NH3 Molecules Research Articles

Breath-by-breath measurement of exhaled ammonia by acetone-modifier positive photoionization ion mobility spectrometry via online dilution and purging sampling

Exhaled ammonia (NH3) is an essential noninvasive biomarker for disease diagnosis. In this study, an acetone-modifier positive photoionization ion mobility spectrometry (AM-PIMS) method was developed for accurate qualitative and quantitative analysis of exhaled NH3 with high selectivity and sensitivity. Acetone was introduced into the drift tube along with the drift gas as a modifier, and the characteristic NH3 product ion peak of (C3H6O)4NH4+ (K0 = 1.45 cm2/V·s) was obtained through the ion-molecule reaction with acetone reactant ions (C3H6O)2H+ (K0 = 1.87 cm2/V·s), which significantly increased the peak-to-peak resolution and improved the accuracy of exhaled NH3 qualitative identification. Moreover, the interference of high humidity and the memory effect of NH3 molecules were significantly reduced via online dilution and purging sampling, thus realizing breath-by-breath measurement. As a result, a wide quantitative range of 5.87–140.92 μmol/L with a response time of 40 ms was achieved, and the exhaled NH3 profile could be synchronized with the concentration curve of exhaled CO2. Finally, the analytical capacity of AM-PIMS was demonstrated by measuring the exhaled NH3 of healthy subjects, demonstrating its great potential for clinical disease diagnosis.

Ammonia gas-sensing behavior of uniform nanostructured PPy film prepared by simple-straightforward in situ chemical vapor oxidation

Abstract A highly uniform nanostructured polypyrrole (PPy) film prepared by a simple, straightforward in situ route of chemical vapor oxidation has been demonstrated as a sensitive substrate for NH3 gas sensing. The structure of PPy film was investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The binding characteristics of the functional groups of the PPy film were examined by Fourier transform infrared and Raman spectroscopy. NH3 sensing properties of the PPy film were evaluated by its resistive response to gas concentrations from 45 to 350 ppm at different temperatures ranging from 25 to 100°C. The sensing response maximum value was 142.6% when exposed to 350 ppm of NH3 gas at room temperature (25°C). The sensing response of PPy film shows an excellent linear relationship and high selectivity toward NH3. The NH3 sensing mechanism is due to the physisorption and chemisorption interactions of NH3 molecules and the adsorptive sites of PPy (polaron and bipolaron charging carriers).

Blended membranes with ionic liquids tailoring by hydroxyl group for efficient NH3 separation

Ionic liquids (ILs)-based membranes are prospective for efficient NH3 separation due to their designability and high gas affinity. This work developed Pebax blended membranes with aprotic IL [EtOHmim][NTf2] and protic IL [EtOHim][NTf2] tailoring by hydroxyl group to improve NH3 separation performance and deeply investigate ILs structure-membrane property-separation performance relationship. The incorporation of ILs remarkably improves NH3 separation performance and leads to different gas transport properties of membranes confirmed by experiments and simulation calculations. The Pebax/EtOHmim-100 blended membrane exhibits exceptional NH3 permeability of 3729.3 barrer, which is 2.65 times higher than that of neat Pebax membrane. The increased FFV and moderate hydrogen bonding interaction simultaneously raise NH3 diffusivity and solubility, resulting in an evident increase of NH3 permeability. Although stronger hydrogen bonding interaction between [EtOHim][NTf2] and NH3 significantly improves NH3 solubility, it also blocks the NH3 fast diffusivity in the membrane, so the NH3 permeability of Pebax/EtOHmim blended membranes is lower than that of Pebax/EtOHmim blended membranes. Moreover, the solubility selectivity depended on interactions between ILs and gas molecules plays a dominant role in the enhancement of NH3 selectivity, thus the highest NH3/N2 selectivity of 1822.3 and NH3/H2 selectivity of 200.7 is obtained by Pebax/EtOHim-100 membrane owing to the stronger hydrogen bonding interaction between [EtOHim][NTf2] and NH3. This work not only demonstrate that the introduction of ILs is beneficial for improving NH3 separation performance of membranes but also emphasize the importance of moderate interaction between ILs and NH3 molecules for containing-NH3 separation.

