NH3 Treatment Research Articles

Characterization and photocatalytic activity of titanium dioxide powder treated with PH3 gas

NH3 treatment for nitrogen doping to metal oxides is widely used as a method of band gap narrowing. However, PH3 treatment of titanium dioxide(TiO2) powders has not yet been established. In the present study, PH3 treatment of TiO2 was attempted by heating TiO2 powders and solid-state sodium hypophosphite in a sealed ampoule. The color of the powders changed from colorless for untreated TiO2 to beige for TiO2 treated at 250, 290, 350 °C, or to gray for TiO2 treated at 450 °C. X-ray photoelectron spectroscopy (XPS) analysis of the treated TiO2 revealed that the phosphorus was in a phosphate form and that a part of Ti4+ in TiO2 was reduced to Ti3+. The absorption spectra and the XPS data suggested the generation of oxygen vacancies. Adsorption experiments of methylene blue and Eosin Y onto the treated TiO2 indicated the presence of phosphate on the surface of TiO2. X-ray diffraction (XRD) analysis indicated that the crystallite sizes of the treated TiO2 increased with increasing in temperature. Photodegradation rates of the pigments by the treated TiO2 under UV light depended on phosphate, oxygen vacancy and crystallinity. PH3 treatment of crystalline TiO2 were found to give priority to phosphate formation in contrast to NH3 treatment for nitrogen doping.

DEVELOPMENT OF BIOFILM ON POLYURETHANE FOAM AND ITS APPLICATION IN A BIO-TRICKLING FILTER FOR TREATMENT OF ODOR FROM DOMESTIC SOLID WASTE

This study investigates the ability of a self-fabricated bio-trickling filter using commercial polyurethane foam as bio-media for treatment of odor-causing gases (e.g., ammonia, hydrogen sulfide, and mercaptans) under different nitrogen loadings in gas and liquid phases. The experimental results showed that the biological filter operating with a gas flow rate of 11.44 m3/h and an empty bed residential time of 19.67 s could treat the multi-components emitted from domestic solid waste. Ammonia treatment efficiency was achieved in the range of 87.3 to 99.7% with the highest ammonia input concentration of l47.3 mg/m3. The efficiency of mercaptans treatment was from 60.2 to 72.8% with an input concentration of about 8 mg/m3 while the low input and output concentrations of hydrogen sulfide were found (≤ 0.002 mg/m3). Besides, there was a significant difference between elimination capacity of NH3-N (gas phase) and accumulated capacity of NH4+-N and NO3--N (liquid phase) although the ammonia treatment efficiency was very high, which could be attributed to the denitrification process. The results from this study hence suggest using bio-trickling filter for effective treatment of NH3 and other odor in gas generated from domestic solid waste.

Impacts of surface nitridation on crystalline ferroelectric phase of Hf1-xZrxO2 and ferroelectric FET performance

This paper presents an approach to enhance Hf0.5Zr0.5O2 (HZO) ferroelectric orthorhombic phase (O-phase) formation via in situ NH3 plasma treatment. High-resolution non-disruptive hard x-ray photoelectron spectroscopy confirmed that O-phase formation can be enhanced by suppressed interfacial diffusion between HZO and the top TiN electrode. Additional N-bonding facilitated by NH3 treatment was shown to suppress the interaction between TiN and HZO, thereby reducing the formation of oxygen vacancies within HZO. It was shown to improve the reliability and ferroelectric performance (examined by the leakage current and positive-up-negative-down measurements) of HZO devices. After cyclic operations, NH3-treated ferroelectric FETs (FeFETs) exhibited stable transfer characteristics and memory windows, whereas untreated devices presented unstable behaviors. Our results demonstrate the efficacy of the proposed in situ NH3-treatment scheme in enhancing the stability of HZO-based FeFETs.

