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1.
Guike Zhang Xiaotian Li Kai Chen Yali Guo Prof. Dongwei Ma Prof. Ke Chu 《Angewandte Chemie (International ed. in English)》2023,62(13):e202300054
We demonstrate the great feasibility of MBenes as a new class of tandem catalysts for electrocatalytic nitrate reduction to ammonia (NO3RR). As a proof of concept, FeB2 is first employed as a model MBene catalyst for the NO3RR, showing a maximum NH3-Faradaic efficiency of 96.8 % with a corresponding NH3 yield of 25.5 mg h−1 cm−2 at −0.6 V vs. RHE. Mechanistic studies reveal that the exceptional NO3RR activity of FeB2 arises from the tandem catalysis mechanism, that is, B sites activate NO3− to form intermediates, while Fe sites dissociate H2O and increase *H supply on B sites to promote the intermediate hydrogenation and enhance the NO3−-to-NH3 conversion. 相似文献
2.
Enhancing Electrochemical Nitrate Reduction to Ammonia over Cu Nanosheets via Facet Tandem Catalysis
Yunfan Fu Shuo Wang Yi Wang Pengfei Wei Jiaqi Shao Dr. Tianfu Liu Prof. Dr. Guoxiong Wang Prof. Dr. Xinhe Bao 《Angewandte Chemie (International ed. in English)》2023,62(26):e202303327
Electrochemical conversion of nitrate (NO3−) into ammonia (NH3) represents a potential way for achieving carbon-free NH3 production while balancing the nitrogen cycle. Herein we report a high-performance Cu nanosheets catalyst which delivers a NH3 partial current density of 665 mA cm−2 and NH3 yield rate of 1.41 mmol h−1 cm−2 in a flow cell at −0.59 V vs. reversible hydrogen electrode. The catalyst showed a high stability for 700 h with NH3 Faradaic efficiency of ≈88 % at 365 mA cm−2. In situ spectroscopy results verify that Cu nanosheets are in situ derived from the as-prepared CuO nanosheets under electrochemical NO3− reduction reaction conditions. Electrochemical measurements and density functional theory calculations indicate that the high performance is attributed to the tandem interaction of Cu(100) and Cu(111) facets. The NO2− generated on the Cu(100) facets is subsequently hydrogenated on the Cu(111) facets, thus the tandem catalysis promotes the crucial hydrogenation of *NO to *NOH for NH3 production. 相似文献
3.
Yongguang Bu Chao Wang Wenkai Zhang Xiaohan Yang Jie Ding Prof. Guandao Gao 《Angewandte Chemie (International ed. in English)》2023,62(24):e202217337
Electrocatalytic nitrate reduction sustainably produces ammonia and alleviates water pollution, yet is still challenging due to the kinetic mismatch and hydrogen evolution competition. Cu/Cu2O heterojunction is proven effective to break the rate-determining NO3−-to-NO2− step for efficient NH3 conversion, while it is unstable due to electrochemical reconstruction. Here we report a programmable pulsed electrolysis strategy to achieve reliable Cu/Cu2O structure, where Cu is oxidized to CuO during oxidation pulse, then regenerating Cu/Cu2O upon reduction. Alloying with Ni further modulates hydrogen adsorption, which transfers from Ni/Ni(OH)2 to N-containing intermediates on Cu/Cu2O, promoting NH3 formation with a high NO3−-to-NH3 Faraday efficiency (88.0±1.6 %, pH 12) and NH3 yield rate (583.6±2.4 μmol cm−2 h−1) under optimal pulsed conditions. This work provides new insights to in situ electrochemically regulate catalysts for NO3−-to-NH3 conversion. 相似文献
4.