Electron collision with Ammonia and phosphine at wide range of energies

The NH3 and PH3 molecules achieve differential electron elastic scattering cross-sections for energies ranging from 15 eV to 500 eV for ammonia and from 5 to 500 eV for phosphine. Calculations are performed using partial waveforms describing the target molecule using a single Hartree-Fock Molecular Function Center. The potentials used include a constant part—numerically obtained from quantum computation in addition to subtle effects such as correlation, polarization, and potential exchange, results of this model clearly show the role of the exchange, as well as the contributions of correlation and polarization, especially at low scattering angles and incident energies. The differential cross-sections obtained were compared with a large amount of experimental data from the research, and good agreement was found. Throughout the scattering angles and power ranges examined here. http://dx.doi.org/10.31257/2018/JKP/2022/140208

Luminescence Measurements of the Hyperthermal Reactions of N/N+ + NH3.

Chemiluminescence from a system of collisions, N+/N/Kr+/Kr/Xe+/Xe + NH3, at collision energies between 10 and 170 eV (center of mass, COM), was measured in the spectral range 300-1000 nm. The energy dependence of the emission excitation cross sections was quantified, and molecular signatures were fit to known spectroscopic constants to determine vibrational-state populations. For both N and N+ collision species, the strongest features were assigned to emissions from NH (A-X) and the atomic hydrogen Balmer series. For each of the spectra resulting from collisions with primary cations, the NH (A-X) emissions had the largest cross sections reaching values of (1.0-1.5) × 10-18 cm2 by 100 eV. Additional features originating from atomic nitrogen and NH (c-a) emissions were also observed. The NH (c-a) emissions accounted for about 8%, 13%, and 15% for total excited populations in collisions with Xe+, N+, and Kr+, respectively. These transitions were consistent with short-range interactions resulting in collision-induced dissociation of the NH3 molecule with apparent energy thresholds between 20 and 30 eV and emission cross sections decreasing with ion mass. Evidence of charge exchange in the N+ + NH3 collisions was observed in the resulting spectra as broad transitions between 420 and 480 nm and were assigned to NH+ emitting from the (B) state. Differences between the spectra were observed as changes in the emission signal with the neutral collisions producing only 30% or 65% of the NH (A-X) emission cross sections compared to the cation results for xenon and krypton, respectively. For N and N+, NH (A) was created in equal amounts at lower collision energies, but the emission for the neutral system increases above that of the cation at collision energies greater than 80 eV COM. In both cases, the threshold energy for appearance was below 10 eV, suggesting an additional pathway for NH (A) formation, namely, hydrogen abstraction or charge exchange and abstraction for the N and N+, respectively. In all cases, the neutral NH (c-a) emission intensity was similar between neutral and cation pairs. The H-α emission line (n = 3-2) decreased to about 10%, 33%, and 50% of the corresponding cation spectra for xenon, krypton, and nitrogen, respectively.

Redox-transitions in NO/NH3 adlayers on a Pt(111) electrode in an acidic solution

The process of electroreduction of nitrate anions is of considerable interest for researchers both as a fundamental (investigation of a multistage reaction, properties of intermediate products) and practical (water treatment) problem. A key intermediate product of nitrate anion electroreduction is nitric oxide NO that occupies two different types of sites on the Pt(111) surface: atop and 3-fold hollow. This paper studies redox transitions of N-containing species in the adsorption layer on Pt(111) in a wide range of potentials in a nitrate solution and in a preadsorbed saturated NO layer after its partial reduction in a negatively going potential sweep. Such partial reduction results in the appearance of a stable reversible pair of peaks in voltammograms at 0.6 V RHE. Analysis of charge densities of partial NO reduction and of this redox process shows that this pair of peaks corresponds to a one–electron redox transition between NH3(ads) and NH2(ads). We suggest a scheme based on the obtained results and literature data that explains the voltammetric signals observed in a wide range of potentials on an adsorption layer on Pt(111) formed by partial reduction of full NO adlayer. In this scheme, NH3(ads) molecules are formed in reduction of atop-bound NO and do not desorb from the surface owing to formation of coadsorption complexes with unreduced hollow-bound NO molecules. Such complexes are quite stable up to the potentials of hollow-bound NO reduction. In the potential range around 0.6 V, NH3(ads) molecules in such complexes are reversibly oxidized to NH2(ads) species that do not desorb either and remain within the coadsorption lattice. Moreover, the obtained NO/NH2(ads) is so stable that it suppresses oxidation of unreduced hollow-bound NO molecules in this complex to nitrite species.

