Ppm NH3 Research Articles

Enhanced ammonia sensing performance based on MXene-Ti3C2Tx multilayer nanoflakes functionalized by tungsten trioxide nanoparticles

Low-power consumption and high sensitivity are highly desirable for a vast range of NH3 sensing applications. As a new type of two-dimension (2D) material, Ti3C2Tx is extensively studied for room temperature NH3 sensors recently. However, the Ti3C2Tx MXene based gas sensors suffer mainly from low sensitivity. Herein, we report a sensitive Ti3C2Tx/WO3 composite resistive sensor for NH3 detection. The Ti3C2Tx/WO3 composite consisting of WO3 nanoparticles anchored on Ti3C2Tx nanoflakes were synthesized successfully with a facile ultra-sonication technique. The composite sensor with optimized components exhibits a high sensitivity of 22.3% for 1 ppm NH3 at room temperature, which is 15.4 times higher than the pure Ti3C2Tx sensor. Furthermore, the composite sensor has excellent reproducibility, good long-term stability, and high selectivity to NH3. The relative humidity influence on NH3 gas sensing properties of the sensors was systematically studied. This research provides an efficient route for the preparation of novel MXene-based sensitive materials for high-performance NH3 sensors.

Highly Sensitive Ammonia Gas Detection at Room Temperature by Integratable Silicon Nanowire Field-Effect Sensors.

Toxic gas monitoring at room temperature (RT) is of great concern to public health and safety, where ultrathin silicon nanowires (SiNWs), with diameter <80 nm, are ideal one-dimensional candidates to achieve high-performance field-effect sensing. However, a precise integration of the tiny SiNWs as active gas sensor channels has not been possible except for the use of expensive and inefficient electron beam lithography and etching. In this work, we demonstrate an integratable fabrication of field-effect sensors based on orderly SiNW arrays, produced via step-guided in-plane solid-liquid-solid growth. The back-gated SiNW sensors can be tuned into suitable subthreshold detection regime to achieve an outstanding field-effect sensitivity (75.8% @ 100 ppm NH3), low detection limit (100 ppb), and excellent selectivity to NH3 gas at RT, with fast response/recovery time scales (Tres/Trec) of 20 s (at 100 ppb NH3) and excellent repeatability and high stability over 180 days. These outstanding sensing performances can be attributed to the fast charge transfer between adsorbed NH3 molecules and the exposed SiNW channels, indicating a convenient strategy to fabricate and deploy high-performance gas detectors that are widely needed in the booming marketplace of wearable or portable electronics.

CsPbI3NC-Sensitized SnO2/Multiple-Walled Carbon Nanotube Self-Assembled Nanomaterials with Highly Selective and Sensitive NH3 Sensing Performance at Room Temperature.

It is an effective strategy to enhance the sensitivity of semiconductor metal oxides (SMOs) being sensitized with CsPbI3 nanocrystals (NCs) by adjusting the heterostructure between CsPbI3NC and SMO nanomaterials. In this work, for the first time, a porous 3D multiple-walled carbon nanotube (MWCNT) network uniformly coated with SnO2 quantum nanoparticles (QNPs) and CsPbI3 nanocrystals were prepared via a simple solvent vapor-induced self-assembly method. The fabricated CsPbI3NC-SnO2QNP/MWCNT nanocomposite with vapor-induced self-assembly exhibits superior stability against the moisture as well as an excellent sensing response. The results imply that the rational design of the metal halide perovskite NC/SMO heterostructure can not only improve the stability but also meet the requirements of sensing application. The self-assembled SnO2QNP/MWCNT can facilitate the dispersion of small-sized nanoparticles and efficaciously prevent the detachment of CsPbI3NC. Compared with pristine SnO2QNP and SnO2/MWCNT sensors, the CsPbI3NC-modified SnO2QNP/MWCNT nanostructure exhibited a remarkable sensitivity of 39.2 for 0.2 ppm NH3, rapid response/recovery time of 17/18 s, and excellent selectivity towards NH3. In particular, we applied machine learning methods, including principal component analysis (PCA) and support vector machines (SVMs), to analyze the sensing performance of the CsPbI3NC-SnO2QNP/MWCNT sensor and found that the combined effects of CsPbI3NC-SnO2QNP/MWCNT heterointerfaces contributed to the improvement of selectivity of sensors. The excellent NH3 for sub-ppm level concentration is ascribed to the high sensing activity of the CsPbI3 NC-based heterojunction. This work may not only enrich the family of high-performance breath detection materials but also provide a good example for designing reasonable composite materials with specific properties in the field of metal halide perovskite/SMO heterojunctions.