Jingwen Xu Shengbo Zhang Hengjie Liu Shuang Liu Yuan Yuan Yahan Meng Mingming Wang Chunyue Shen Qia Peng Jinghao Chen Xiaoyang Wang Prof. Li Song Prof. Ke Li Prof. Wei Chen 《Angewandte Chemie (International ed. in English)》2023,62(39):e202308044
The electrochemical conversion of nitrate pollutants into value-added ammonia is a feasible way to achieve artificial nitrogen cycle. However, the development of electrocatalytic nitrate-to-ammonia reduction reaction (NO3−RR) has been hampered by high overpotential and low Faradaic efficiency. Here we develop an iron single-atom catalyst coordinated with nitrogen and phosphorus on hollow carbon polyhedron (denoted as Fe−N/P−C) as a NO3−RR electrocatalyst. Owing to the tuning effect of phosphorus atoms on breaking local charge symmetry of the single-Fe-atom catalyst, it facilitates the adsorption of nitrate ions and enrichment of some key reaction intermediates during the NO3−RR process. The Fe−N/P−C catalyst exhibits 90.3 % ammonia Faradaic efficiency with a yield rate of 17980 μg h−1 mgcat−1, greatly outperforming the reported Fe-based catalysts. Furthermore, operando SR-FTIR spectroscopy measurements reveal the reaction pathway based on key intermediates observed under different applied potentials and reaction durations. Density functional theory calculations demonstrate that the optimized free energy of NO3−RR intermediates is ascribed to the asymmetric atomic interface configuration, which achieves the optimal electron density distribution. This work demonstrates the critical role of atomic-level precision modulation by heteroatom doping for the NO3−RR, providing an effective strategy for improving the catalytic performance of single atom catalysts in different electrochemical reactions. 相似文献
5.
《Analytical letters》2012,45(7):815-823
Abstract A sensitive spectrophotometric method, which directly measures the formation of pyruvic oxime from pyruvate and NH2OH in the UV, is described for the detection of pyruvic oxime hydrolase activity in biochemical systems. The method was used in an attempt to detect pyruvic oxime hydrolase activity in cell-free extracts from an Alcaligenes sp. which can grow on pyruvic oxime. Although substantial pyruvic oxime + nitrite oxidative activity was detected in cells and cell-free extract of this bacterium, catalysis of pyruvic oxime formation was not observed within the error of the method (~20% of the uncatalyzed rate constant of 1.9x10?3 s?1 at pH 7, 22°C). The rate of pyruvic oxime oxidation by cells and cell-free extract was at least 105?106 times greater than the rate of its hydrolysis, thus implying that oxidation of pyruvic oxime need not require prior hydrolysis. The method would appear to be applicable to hydrolases directed toward a variety of oximes. 相似文献
6.
Mengmiao Sun Guanzheng Wu Jiadi Jiang Yidong Yang Aijun Du Lei Dai Xin Mao Qing Qin 《Angewandte Chemie (International ed. in English)》2023,62(19):e202301957
The electrochemical NO3− reduction and its coupling with CO2 can provide novel and clean routes to synthesize NH3 and urea, respectively. However, their practical application is still impeded by the lack of efficient catalysts with desirable Faradaic efficiency (FE) and yield rate. Herein, we report the synthesis of molybdenum oxide nanoclusters anchored on carbon black (MoOx/C) as electrocatalyst. It affords an outstanding FE of 98.14 % and NH3 yield rate of 91.63 mg h−1 mgcat.−1 in NO3− reduction. Besides, the highest FE of 27.7 % with a maximum urea yield rate of 1431.5 μg h−1 mgcat.−1 toward urea is also achieved. The formation of electron-rich MoOx nanoclusters with highly unsaturated metal sites in the MoOx/C heterostructure is beneficial for enhanced catalytic performance. Studies on the mechanism reveal that the stabilization of *NO and *CO2NOOH intermediates are critical for the NH3 and urea synthesis, respectively. 相似文献
7.