Constructing Efficient Nickel Catalysts on CeOx Nanoparticles Stabilized Using γ-Al2O3 to Catalyze Ammonia Decomposition for Hydrogen Production

Highly efficient oxide–metal interfaces in solid catalysts play a crucial role in numerous heterogeneous catalysis applications. In this work, an active and stable interface is fabricated between Ni and CeO2 nanoparticles, which are stabilized using an Al2O3 support, and it enormously boosts the catalytic performance for the NH3 decomposition reaction. Systematic characterizations demonstrate that the small CeO2 nanoparticles on the Al2O3 support optimize the dispersion of Ni nanoparticles and modulate the reducibility of the interfacial Ni atoms, which directly correlate with the enhancement of the catalytic reactivity and stability. Moreover, in situ Raman and TPR results illustrate that the abundant surface-defective structure over small CeO2 nanoparticles augments the adsorption and activation sites of NH3 molecules for the Ni-CeOx/Al2O3 catalyst. This work deepens the understanding of the synergistic effect between active metal and oxides and provides a facile strategy for designing efficient NH3 decomposition catalysts.

Ammonia Capture in Rhodium(II)-Based Metal-Organic Polyhedra via Synergistic Coordinative and H-Bonding Interactions.

Ammonia (NH3) is among the world's most widely produced bulk chemicals, given its extensive use in diverse sectors such as agriculture; however, it poses environmental and health risks at low concentrations. Therefore, there is a need for developing new technologies and materials to capture and store ammonia safely. Herein, we report for the first time the use of metal-organic polyhedra (MOPs) as ammonia adsorbents. We evaluated three different rhodium-based MOPs: [Rh2(bdc)2]12 (where bdc is 1,3-benzene dicarboxylate); one functionalized with hydroxyl groups at its outer surface [Rh2(OH-bdc)2]12 (where OH-bdc is 5-hydroxy-1,3-benzene dicarboxylate); and one decorated with aliphatic alkoxide chains at its outer surface [Rh2(C12O-bdc)2]12 (where C12O-bdc is 5-dodecoxybenzene-1,3-benzene dicarboxylate). Ammonia-adsorption experiments revealed that all three Rh-MOPs strongly interact with ammonia, with uptake capacities exceeding 10 mmol/gMOP. Furthermore, computational and experimental data showed that the mechanism of the interaction between Rh-MOPs and ammonia proceeds through a first step of coordination of NH3 to the axial site of the Rh(II) paddlewheel cluster, which triggers the adsorption of additional NH3 molecules through H-bonding interaction. This unique mechanism creates H-bonded clusters of NH3 on each Rh(II) axial site, which accounts for the high NH3 uptake capacity of Rh-MOPs. Rh-MOPs can be regenerated through their immersion in acidic water, and upon activation, their ammonia uptake can be recovered for at least three cycles. Our findings demonstrate that MOPs can be used as porous hosts to capture corrosive molecules like ammonia, and that their surface functionalization can enhance the ammonia uptake performance.

Spectroscopic Determination of C, N, and O Abundances of Solar-analog Stars Based on the Lines of Hydride Molecules

Photospheric C, N, and O abundances of 118 solar-analog stars were determined by applying the synthetic-fitting analysis to their spectra in the blue or near-UV region comprising lines of CH, NH, and OH molecules, with an aim of clarifying the behaviors of these abundances in comparison with [Fe/H]. It turned out that, in the range of −0.6 ≲ [Fe/H] ≲ +0.3, [C/Fe] shows a marginally increasing tendency with decreasing [Fe/H] with a slight upturn around [Fe/H] ∼ 0, [N/Fe] tends to somewhat decrease toward lower [Fe/H], and [O/Fe] systematically increases (and thus [C/O] decreases) with a decrease in [Fe/H]. While these results are qualitatively consistent with previous determinations mostly based on atomic lines, the distribution centers of these [C/Fe], [N/Fe], and [O/Fe] at the near-solar metallicity are slightly negative by several hundredths of dex, which is interpreted as due to unusual solar abundances possibly related to the planetary formation of our solar system. However, clear anomalies are not observed in the [C, N, O/Fe] ratios of planet-host stars. Three out of four very Be-deficient stars were found to show anomalous [C/Fe] or [N/Fe] which may be due to mass transfer from the evolved companion, though its relation to the Be depletion mechanism is still unclear.

Cu-Doped MoSi2 N4 Monolayer as a Potential NH3 Sensor.