Preparation and Characterization of Mixed In2O3 –AgxO Nanostructure Thin Films on porous silicon as NH3 High Gas Sensor

Mixed nanostructured thin films composed of In2O3 – AgxO, were synthesized on glass and porous silicon to produce NH3-gas sensor. The films’ structure of the sensor was analyzed by XRD and AFM. The results obtained that polycrystalline nanostructure thin films were prepared. The optical properties indicate that the transmission and the energy gap were decreased with the increase in AgxO ratio. The sensor conductivity changed from n-type for In2O3 up to 10 Vol% AgxO to p-type with mixed oxides. The synthesis gas sensor gives sensitivity toward 40 ppm NH3 gas at different temperatures (50, 100, 150 and 200) ˚C. The maximum sensitivity of mixed films on porous silicon for 15% AgxO ratio is 94.13% with a response time of 11.85 s and a recovery time of 20 s. Porous silicon improves the sensitivity of the prepared sensor by a factor of two with respect to the sensor over the glass. The good sensor properties of In2O3 – AgxO nanostructure mixed oxide at a low temperature indicated as highly efficient NH3 gas sensor.

Ultra-sensitive clogging free combustible molecular precursor-based screen-printed ZnO sensors: a detection of ammonia and formaldehyde breath markers

It is beneficial to develop the cost-effective, ultra-sensitive ZnO-based sensor for the rapid detection and quantification of the ammonia and formaldehyde breath markers under ambient conditions. Here, one-step solution route was adopted to formulate the aqueous combustible molecular precursor-based clogging free screen-printing ink consisting of zinc nitrate as an oxidizer, glycine as fuel, and eco-friendly binder sodium carboxymethylcellulose. The formulated precursor was deposited on the glass substrates via a screen-printing technique followed by annealing at different temperatures for an hour. Screen printed ZnO sensors processed at 500 °C with high crystallinity, less lattice distortion, low optical bandgap, and high concentration of donor defects showed remarkably high NH3 gas response ~ 336 and a moderate HCHO response ~ 16.4 towards the 5 ppm and 10 ppm of the respective gases. In addition it's LOD values is drawn as 0.6 ppm and 2.9 ppm for NH3 and HCHO gases, respectively, and exhibits superior selectivity towards ammonia. Faster diffusion of oxygen vacancies (Vo) in the smaller crystallites resulted expeditious sensor kinetics in the screen-printed sensor processed at 400 °C. Response and recovery time were recorded to be 50 s and 50 s to the 5 ppm of NH3, respectively. The crystallinity-dominant domain overcomes the adverse effect of larger grains on the gas response of screen-printed ZnO sensor processed at 500 °C. Robust, scalable, and cost-effective screen-printed ZnO conductometric sensors demonstrated here has a potential application in clinical diagnosis, and also in monitoring the NH3 and HCHO gases at low ppm-level.