Solid phase characterization and transformation of illite mineral with gas-phase ammonia treatment

In situ remediation applications of ammonia (NH3) gas have potential for sequestration of subsurface contamination. Ammonia gas injections initially increase the pore water pH leading to mineral dissolution followed by formation of secondary precipitates as the pH is neutralized. However, there is a lack of understanding of fundamental alteration processes due to NH3 treatment. In these batch studies, phyllosilicate minerals (illite and montmorillonite) were exposed to NH3 gas with subsequent aeration to simulate in situ remediation. Following treatments, solids were characterized using a variety of techniques, including X-ray diffraction, N2 adsorption-desorption analysis for surface area, Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), and microscopy methods to investigate physicochemical transformations. Results indicate that, at high pH, the clays are altered as observed by differences in morphology and particle size via microscopy. However, the two clays interact differently with NH3. While montmorillonite interlayers collapsed due to intercalation, illite layers were unaffected as confirmed by FTIR analysis. Further, structural changes in silicate ([SiO4]n-) and aluminol (Al-OH) groups were identified by NMR and FTIR. This research showed that mineral alteration processes occur during and after NH3 gas treatment which may be used to remove radionuclides from the aqueous phase through sorption, co-precipitation, and coating with secondary phyllosilicate alteration products.

Effects of surface treatments on flux tunable transmon qubits

One of the main limitations in state-of-the art solid-state quantum processors is qubit decoherence and relaxation due to noise from adsorbates on surfaces, impurities at interfaces, and material defects. For the field to advance towards full fault-tolerant quantum computing, a better understanding of these microscopic noise sources is therefore needed. Here, we use an ultra-high vacuum package to study the impact of vacuum loading, UV-light exposure, and ion irradiation treatments on relaxation and coherence times, as well as slow parameter fluctuations of flux tunable superconducting transmon qubits. The treatments studied do not significantly impact the relaxation rate Γ1 and the echo decay rate {{{Gamma }}}_{2,{{{rm{SS}}}}}^{{{{rm{e}}}}} at the sweet spot, except for Ne ion bombardment which reduces Γ1. In contrast, flux noise parameters are improved by removing magnetic adsorbates from the chip surfaces with UV-light and NH3 treatments. Additionally, we demonstrate that SF6 ion bombardment can be used to adjust qubit frequencies in situ and post-fabrication without affecting qubit relaxation and coherence times at the sweet spot.

Effect of oxygen vacancies on improving NO oxidation over CeO2 {111} and {100} facets for fast SCR reaction

Different exposed crystal surface CeO2 catalysts (nanopolyhedrons and nanocubes) are synthesized and treated by NH3 to investigate the effect of oxygen vacancies on improving NO oxidation for fast SCR reaction. The experiment results show that N-CeO2-NPs catalyst (treated by NH3) has the most oxygen vacancies of the four catalysts, thus leading to the best oxidation activity of NO, which further promotes the fast SCR reaction. From the XPS and Raman spectra results, it indicates that the more oxygen vacancies are due to the higher concentration of Ce3+ and surface adsorbed oxygen resulting from the NH3 treatment at high temperature. Meanwhile, the test of NO conversion to NO2 shows that the rich oxygen vacancies promote the conversion of NO to NO2, in which N-CeO2-NPs catalyst yields more remarkable promotion of NO oxidation to NO2, respectively. Also, the magnitude of the variety is in accordance with that of the oxygen vacancy content and concentration of Ce3+ ions. Thus, CeO2 with NH3 treatment is found to significantly enhance its NH3-SCR performance which leads to higher NOx removal efficiency of N-CeO2-NPs catalyst with {111} exposed crystal surface.

Selenomethionine protects against ammonia-induced apoptosis through inhibition of endoplasmic reticulum stress in pig kidneys

Ammonia (NH3) emission is a common threat to farm animals. Selenium (Se) is known for its antioxidant property and can resist several stressors affecting farm animals. The aims of this study were (Ⅰ) to determine how excess NH3 exert nephrotoxic effects in pigs and (Ⅱ) to investigate whether selenomethionine has an alleviative effect on NH3 toxicity. Two diets supplemented with different doses of Se (0.22 mg/kg or 0.50 mg/kg) and two concentrations of NH3 (< 5 mg/m3 or 89.8 mg/m3) were used in a 2 × 2 factorial design trial for a period of 30 days. The results showed that NH3 exposure caused apoptosis and increased the number of apoptotic cells in pig kidneys. Further, the activities of antioxidant enzymes were decreased, and the transcriptional and translational levels of endoplasmic reticulum stress-related genes, Bcl-2 and Caspase family members were increased under NH3 exposure. In addition, Wnt/β-catenin signaling pathway was suppressed after NH3 treatment. Dietary supplement with selenomethionine appears to offer protection against NH3-induced kidney injury in pigs and the pathologic changes above were alleviated. Our findings provide additional insight into the mechanism of NH3 toxicity in pigs while elucidating the role of Se as a potential antidote against NH3 poisoning.