Cu doped MoSi2 N4 monolayer (Cu-MoSi2 N4 ) was firstly proposed to analyze adsorption performances of common gas molecules including O2 , N2 , CO, NO, NO2 , CO2 , SO2 , H2 O, NH3 and CH4 via density functional theory (DFT) combining with non-equilibrium Green's function (NEGF). The electronic transport calculations indicate that Cu-MoSi2 N4 monolayer has high sensitivity for CO, NO, NO2 and NH3 molecules. However, only NH3 molecule adsorbs on the Cu-MoSi2 N4 monolayer with moderate strength (-0.55 eV) and desorbs at room temperature (2.36×10-3 s). Thus, Cu-MoSi2 N4 monolayer is demonstrated as a potential NH3 sensor.

Enhanced selectivity and ultra-fast detection of NO2 gas sensor via Ag modified WO3 nanostructures for gas sensing applications

Recently, nanostructured tungsten oxide-based materials have received much attention in the field of the gas sensor due to their superior size-dependent gas adsorption and catalytic properties. Herewith, we have successfully prepared pure and Ag-doped WO3 nanostructures via a hydrothermal method. The effect of doping (Ag) in WO3 and their gas sensing properties was systematically studied. Interestingly, the Ag-2 sensor revealed the enhanced gas sensing response of 52404% @1000 ppb, which is 5-fold higher than that of the pure WO3 sample at 150 ℃. Moreover, Ag-2 sensor possessed an ultra-fast response and recovery time of 1 s and 3.5 s. Further, as-prepared sensors exhibit excellent selectivity, repeatability, and long-term stability. In addition, the DFT calculations were performed to evaluate the adsorption and charge transfer dynamics of NH3, H2S, and NO2 gas molecules on pure and Ag-doped WO3 surfaces. These results pave the new pathway to developing real-time metal oxide-based gas sensors at lower operating temperatures.

Porous multi-site ionic liquid composites for superior selective and reversible adsorption of ammonia

Ionic liquids (ILs) with low vapor pressure, tunable structures and good NH3 affinity provide an inspiring way to efficiently capture NH3. However, the high viscosity of most ILs limited mass transfer, which incumbers their industrial applications. Besides, how to simultaneously achieve high selectivity, capacity and reversibility of NH3 still face great challenge. Herein, four novel hydroxyl ammonium protic ILs (HAPILs), including methyldiethanolammonium trifluoromethanesulfonate ([MDEAH][CF3SO3]), triethanolammonium trifluoromethanesulfonate ([TEAH][CF3SO3]), dimethylethanolammonium trifluoromethanesulfonate ([DMEAH][CF3SO3]) and diethylethanolammonium trifluoromethanesulfonate ([DEEAH][CF3SO3]), with multiple hydrogen bonding donors that can interact with more over two NH3 molecules were designed and synthesized, and were further supported onto porous molecular sieves to overcome the above problem. Among the prepared porous HAPIL composites, 50 wt% [TEAH][CF3SO3]@MCM-41 showed the highest NH3/CO2 selectivity of 62 under 313 K and 0.1 MPa compared with the state-of-the-art values, along with high capacity of 114.3 mgNH3/g-adsorbent. The excellent NH3 adsorption performance was attributed to the synergistic interaction of mesoporous effect and multiple hydrogen bonding between NH3 and HAPILs. Furthermore, the porous HAPIL composites exhibited great recyclability after six cycles, revealing great potentials in industrial application of efficient and reversible NH3 separation.

Pristine and transition metal decorated holey graphyne monolayer as an ammonia sensor: insights from DFT simulations

The first-principles density functional theory method has been employed to comprehensively investigate adsorption configurations, adsorption energies, electronic properties, and gas sensing characteristics of pure and transition metal (TM = Sc, Pd, and Cu) decorated holey graphyne (HGY) monolayer for the detection of ammonia (NH3). The calculations reveal that the NH3 molecule weakly interacts with the pristine HGY surface with an adsorption energy of −0.146 eV. The expedited charge transfer and strong orbital hybridization between the NH3 molecule and the decorated TM (except Pd) resulted in the strong adsorption of the NH3 on the TM-decorated system. Among the three metals, it is found that the Sc decorated HGY can be regarded as the potential NH3 sensor owing to its reasonable adsorption energy of −1.49 eV, a large charge transfer of 0.113e, and an attainable recovery time of 3.2 s at 600 K. Furthermore, the stability of the Sc decorated HGY structure at ambient temperature is also validated using the ab initio molecular dynamic simulations. The results of the current study mirror the probable application of 2D HGY-based gas sensors for the detection of ammonia.