Bulk tungsten-substituted vanadium oxide for low-temperature NOx removal in the presence of water

NH3-SCR (selective catalytic reduction) is important process for removal of NOx. However, water vapor included in exhaust gases critically inhibits the reaction in a low temperature range. Here, we report bulk W-substituted vanadium oxide catalysts for NH3-SCR at a low temperature (100–150 °C) and in the presence of water (~20 vol%). The 3.5 mol% W-substituted vanadium oxide shows >99% (dry) and ~93% (wet, 5–20 vol% water) NO conversion at 150 °C (250 ppm NO, 250 ppm NH3, 4% O2, SV = 40000 mL h−1 gcat−1). Lewis acid sites of W-substituted vanadium oxide are converted to Brønsted acid sites under a wet condition while the distribution of Brønsted and Lewis acid sites does not change without tungsten. NH4+ species adsorbed on Brønsted acid sites react with NO accompanied by the reduction of V5+ sites at 150 °C. The high redox ability and reactivity of Brønsted acid sites are observed for bulk W-substituted vanadium oxide at a low temperature in the presence of water, and thus the catalytic cycle is less affected by water vapor.

4Cu-ZSM-5 catalyst for the selective catalytic reduction of NO with NH3 and oxidation of elemental mercury

4Cu-ZSM-5 catalyst was synthesized using microwave wet impregnation for simultaneous removal of NO and elemental mercury (Hg0) from simulated flue gas. The highest removal efficiencies were achieved at 250 C for both NO (96.5%) and Hg0 (84.5%). Meantime, the effect of O2, NH3 and SO2 were investigated. The results showed that 5% O2 and 500 ppm NH3 made the removal efficiencies be the highest and after the addition of 100 ppm SO2, the removal efficiencies reduced to 40% for NO and 55% for Hg0. According to the characterization results, 4Cu-ZSM-5 had better thermal stability abundant reducing substances and richer weak acid sites for the simultaneous removal of NO and Hg0. NO formed bridging nitrates on the 4Cu-ZSM-5 surface and then combined with NH3 to form Lewis acid sites for reducing to N2. Meanwhile, Cu2+ induced Hg0 to give electrons, making it oxidized to HgO.

The gas sensor utilizing polyaniline/ MoS2 nanosheets/ SnO2 nanotubes for the room temperature detection of ammonia

In this work, we developed a NH3 gas sensor based on polyaniline (PANI) composited with MoS2 nanosheet-coated SnO2 nanotubes (PMS) via electrostatic spinning, hydrothermal route and in-situ polymerization technique. The morphologies, nanostructures and compositions of the materials were obtained from X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FESEM), Transmission electron microscope (TEM) and Brunauer-Emmett-Teller method (BET). Thanks to nanostructure and the synergistic properties of PANI and MoS2/SnO2, the designed PMS gas sensor exhibited response signal of 10.9 towards 100 ppm NH3 at room temperature and a low detection limit of 200 ppb with good response-recovery time, good repeatability, acceptable flexibility and excellent selectivity. This study offers a versatile platform to modify PANI for highly selective detection of NH3 gas sensor at room temperature.

Ultralow-detection limit ammonia gas sensors at room temperature based on MWCNT/WO3 nanocomposite and effect of humidity

Nanocomposite-based NH3 gas sensors working at room temperature were systematically fabricated by compositing multi-walled carbon nanotubes (MWCNTs) and tungsten oxide (WO3) nanobricks at different mass ratios. The response of the nanocomposite-based sensors increases with increasing WO3 content from 0 to 95 wt% then decreases as the WO3 content continuously increases to 100 wt%. The sensor with 95 wt% of WO3 shows a significant enhancement in NH3 gas sensing characteristics, namely, high response (~350% with 60 ppm NH3), ultralow limit of detection (6 ppb), and selectivity to NH3. The enhancement of gas sensing characteristics was attributed to the synergistic effect of the p-p junction between MWCNT and the inversion layer on the WO3 surface caused by the adsorbed oxygen gas and water vapor in ambient air. The response increases while the sensor's resistance decreases with increasing relative humidity from 25% to 65%. Hence, MWCNT/WO3 nanocomposite is a promising material for selective sub-ppm NH3 gas sensor at room temperature.

