing layer, as well as additional adsorption sites are provided by the Pt modification. Moreover, the catalytic effect of Pt on the reaction between ammonia and oxygen ions further enhances its sensitivity while also improving its selectivity. Our work establishes an important theoretical and experimental foundation for the design of high-performance ammonia sensors.

Dog nose-inspired high-performance ammonia sensor based on biochar/SnO2 composite

Inspired by the ordered tubular structure inside the dog nose and its olfactory receptors, this paper reports a biochar/SnO2 composite based on waste disposable bamboo chopsticks (DBC) combined with tin dioxide (SnO2) nanoparticles. The response of optimized biochar/SnO2 composite reaches 4513 to 500 ppm NH3, and the response/recovery times are 50.4 s and 3.7 s, respectively. The biochar/SnO2 composite displays the dog-nose-like ultra-fast response (1 s response up to 1100) to 500 ppm NH3 at room temperature (25 °C), which makes the biochar/SnO2 composite with the application promising for rapid detection of NH3. The optimized biochar/SnO2 sensor also exhibits good selectivity and linear response with a theoretical detection limit as low as 34 ppb NH3. In addition, the biochar/SnO2 sensor has reliable humidity immunity and long-term stability. Within a period of up to six months, the response fluctuation of biochar/SnO2 sensor to 500 ppm NH3 at 25 °C is less than 3.7%. However, the susceptibility of biochar/SnO2 composite to the operating temperature need to be overcome. The biochar/SnO2 composite was prepared by low-temperature pyrolytic carbonization (300 °C) with the advantages of abundant raw materials, low cost and green environmental protection, providing a new outlet for solid waste.

CeO2‒x modified Ru/γ-Al2O3 catalysts for ammonia decomposition reaction

Developing high-performance ammonia decomposition catalysts for preparing COx-free hydrogen shows great practical significance. Herein, CeO2 is used as a promoter to modulate the metal-support interaction to enhance the catalytic performance of Ru/Al2O3 catalysts. A series of 1Ru/xCe-10Al (x = 0.5, 1, or 3) catalysts was prepared by a facile colloidal deposition method. We find that the optimized 1Ru/1Ce–10Al catalyst exhibits excellent activity for the decomposition of ammonia with a very high hydrogen yield of 7097 mmolH2/(gRu·min) at 450 °C. It is confirmed that Ru species are highly dispersed on the support surface as stable small clusters (∼1.3 nm). More importantly, due to the interaction between Ru species and partially reduced CeO2–x, the electron density of Ru species is increased, which is beneficial to the high activity of the 1Ru/xCe-10Al catalysts. This work paves a way to construct high-efficiency ammonia decomposition catalysts modified by CeO2.

Specifically adsorbed ferrous ions modulate interfacial affinity for high-rate ammonia electrosynthesis from nitrate in neutral media

The electrolysis of nitrate reduction to ammonia (NRA) is promising for obtaining value-added chemicals and mitigating environmental concerns. Recently, catalysts with high-performance ammonia synthesis from nitrate has been achieved under alkaline or acidic conditions. However, NRA in neutral solution still suffers from the low yield rate and selectivity of ammonia due to the low binding affinity and nucleophilicity of NO3-. Here, we confirmed that the in-situ-generated Fe(II) ions existed as specifically adsorbed cations in the inner Helmholtz plane (IHP) with a low redox potential. Inspired by this, a strategy (Fe-IHP strategy) was proposed to enhance NRA activity by tuning the affinity of the electrode-electrolyte interface. The specifically adsorbed Fe(II) ions [SA-Fe(II)] greatly alleviated the electrostatic repulsion around the interfaceresulting in a 10-fold lower in the adsorption-free energy of NO3- when compared to the case without SA-Fe(II). Meanwhile, the modulated interface accelerated the kinetic mass transfer process by 25 folds compared to the control. Under neutral conditions, a Faraday efficiency of 99.6%, a selectivity of 99%, and an extremely high NH3 yield rate of 485.8 mmol h-1 g-1 FeOOH were achieved. Theoretical calculations and in-situ Raman spectroscopy confirmed the electron-rich state of the SA-Fe(II) donated to p orbitals of N atom and favored the hydrogenation of *NO to *NOH for promoting the formation of high-selectivity ammonia. In sum, these findings complement the textbook on the specific adsorption of cations and provide insights into the design of low-cost NRA catalysts with efficient ammonia synthesis.

Sustainable waste-nitrogen upcycling enabled by low-concentration nitrate electrodialysis and high-performance ammonia electrosynthesis

A product-oriented electrolyzer design offers a remarkably high nitrate-to-ammonia performance on a simple nickel electrode in an aqueous NaOH/KOH/H2O electrolyte.