Dr. Lun An Dr. Mina R. Narouz Dr. Peter T. Smith Patricia De La Torre Prof. Christopher J. Chang 《Angewandte Chemie (International ed. in English)》2023,62(35):e202305719
The electrochemical nitrate (NO3−) reduction reaction (NO3RR) to ammonia (NH3) represents a sustainable approach for denitrification to balance global nitrogen cycles and an alternative to traditional thermal Haber-Bosch processes. Here, we present a supramolecular strategy for promoting NH3 production in water from NO3RR by integrating two-dimensional (2D) molecular cobalt porphyrin ( CoTPP ) units into a three-dimensional (3D) porous organic cage architecture. The porphyrin box CoPB-C8 enhances electrochemical active site exposure, facilitates substrate–catalyst interactions, and improves catalyst stability, leading to turnover numbers and frequencies for NH3 production exceeding 200,000 and 56 s−1, respectively. These values represent a 15-fold increase in NO3RR activity and 200-mV improvement in overpotential for the 3D CoPB-C8 box structure compared to its 2D CoTPP counterpart. Synthetic tuning of peripheral alkyl substituents highlights the importance of supramolecular porosity and cavity size on electrochemical NO3RR activity. These findings establish the incorporation of 2D molecular units into 3D confined space microenvironments as an effective supramolecular design strategy for enhancing electrocatalysis. 相似文献
8.
Rong Zhang Hu Hong Xinghui Liu Shaoce Zhang Chuan Li Huilin Cui Yanbo Wang Jiahua Liu Yue Hou Pei Li Zhaodong Huang Ying Guo Chunyi Zhi 《Angewandte Chemie (International ed. in English)》2023,62(48):e202309930
Metal–organic framework-based materials are promising single-site catalysts for electrocatalytic nitrate (NO3−) reduction to value-added ammonia (NH3) on account of well-defined structures and functional tunability but still lack a molecular-level understanding for designing the high-efficient catalysts. Here, we proposed a molecular engineering strategy to enhance electrochemical NO3−-to-NH3 conversion by introducing the carbonyl groups into 1,2,4,5-tetraaminobenzene (BTA) based metal-organic polymer to precisely modulate the electronic state of metal centers. Due to the electron-withdrawing properties of the carbonyl group, metal centers can be converted to an electron-deficient state, fascinating the NO3− adsorption and promoting continuous hydrogenation reactions to produce NH3. Compared to CuBTA with a low NO3−-to-NH3 conversion efficiency of 85.1 %, quinone group functionalization endows the resulting copper tetraminobenzoquinone (CuTABQ) distinguished performance with a much higher NH3 FE of 97.7 %. This molecular engineering strategy is also universal, as verified by the improved NO3−-to-NH3 conversion performance on different metal centers, including Co and Ni. Furthermore, the assembled rechargeable Zn−NO3− battery based on CuTABQ cathode can deliver a high power density of 12.3 mW cm−2. This work provides advanced insights into the rational design of metal complex catalysts through the molecular-level regulation for NO3− electroreduction to value-added NH3. 相似文献
9.
Xiaoliang Lu Jinzhi Zhou Jinxiu Zhao Prof. Dan Wu Xuejing Liu Prof. Xiang Ren Prof. Qin Wei Prof. Huangxian Ju 《Chemphyschem》2023,24(20):e202300536
The electrocatalytic nitrate reduction reaction (NO3−RR) enables the reduction of nitrate to ammonium ions under ambient conditions. It was considered as an alternative reaction for the production of ammonia (NH3) in recent years. In this paper, we report that the Fe doping CoS2 nanoarrays can effectively catalyze the formation of NH3 from nitrate (NO3−) under ambient conditions. This is mainly due to the increase of the NO3− reaction active site by Fe doping and the porous nanostructure of the catalyst, which greatly improves the catalytic activity. Specifically, at −0.9 V vs. RHE, the NH3 yield rate (RNH3) of Fe−CoS2/CC is 17.8×10−2 mmol h−1 cm−2 with Faraday Efficiency (FE) of 88.93 %. Besides, such catalyst shows good durability and catalytic stability, which provides the possibility for the future application of electrocatalytic NH3 production. 相似文献
10.