Modeling and Optimization of Multi-functional Ammonia Slip Catalysts for Diesel Exhaust Aftertreatment

Ammonia slip catalysts (ASC) are used downstream of the NH3-selective catalytic NOx reduction (SCR) system, to minimize ammonia slip from transport sector SCR units. The ASC may consist of an SCR active layer for NOx control, a layer with oxidation functionality for ammonia conversion, or a combination thereof, either as individual layers or as a single mixed layer. Mathematical models of such systems involve flow and mass transfer in the monolithic channels as well as coupled reaction/diffusion processes in the catalytic layers. In this work, we develop a single-channel 1D-1D (pseudo 2D) steady-state tank-in-series mathematical model for monolithic ammonia slip catalysts with up to two layers. Kinetics of relevant reactions over the Cu-Beta zeolite and the Pt/TiO2 layer, including SCR, ammonia oxidation, and the formation of N2O, were derived based on an extensive flow reactor study. The model was validated based on experiments using four different small-scale ASC monoliths, showing good agreement between the model predictions and the experimental results. Comparison of ten ASC configurations for the oxidation of 200 ppm NH3 at 300 °C shows that configurations with a pure layer of NH3 oxidation catalyst generate undesirable high N2O and NOx levels. The best ASC configurations feature fast diffusion in the catalytic layers (a high effective diffusion coefficient), a thin top layer loading with some ammonia oxidation catalyst, and a mixed layer of ammonia oxidation catalyst and the SCR catalyst to limit the formation of N2O and NOx.

Porous metal-graphene oxide nanocomposite sensors with high ammonia detectability

Nickel oxide-graphene oxide (NiO-GO), zinc oxide-graphene oxide (ZnO-GO) and bismuth oxide-graphene oxide (Bi2O3-GO) metal oxide-graphene oxide nanocomposite (MO-GO NC) sensors, operable at room temperature, were synthesized via a simple and cost-effective microwave-assisted combustion method for chemiresistive gas sensor applications. From the measured structural, morphological, and elemental detection properties, the sensors are found capable of detecting various gases. The Bi2O3-GO NC sensor exhibited excellent response over NiO-GO (~20 at 50 ppm) and ZnO-GO NC (~60 at 50 ppm) sensors for detecting NH3. The response of the Bi2O3-GO NC sensor at 50 ppm NH3 in just 14 s operation duration was ~81.23, which is improved 25-fold and 13-fold compared to pristine GO sensors. Additionally, the as-developed Bi2O3-GO NC sensor demonstrates outstanding repeatability and recovery kinetics, attributed to porosity and the combined effects of MO and GO. The sensing mechanism of the Bi2O3-GO NC gas sensors is proposed herein. The superior sensing performance, including quick response and recovery of the Bi2O3-GO NC sensor is attributed to favorable charge transfer across the Bi2O3 and GO interface. The significance of relative humidity on sensing potential of the Bi2O3-GO NC sensor has also been studied and the sensor is confirmed to be unaffected by relative humidity.

Kinetics of NH3 oxidation on Pt/Al2O3: Rate enhancement and NH3 inhibition

We describe a combined experimental kinetics and modeling study for NH3 oxidation on Pt/Al2O3 and development of a predictive microkinetic model valid over a range of conditions. The NH3 oxidation rate (TOF) dependence is reported for NH3 concentrations between 10 and 25,000 ppm and temperatures below 250°C for Pt/Al2O3 powder and washcoated monoliths. The data reveal a shift from positive- to negative-order rate dependence on NH3 with the rate maximum dependent on the processing of Pt/Al2O3; unmilled Pt/Al2O3 powder exhibits a rate maximum at 500 ppm NH3, while ball-milled Pt/Al2O3 has a maximum at ~10,000 ppm. This unexpected enhancement of Pt/Al2O3 activity from milling results in a lowering of the light-off temperature (T50) by up to 100°C. Further examination rules out the extent of pore diffusion limitations as the root cause, but rather an increase in the fraction of stepped crystalline planes and destabilization of Pt oxide shown from XRD and H2-TPR characterization. The dependence of a shift in the rate maximum to higher NH3 concentrations with milling extent is shown to require single- and dual-site reaction pathways. The kinetic scheme also captures a subtle shift in the apparent NH3 reaction order for both unmilled and milled Pt/Al2O3. The microkinetic scheme is incorporated into fixed-bed and monolith reactor models which show excellent agreement with the NH3 conversion and product distribution data.