N-Doped Biochar as H2s Adsorbent for the Biogas-Fueled SOFC

Reliability of biogas-fueled SOFC is tied directly to the purity of biogas used as fuel. Even miniscule amount of H2S can poison the anode material and drastically shorten the operation time of biogas-fueled SOFC. In order to prevent the performance degradation caused by H2S poisoning, the aim of this study is to develop an attractive process to obtain a nitrogen (N)-doped carbon derived from biomass feedstock using the digested liquid as a source of N, which can act as an excellent adsorbent material to reduce the H2S concentration in biogas below sub ppm level.Rice husk (RH) was pyrolyzed at 500oC for 2 h under O2-free atmosphere to produce biochar (BC). Rice husk biochar (RH-BC) was then treated with ammonia gas (25% NH3) at 500 or 900°C for 2 h (Intense N-doping) to have N-doped RH-BC (RH-BC(N500-120) and RH-BC(N900-120)). 10% NH3 solution was prepared to simulate the concentrated ammonia solution obtained from the digested liquid discharged from the methane fermentation reactor. The 10% NH3 solution was heated at 30oC through which 100 mL min-1 N2 was passed to obtain the vaporized NH3. RH-BC was treated with the NH3 vapor at 850°C for 90 or 270 min (Mild N-doping) to have N-doped RH-BC (RH-BC(EN850-90) and RH-BC(EN850-270)). Aiming at increasing the total H2S adsorption capacity (ACPH2S ), prior to the mild N-doping, pre-treatment of RH-BC with 15 vol% steam was performed at 850°C for 90 min (RH-BC(S850-90 + EN850-90)).Specific surface area (SSA) of the porous RH-BC was 146 m2 g-1. By the NH3 treatment of the RH-BC, pyridinic-like N can be doped on the surface contributing to the formation of the oxygen radicals to consume H2S, leading to the enhancement of the ACPH2S . RH-BC(N900-120) exhibited the highest breakthrough capacity (APCH2S(0) ) of 8.02 mg H2S g-BC-1 and ACPH2S of 9.58 mg H2S g-BC-1. However, the highest ACPH2S , 25.6 mg H2S g-BC-1, was obtained for RH-BC(S850-90 + EN850-90), while its APCH2S(0) was 3.64 mg H2S g-BC-1.XPS analysis revealed that, during the H2S adsorption, intense N-doping (RH-BC(N900-120)) resulted in the larger amount of sulfate formation on the surface compared to the mild N-doping (RH-BC(S850-90 + EN850-90)). Abundance of oxygen radicals on the surface is preferable for the sulfate formation. This explains the high ACPH2S(0) of the intensely N-doped sample, RH-BC(N900-120). On the other hand, for the mildly N-doped sample, RH-BC(S850-90 + EN850-90), interaction of the surface with H2S was moderately weakened to avoid the blocking of the micropore openings with sulfate, which enables the H2S molecules to adsorb into the micropores, resulting in the higher ACPH2S .