N2-to-NH3 conversion by excess electrons trapped in point vacancies on 5f-element dioxide surfaces.

Ammonia (NH3) is one of the basic chemicals in artificial fertilizers and a promising carbon-free energy storage carrier. Its industrial synthesis is typically realized via the Haber-Bosch process using traditional iron-based catalysts. Developing advanced catalysts that can reduce the N2 activation barrier and make NH3 synthesis more efficient is a long-term goal in the field. Most heterogeneous catalysts for N2-to-NH3 conversion are multicomponent systems with singly dispersed metal clusters on supporting materials to activate N2 and H2 molecules. Herein, we report single-component heterogeneous catalysts based on 5f actinide dioxide surfaces (ThO2 and UO2) with oxygen vacancies for N2-to-NH3 conversion. The reaction cycle we propose is enabled by a dual-site mechanism, where N2 and H2 can be activated at different vacancy sites on the same surface; NH3 is subsequently formed by H- migration on the surface via associative pathways. Oxygen vacancies recover to their initial states after the release of two molecules of NH3, making it possible for the catalytic cycle to continue. Our work demonstrates the catalytic activities of oxygen vacancies on 5f actinide dioxide surfaces for N2 activation, which may inspire the search for highly efficient, single-component catalysts that are easy to synthesize and control for NH3 conversion.

Highly sensitive and selective sensing-performance of 2D Co-decorated phthalocyanine toward NH3, SO2, H2S and CO molecules

Developing excellent sensing-materials for detecting and monitoring toxic gases in the air is significant for environmental monitoring and industrial emission evaluation. Herein, the first-principles calculations were employed to systematically investigate the adsorption characteristics of twelve different gas molecules (NH3, NO, NO2, SO2, H2S, CO, CO2, CH4, H2O, H2, O2, N2) on the two-dimensional phthalocyanine (Pc) and Co decorated phthalocyanine (CoPc), the electronic properties of various adsorption systems and their sensing-mechanism were also elucidated. The results show that the toxic NH3, NO, NO2, SO2, H2S are chemically adsorbed on the pristine Pc surface, whereas the poor sensitivity of Pc monolayer makes it not suitable to be a sensing-material. By contrast, the CoPc monolayer exhibits the appropriate adsorption strength toward the six poisonous gases (NH3, NO, NO2, SO2, H2S, CO), which is detailedly explained by the analysis of charge transfer, charge density difference and density of states. Moreover, the CoPc monolayer possesses high selectivity to those six gases even if it is in a humid environment. The CoPc monolayer also has excellent sensitivity for those toxic gases due to the obvious variations of bandgap, magnetic moment or work function. Additionally, the recovery time of NH3, SO2, H2S and CO is estimated to be about 3.91 min, 0.02 s, 24.19 ns and 226.38 ns at room temperature, respectively. Consequently, the CoPc monolayer based gas sensor has a great potential application for the NH3, SO2, H2S and CO detection.

Full-dimensional automated potential energy surface development and detailed dynamics for the CH2OO + NH3 reaction.

With the help of the ROBOSURFER program package, a global full-dimensional potential energy surface (PES) for the reaction of the Criegee intermediate, CH2OO, with the NH3 molecule is developed iteratively using different ab initio methods and the monomial symmetrization fitting approach. The final permutationally-invariant analytical PES is constructed based on 23447 geometries and the corresponding ManyHF-based CCSD(T)-F12b/cc-pVTZ-F12 energies. The accuracy of the PES is confirmed by the excellent agreement of its stationary-point properties and one-dimensional potential energy curves compared with the corresponding ab initio data. The reaction probabilities and integral cross sections are calculated for the ground-state and several vibrationally excited-state reactions by quasi-classical trajectory simulations. Remarkable is that the maximum impact parameter b where reactivity vanishes is almost independent of collision energy ranging from 1 to 40 kcal mol-1, and the reaction probability increases with increasing collision energy for this negative-barrier reaction. At the same time, a slight mode-specificity effect is observed. In addition, the deuterium effect is investigated and the sudden vector projection is discussed.

On the impact of adsorbed gas molecules on the anisotropic electro-optical properties of β12-borophene.