Room temperature flexible NH3 sensor based on polyaniline coated Rh-doped SnO2 hollow nanotubes

In this work, polyaniline (PANI) coated Rh-doped SnO2 hollow nanotubes (PRS) were synthesized via electrostatic spinning and in-situ polymerization technique. The obtained samples were characterized by X-ray diffractometer, Field emission scanning electron microscopy, Transmission electron microscopy, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller. The gas sensing performances of the sensors based on PRS nanotubes were investigated systematically at room temperature. It was shown that the polyaniline coated 0.5 mol% Rh-doped SnO2 nanotube (PRS0.5) sensor exhibited the highest response value of 13.6 to 100 ppm NH3 at room temperature with excellent selectivity, acceptable repeatability and favorable flexibility. The enhanced gas sensing performances were due to the morphology structure, the heterojunction between PANI and Rh-SnO2 and the catalytic effect of Rh2O3. Thus, the PANI coated Rh-doped SnO2 hollow nanotubes could be a promising candidate for designing and fabricating flexible NH3 gas sensor at room temperature.

Performance of transition metal (Cu, Fe and Co) modified SCR catalysts for simultaneous removal of NO and volatile organic compounds (VOCs) from coal-fired power plant flue gas

Emissions of NO and Volatile Organic Compounds (VOCs) in China are growing rapidly, thus it is necessary to develop a catalyst that can simultaneously remove them. In this study, a series of new V-W/Ti SCR catalysts modified by Cu, Fe and Co were prepared by wet impregnation method, which was used to simultaneously remove NO and typical VOCs (benzene and toluene) from coal-fired power plant flue gas. The catalyst activity evaluation was studied in selective catalytic reduction temperature window (260 °C, 300 °C, 340 °C, 380 °C and 420 °C) by a self-built device. Simulated flue gas was composed of 100 ppm benzene, 100 ppm toluene, 500 ppm NO, 1000 ppm SO2, 500 ppm NH3, 3.33% O2, and balanced N2, whose total flow was 750 mL/min. Characterization techniques such as SEM-EDS, XRD, XPS, and NH3-TPD were used to analyze the effect of Cu, Fe and Co loading on the catalyst's surface properties, physical structure, valence, and acid site, which further explained the removal efficiency result. The experimental results indicated that Cu0.1-V-W/Ti had the best denitration performance at low temperature and reached a maximum NO removal rate of 86.4% at 340 °C. All prepared catalysts had over 90% benzene removal and over 95% toluene removal rate. Cu0.1-V-W/Ti shows certain SO2 tolerance and has the potential to be used for simultaneous removal of NO and VOCs at SCR area of coal-fired power plants without extra capital cost.

Highly sensitive ammonia gas sensor based on metal-organic frameworks-derived CoSe2@nitrogen-doped amorphous carbon decorated with multi-walled carbon nanotubes

This paper presents a high-sensitivity ammonia (NH3) sensor based on nitrogen-doped amorphous carbon-coated cobalt diselenide and multi-walled carbon nanotubes-decorated nano-composite (CoSe2@NC/MWCNTs). In this study, nitrogen-doped amorphous carbon-coated cobalt diselenide (CoSe2@NC) was prepared from a cobalt-based metal-organic framework (MOF) and in situ selenization of cobalt ions. The prepared samples were characterized by all kinds of advanced techniques of SEM, TEM, XPS, XRD and BET. The CoSe2@NC/MWCNTs film was deposited on an epoxy substrate having interdigitated electrode microstructure. The NH3 sensing characteristics of the sensor were studied at room temperature (RT) of 25 °C and 43% relative humidity (RH). The response of the CoSe2@NC/MWCNTs-S2 sensor to 10 ppm NH3 is up to 93.37%, and the sensor can detect NH3 concentration as low as 0.1 ppm. In addition, the effect of humidity on sensor performance was also explored. This significant increase in gas sensing performance is primarily due to the synergistic effects of CoSe2@NC/MWCNTs composite and the effect of p-n heterojunction. The sensor proposed in this work is capable for the NH3 gas detection and human disease diagnosis.