Life Cycle Assessment of Nitrogen Circular Economy-Based NOx Treatment Technology

Humans are significantly perturbing the global nitrogen cycle, leading to excess reactive nitrogen in the environment. Nitrogen oxides as a key reactive nitrogen species are mainly controlled by selective non-catalytic reduction and selective catalytic reduction. Converting nitrogen oxides to ammonia, defined as ReNOx, emerges as an alternative method under a disparate design concept. However, little is known about its overall environmental performance. In this study, we conducted for the first time a life cycle assessment of ReNOx. Compared with the eco-index in the condition of 200 °C with a conversion rate of 95%, it would increase substantially in the condition of 160 °C with a conversion rate of 80% and in the case without a sound NH3 treatment. Feedstock format change, adsorption material performance deterioration, and recovery rate decline would increase the eco-index by 8%, 12%, and 18%, respectively. The eco-index was decreased by 31% in the optimized scenario with a renewable energy source and an increased conversion rate. The environmental impacts were compared with traditional methods at impact, damage, and eco-index levels. Finally, the implications on process arrangement in the flue gas system, the externality for power generation, and the contribution to the nitrogen circular economy were examined. The results can serve as a reference for its developers to improve the technology from the environmental perspective.

NH3 treatment of CeO2 nanorods catalyst for improving NH3-SCR of NO

CeO2 nanorods (CeO2-NRs) catalyst was prepared and treated with ammonia (NH3) gas and the effect of NH3 treatment on CeO2 nanorods catalyst was also studied for improving NH3-SCR of NO. And the catalysts were tested for NH3-SCR of NO during 100–450 °C. The results showed that NH3 treatment could improve the De-NO efficiency of the catalyst, which increased evidently in the range of about 160–410 °C. XPS results revealed that NH3 treatment made CeO2-NRs catalyst produce more Ce3+ on its surface, and thereby produced more oxygen vacancies and further promoted SCR reaction. The XRD and H2-TPR characterization test results indicated that CeO2 catalyst with NH3 treatment could destroy its crystallinity and enhance the reducibility. In addition, the in situ DRIFTS results also exhibited more activity functional groups on the surface of N–CeO2-NRs catalyst than that of CeO2-NRs catalyst.

Catalytic oxidation of NO at low concentrations by carbon nanofibers near room temperature

Polyacrylonitrile (PAN) nanofibers obtained by electrospinning were used to prepare PAN-based carbon nanofibers (PCNFs) by pre-oxidation, carbonization and high-temperature treatment in NH3. The PCNFs were used for the removal of low concentrations of NO (5×10−5) near room temperature (20 °C) by catalytic oxidation. Results indicated that the PCNFs had high porosity and a large specific surface area, and their diameters could be regulated by changing the PAN concentration. The smaller the diameter of the PCNFs the more micropores were developed, and the larger the specific surface area the better the adsorption and catalytic oxidation performance.

Ship-in-a-Bottle Synthesis of High Concentration of N2 Molecules in a Cage-Structured Electride.

We report the formation of neutral nitrogen molecules in the cages of [Ca12Al14O32]2+ (C12A7) framework compensated by extra-framework anions. NH3 treatment of C12A7 electride (C12A7:e-) at 800 °C leads to the formation of N2 and NH2- species in the C12A7 cages. N2 and NHx species in the cages are identified using the Raman spectroscopy of 14NH3 and 15NH3-treated C12A7:e-. The concentration of H and N in the C12A7 cages after NH3 treatment is ∼1021 cm-3. We propose a two-step mechanism, supported by density functional theory (DFT) modeling, of N2 incorporation into the C12A7 cages, i.e., incorporation of NH2- formed from decomposition of NH3 at C12A7:e- surface followed by the NH2- species reacting to form N2 molecules. Encapsulation of neutral molecules, as opposed to negatively charged species reported in C12A7 previously, offers new opportunities for trapping and storing gaseous substances in nanoporous materials.

Fabrication of Controllable N-Doped Ce0.2Zr0.8O2 via O–N–O Bond with Robust NO Oxidation and Durability at Low Temperature

N-doped Ce0.2Zr0.8O2 catalysts for NO oxidation were successfully fabricated via NH3 treatment at high temperature, and the N doping amount could be controlled via adjusting the conditions of various NH3 concentrations and treatment times. The optimal 10N700-5 catalyst revealed the sensational oxidation efficiency at low temperature, which surpassed 50% at 180 °C and reached up to 82.82% at 270 °C. The excellent activity was ascribed to the numerous generations of O2– and the accompanied vast formation of Cr6+, caused by N doping. N atoms were doped in Ce0.2Zr0.8O2 in the structure of Ce–O–N–O–Zr via the O–N–O bond between N and O. The analysis of affecting factors elucidated that cation ratios played a more significant role than the Brunauer–Emmett–Teller surface area, and Cr6+ ratios acted mostly. Additionally, the conceivable promotion mechanism by N doping for NO oxidation was examined via in situ DRIFTS. This work propelled denitration with the selective catalytic oxidation technique for industrial application and lent a novel perspective for the design of catalysts with satisfied oxidation efficiency at low temperature.