We theoretically study the role of adsorbed gas molecules on the electronic and optical properties of monolayer β12-borophene with {a,b,c,d,e} atoms in its unit cell. We focus our attention on molecules NH3, NO, NO2, and CO, which provide additional states permitted by the host electrons. Utilizing the six-band tight-binding model based on an inversion symmetry (between {a,e} and {b,d} atoms) and the Kubo formalism, we survey the anisotropic electronic dispersion and the optical multi-interband spectrum produced by molecule-boron coupling. We consider the highest possibilities for the position of molecules on the boron atoms. For molecules on {a,e} atoms, the inherent metallic phase of β12-borophene becomes electron-doped semiconducting, while for molecules on {b,d} and c atoms, the metallic phase remains unchanged. For molecules on {a,e} and {b,d} atoms, we observe a redshift (blueshift) optical spectrum for longitudinal/transverse (Hall) component, while for molecules on c atoms, we find a redshift (blueshift) optical spectrum for longitudinal (transverse/Hall) component. We expect that this study provides useful information for engineering field-effect transistor-based gas sensors.

Synthesis and study of the agrochemical properties of urea salts with nitric and orthophosphoric acid

The paper presents the results of the synthesis, IR spectroscopic and agrochemical study of the products of adduct formation (internal salts) of urea with nitric and orthophosphoric acids. It has been established that the synthesized substances are hygroscopic, readily soluble in water. IR spectral data indicate that, depending on the “acid : urea” ratio in the final products CO, NH2, urea groups and acid molecules are involved in the formation of various compositions: [H2O···(NH2)2C(OH)+···-ONO2] and [O2N-O-···+H3N(H2N)C(OH)+···-O-NO2], [-NH3+···-O-P(O)(OH)2] and [C(OH)+···-O-P(O)(OH)2] salt bridges. The solubility of poorly soluble salts, which are included in a series of metal ion compounds accumulating in the soil under the action of urea mononitrate, has been studied. According to the results of an agrochemical study of the effect of synthesized urea salts on the digestibility of P2O5 by Tr-B and citric acid in the soil, an increase in these parameters under the action of urea dinitrate and diorthophosphate was found to be within 8.26–11.52 and 8.28–9.52%, relative to control 1.07 and 0.787%, respectively.

Study on the mechanism of NOx reduction by NH3-SCR over a ZnXCu1-XFe2O4 catalyst.

Experimental evidence shows that CuFe2O4 exhibits excellent catalytic performance in the SCR reaction. However, there is a lack of in-depth research on its specific reaction mechanism. Our study begins by computing the adsorption model of molecules like NH3 and then goes on to examine the SCR reaction mechanism of NH3 on CuFe2O4 before and after Zn doping. The results indicate that NH3 is chemically adsorbed (-1.26 eV) on the surface and has a strong interaction with the substrate. Importantly, Zn doping provides more favorable reactive sites for NH3 molecules. Subsequent investigation into the NH3 dehydrogenation and SCR reaction processes showed that incorporating Zn can greatly decrease the energy barrier of the most critical step in the reaction (0.58 eV). Additionally, the study also assesses the feasibility of the reaction of adsorbed NO with surface active O atoms to form NO2 (barrier 0.86 eV). Lastly, the sulfur resistance of the catalyst before and after doping is calculated and analyzed, and it is found that Zn doping effectively improves the sulfur resistance. Our study provides valuable theoretical guidance for the development of ferrite spinel and doping modification.

Phosphorus doping of graphene for conductometric room temperature ammonia sensing

The ammonia (NH3)-sensing performance of phosphorus-doped graphene sensors is systematically investigated in this paper. Using a chemical vapor deposition (CVD) system, phosphorus pentoxide was used as the phosphorus source to achieve stable phosphorus doping of graphene at 480 oC. The NH3-sensing test results showed that the NH3 response of phosphorus-doped graphene increased by 2.4 times on average, the response (recovery) time shortened by 70.6% (73.4%) on average, and the theoretical limit of detection (LOD) was 68.76 ppb. In addition, the phosphorus-doped graphene sensor also exhibits excellent repeatability, stability, and ultra-high selectivity to NH3. XPS, EDS, and FTIR analysis show that the P-O groups introduced on graphene are the key to improving the NH3 sensitivity of graphene. The P-O groups provide sufficient O atoms to assist graphene to adsorb NH3 molecules, thereby improving the NH3 sensitivity of graphene. A simple, large-scale implementable, and effective phosphorus doping by the CVD method was proposed to improve the NH3 sensitivity of graphene in this work, which is of great significance for promoting the practical application of graphene gas sensors.