A high-sensitivity graphene ammonia sensor via aerosol jet printing

High-sensitivity ammonia gas sensors are paramount to many fields in our industries and lives. Due to its complicated fabrication processes, large size and long recovery time of most existing ammonia gas sensors, we present a micron-scale graphene-based ammonia gas sensor using aerosol-jet printing technology. The graphene sensor exhibited high response sensitivity (∼4.64 % for 4.35 ppm NH3 and ∼52.01 % for 97.19 ppm NH3, respectively), short adsorption / desorption time ranging from 50 s to 150 s, good reversibility and repeatability. Further employment of micro-heater close to the sensing line reduced desorption time more than ∼14.3 % when 10 V being applied onto the heater. Such design of the ammonia gas sensor by aerosol-jet printing can give an insight for graphene-based ammonia gas sensors, which may pave a way for the convenient integration with other sensors in portable instruments for coal miners and pathfinders etc.

A flexible polypyrrole/silk-fiber ammonia sensor assisted by silica nanosphere template

Flexible polypyrrole (PPy)@silk-fiber and PPy@sponge sensors were fabricated using the silica nanosphere (SiO2 NS) template via a facile in situ chemical oxidation polymerization method. Exposed to 100 ppm NH3 gas at room temperature in 68 ± 5 % relative humidity (RH), the response of the PPy/NS@silk-fiber sensor (73.25 %) was five-fold higher than that of the PPy/NS@sponge sensor (14.51 %). Meanwhile, the recovery time (69 s) of the PPy/NS@silk-fiber sensor was reduced to two-thirds of that (98 s) of the PPy/NS@sponge sensor for 100 ppm NH3. Additionally, the PPy/NS@silk-fiber sensor exhibited excellent reproducibility, flexibility, selectivity, and long-term stability to NH3 at room temperature. The improved gas-sensing properties can be attributed to the high surface area of the flexible PPy/NS@silk-fiber with relative rough hill-like shapes. This investigation indicated that the PPy/NS@silk-fiber is promising sensing material for developing flexible and wearable NH3 sensors.

Hollow Au/Polypyrrole Capsules to Form Porous and Neural Network-Like Nanofibrous Film for Wearable, Super-Rapid, and Ultrasensitive NH3 Sensor at Room Temperature.

Wearable conducting polymer-based NH3 sensors are highly desirable in real-time environmental monitoring and human health protection but still a challenge for their relatively long response/recovery time and moderate sensitivity at room temperature. Herein, we present an effective route to fulfill this challenge by constructing porous and neural network-like Au/polypyrrole (Au/PPy) electrospun nanofibrous film with hollow capsular units for NH3 sensor. Taking the unique architecture and synergistic effect between Au and PPy, our sensor exhibits not only super-rapid response/recovery time (both ∼7 s), faster than all reported sensors, but also stable and ultrahigh sensitivity (response reaches ∼2.3 for 1 ppm NH3) at room temperature even during repeated deformation. Furthermore, good selectivity has been also achieved. These outstanding properties make our sensor hold great potential in real-time NH3-related disease diagnosis and environmental monitoring at room temperature.