Atomic Sandwiched p‐n Homojunctions

AbstractSemiconductor p‐n junctions have been explored and applied in photoelectrochemical (PEC) water splitting, but serious carrier recombination and sluggish oxygen evolution reaction (OER) dynamics have demanded further progress in p‐n junction photoelectrode design. Here, via a controllable NH3 treatment, we construct sandwiched p‐n homojunctions in three‐unit‐cells n‐type SnS2 (n‐SnS2) nanosheet arrays using nitrogen (N) as acceptor dopants. The optimal N‐doped n‐SnS2 (pnp‐SnS2) with such unique structure achieves a record photocurrent density of 3.28 mA cm−2, which is 21 times as high as that of n‐SnS2 and the highest value among all the SnS2 photoanodes reported so far. Moreover, the stoichiometric O2 and H2 evolution from water was achieved with Faradaic efficiencies close to 100 %. The superior performance could be attributed to the facilitated electron–hole separation/transfer, accelerated surface OER kinetics, prolonged carrier lifetime, and improved structural stability.

Atomic Sandwiched p-n Homojunctions.

Semiconductor p-n junctions have been explored and applied in photoelectrochemical (PEC) water splitting, but serious carrier recombination and sluggish oxygen evolution reaction (OER) dynamics have demanded further progress in p-n junction photoelectrode design. Here, via a controllable NH3 treatment, we construct sandwiched p-n homojunctions in three-unit-cells n-type SnS2 (n-SnS2 ) nanosheet arrays using nitrogen (N) as acceptor dopants. The optimal N-doped n-SnS2 (pnp-SnS2 ) with such unique structure achieves a record photocurrent density of 3.28 mA cm-2 , which is 21 times as high as that of n-SnS2 and the highest value among all the SnS2 photoanodes reported so far. Moreover, the stoichiometric O2 and H2 evolution from water was achieved with Faradaic efficiencies close to 100 %. The superior performance could be attributed to the facilitated electron-hole separation/transfer, accelerated surface OER kinetics, prolonged carrier lifetime, and improved structural stability.

Kinetic-model-based design of industrial reactor for catalytic hydrogen production via ammonia decomposition

A two-dimensional reactor model based on reaction kinetics and heat and mass transfer for catalytic NH3 decomposition was constructed. A reactor design that minimizes the effect of endothermic reaction was investigated. It is difficult to design a single-tube reactor for NH3 treatment at a flow rate of 10 m3/h because heat transfer from the reactor wall cannot keep up with the fast consumption of heat by the reaction, even under low space velocity conditions. The target conversion was achieved by decreasing the NH3 supply rate. A reactor with a packed bed of suitable length was designed. Industrial-scale NH3 treatment can be achieved using a multi-tube reactor.

Porous nitrogen-enriched hollow carbon nanofibers as freestanding electrode for enhanced lithium storage

One-dimensional porous carbons bearing high surface areas and sufficient heteroatom doped functionalities are essential for advanced electrochemical energy storage devices, especially for developing freestanding film electrodes. Here we develop a porous, nitrogen-enriched, freestanding hollow carbon nanofiber (PN-FHCF) electrode material via filtration of polypyrrole (PPy) hollow nanofibers formed by in situ self-degraded template-assisted strategy, followed by NH3-assisted carbonization. The PN-FHCF retains the freestanding film morphology that is composed of three-dimensional networks from the entanglement of 1D nanofiber and delivers 3.7-fold increase in specific surface area (592 m2·g−1) compared to the carbon without NH3 treatment (FHCF). In spite of the enhanced specific surface area, PN-FHCF still exhibits comparable high content of surface N functionalities (8.8%, atom fraction) to FHCF. Such developed hierarchical porous structure without sacrificing N doping functionalities together enables the achievement of high capacity, high-rate property and good cycling stability when applied as self-supporting anode in lithium-ion batteries, superior to those of FHCF without NH3 treatment.