NH3 sensing performance of Pt-doped WO3·0.33H2O microshuttles induced from scheelite leaching solution

WO3·0.33H2O microshuttles (WMSs) self-assembled by numerous nanorods along the same direction were prepared based on a cheap tungsten-containing metallurgical raw material by combination processes of NaOH leaching and one-step hydrothermal method. The microstructures and gas sensing properties of various concentrations (0, 0.7, 1.0, and 1.3 mol%) of Pt-doped WMSs were investigated to improve their performance. The microstructural characterizations demonstrated that the WMSs assembled by one-dimensional WO3·0.33H2O nanorods were approximately 0.8–1.9 μm in diameter. Such nanorods exhibited a single hexagonal structure with their diameters ranging from 17 to 62 nm. The gas sensing properties indicated that Pt-doped WMSs showed superior gas sensing performance in terms of the sensor response and NH3 selectivity in the operating temperature range of 25−225 °C as compared with pure one, and simultaneously Pt doping could significantly reduce the detection limit of NH3. Especially, 1.0 mol% Pt-doped WMSs exhibited the highest response of 28.2–1000 ppm NH3 at 175 °C, which was 4 times higher than pure one at 50 °C, indicating that it is a potential candidate material for the detection of NH3 gas.

Influence of Ammonia Contamination on HT-PEM Fuel Cell Platinum Catalyst

High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are considered as one of the promising types of power sources for automobile and stationary application. They have several advantageous characteristics, including high power density and efficiency, high tolerance against CO poisoning as well as zero-emission when using hydrogen and air as fuel and oxidant, respectively[1]. In the last decades HT-PEM fuel cells have been investigated extensively with the aim to introduce them into the market for commercial use.Gas impurities are one of the factors which can limit their durability and life time. Among them ammonia is a feed stream gas impurity which may contaminate the cathode as well as the anode of fuel cells. The main sources of ammonia traces come from hydrogen fuel produced from ammonia and from reforming of fossil fuel that contain species of nitrogen compounds[2]. Moreover, traces of ammonia in ambient air can occur in agricultural areas. The presence of ammonia traces was shown to decrease the performance of low temperature PEM fuel cells [3]. The ammonia species can effect on hydrogen oxidation reaction as well as oxygen reduction reaction affecting the catalyst and leading to reduced efficiency of fuel cells.[3] To the best of our knowledge, the effect of ammonia contamination on HT-PEM fuel cells and in particular on the carbon-supported platinum catalyst has not been fully explored yet. Therefore, the first aim of the present work is to investigate the effect of NH4 + poisoning on carbon-supported platinum in 0.5 mol L-1 H3PO4 in order to simulate the environment of HT-PEMFCs. The oxygen reduction reaction was studied in the presence of 10 ppm NH4 + ions using the rotating ring disk electrode (RRDE). In particular, activity of the Pt/C catalyst was determined before and after poisoning to evaluate the degradation. The effect of contamination on the performance loss, reduction of electrochemical active area and increase of H2O2 formation has been defined by RRDE measurements. In the second part, a commercially available membrane electrode assembly (MEA) was exposed to 10 ppm NH3 inside the air stream using a HT-PEM single cell test bench and applying a constant load of 0.3 A cm-2. Polarization curves and electrochemical impedance spectroscopy were used to investigate changes of the MEA performance. The RRDE study in H3PO4 electrolyte of the catalyst provides in combination with HT-PEM fuel cell testing an increased understanding of the NH3 impact on HT-PEMFC systems.Figure: CVs of Pt/C catalyst in 0.5 M H3PO4 at 50 mV/s in the potential range 0.05 – 1.5 V vs RHE in the absence and in the presence of 10 and 100 ppm NH4 +, respectively.[1] X. Cheng, Z. Shi, N. Glass, L. Zhang, J. Zhang, D. Song, Z.-S. Liu, H. Wang, J. Shen, J. Power Sources 2007, 165, 739-756.[2] X. Zhang, U. Pasaogullari, T. Molter, Int. J. Hydrogen Energy 2009, 34, 9188-9194.[3] F. A. Uribe, S. Gottesfeld, T. A. Zawodzinski, J. Electrochem. Soc. 2002, 149, A293-A296; R. Halseid, P. J. S. Vie, R. Tunold, J. Power Sources 2006, 154, 343-350. Figure 1