Air oxidation coupling NH3 treatment of biomass derived hierarchical porous biochar for enhanced toluene removal

In this study, hierarchical porous biochar was prepared from poplar sawdust by air oxidation coupling with NH3 treatment for the removal of toluene. The results showed that the mesopore volume of the sample with air oxidation (PS‒O2) increased significantly to 0.263 cm3/g from the blank sample (PS, 0.053 cm3/g). This could be attributed to the selective removal of the lignin carbon by air oxidation to develop mesopores in biochar. Following further NH3 treatment (PS‒O2‒NH3), the basic surface chemistry on biochar was improved due to increased basic N-containing groups and decreased acidic O-containing groups, together with the micropore volume also increased to 0.231 cm3/g from 0.186 cm3/g of PS‒O2. The formation mechanism of hierarchical porous structure of biochar was also discussed. The adsorption capacity of PS‒O2‒NH3 for toluene reached 218.4 mg/g at the initial concentration of 820 mg/m3, which was 383.2% higher than that of PS. The adsorption isotherm study indicated that the adsorption process of toluene was monolayered and the maximal adsorption capacity of PS‒O2‒NH3 for toluene could reach as high as 476.2 mg/g. The results demonstrated that air oxidation coupling NH3 treatment is a highly effective method for the preparation of hierarchical porous biochar for enhancing toluene adsorption performance.

Turning poison into medicine: NH3 or urea treatment leads to improved Pd-based three-way catalysts

Contrary to the stereotype that exposure to NH3 or urea should be strictly avoided when preparing three-way catalysts using Pd due to Pd2+-NH3 coordination, remarkable catalytic activity improvement was realized with careful NH3 or urea treatment towards the oxides support or Pd precursor. And with the help of a newly designed facile CO temperature-programmed reduction (TPR) method, developed to replace traditional H2-TPR, it was found that the catalytic activity is closely related with the catalyst reducibility and total oxygen storage capacity (OSC, represented by the integrated area of a CO-TPR curve), thus showing the potential of this CO-TPR method for screening candidate catalysts. When applying the most effective “Urea-PP” technology during monolith converter preparation, this method could no longer show its advantage, unless an outer layer was coated to protect the highly active but also highly sensitive inner layer.

Oxidative stress and mitochondrial dysfunction involved in ammonia-induced nephrocyte necroptosis in chickens

Ammonia (NH3), an environmental pollutant, poses a serious threat to human and avian health. Although previous studies have showed that NH3 caused kidney injury, the molecular mechanisms of nephrotoxicity induced by NH3 remain unclear. To explore the mechanisms of NH3 nephrotoxicity, a total of 36 broiler chicks at one day of age were exposed to NH3. After 42 days of exposure, blood samples were collected to determine creatinine and uric acid; and kidney samples were weighted and then collected to detect ultrastructural changes, oxidative stress parameters, ATPases, necroptosis- and mitochondrial dynamics-related genes. The results showed that chickens exposed to NH3 showed lower relative kidney weight and an increase concentration in serum creatinine and uric acid. NH3 exposure caused nephrocyte necrosis and increased the expression of necroptosis-related genes (TNF-α, RIPK1, RIPK3, MLKL, and JNK). Besides, the activities of antioxidant systems (SOD, CAT, GSH-Px, and T-AOC) were reduced, whereas the concentrations of H2O2 and MDA were elevated. Lower activities of ATPases were obtained in NH3 treatment groups. Furthermore, the mitochondrial fission-related genes drp1 and mff were activated, and mitochondrial fusion-related genes opa1, mfn1 and mfn2 were suppressed after NH3 exposure. Based on the above results, we conclude that NH3 caused-oxidative stress and mitochondrial dysfunction mediated nephrocyte necroptosis in chickens. This study may provide new insight into NH3 nephrotoxicity.