Jing Geng Sihan Ji Dr. Meng Jin Dr. Chao Zhang Min Xu Prof. Guozhong Wang Prof. Changhao Liang Prof. Haimin Zhang 《Angewandte Chemie (International ed. in English)》2023,62(6):e202210958
The development of efficient electrocatalysts to generate key *NH2 and *CO intermediates is crucial for ambient urea electrosynthesis with nitrate (NO3−) and carbon dioxide (CO2). Here we report a liquid-phase laser irradiation method to fabricate symbiotic graphitic carbon encapsulated amorphous iron and iron oxide nanoparticles on carbon nanotubes (Fe(a)@C-Fe3O4/CNTs). Fe(a)@C-Fe3O4/CNTs exhibits superior electrocatalytic activity toward urea synthesis using NO3− and CO2, affording a urea yield of 1341.3±112.6 μg h−1 mgcat−1 and a faradic efficiency of 16.5±6.1 % at ambient conditions. Both experimental and theoretical results indicate that the formed Fe(a)@C and Fe3O4 on CNTs provide dual active sites for the adsorption and activation of NO3− and CO2, thus generating key *NH2 and *CO intermediates with lower energy barriers for urea formation. This work would be helpful for design and development of high-efficiency dual-site electrocatalysts for ambient urea synthesis. 相似文献
11.
Limin Wu Dr. Jiaqi Feng Libing Zhang Shunhan Jia Xinning Song Prof. Dr. Qinggong Zhu Prof. Dr. Xinchen Kang Dr. Xueqing Xing Prof. Dr. Xiaofu Sun Prof. Dr. Buxing Han 《Angewandte Chemie (International ed. in English)》2023,62(43):e202307952
The renewable-energy-powered electroreduction of nitrate (NO3−) to ammonia (NH3) has garnered significant interest as an eco-friendly and promising substitute for the Haber–Bosch process. However, the sluggish kinetics hinders its application at a large scale. Herein, we first calculated the N-containing species (*NO3 and *NO2) binding energy and the free energy of the hydrogen evolution reaction over Cu with different metal dopants, and it was shown that Zn was a promising candidate. Based on the theoretical study, we designed and synthesized Zn-doped Cu nanosheets, and the as-prepared catalysts demonstrated excellent performance in NO3−-to-NH3. The maximum Faradaic efficiency (FE) of NH3 could reach 98.4 % with an outstanding yield rate of 5.8 mol g−1 h−1, which is among the best results up to date. The catalyst also had excellent cycling stability. Meanwhile, it also presented a FE exceeding 90 % across a wide potential range and NO3− concentration range. Detailed experimental and theoretical studies revealed that the Zn doping could modulate intermediates adsorption strength, enhance NO2− conversion, change the *NO adsorption configuration to a bridge adsorption, and decrease the energy barrier, leading to the excellent catalytic performance for NO3−-to-NH3. 相似文献
12.
《中国化学快报》2023,34(6):107908
Nitrate (NO3−) is widely found in wastewater, which is harmful to human health and water environmental. Electrochemical reduction can convert NO3− to high value-added ammonia (NH3)/ammonium (NH4+) for pollutant removal and resource recovery. Currently, electrochemical nitrate reduction to produce ammonia (ENRA) is mostly focused on the preparation of high-performance catalysts, while ignoring the prerequisite for industrial application as the stable operation and optimal regulation of the process. Therefore, the review focused on wastewater treatment, based on the mechanism of electrochemical nitrate reduction for ammonia production and reactor construction (reactor, power supply system), then summarized the operation control strategies (such as reduction potential, nitrate concentration, inorganic ions, pH) that should be noted for ENRA. Finally, the challenges (system structure, economy) and prospects (ammonia recovery process, construction of large-scale ENRA system, application of real wastewater) of the field as it moves towards commercialization were discussed. It is hoped that this review will facilitate the scaling up of ENRA in the wastewater treatment field. 相似文献
13.
Zhiheng Gong Xuepeng Xiang Wenye Zhong Chenghao Jia Peiyan Chen Prof. Nian Zhang Prof. Shijun Zhao Prof. Weizhen Liu Prof. Yan Chen Prof. Zhang Lin 《Angewandte Chemie (International ed. in English)》2023,62(38):e202308775
The complexes of metal center and nitrogen ligands are the most representative systems for catalyzing hydrogenation reactions in small molecule conversion. Developing heterogeneous catalysts with similar active metal-nitrogen functional centers, nevertheless, still remains challenging. In this work, we demonstrate that the metal-nitrogen coupling in anti-perovskite Co4N can be effective modulated by Cu doping to form Co3CuN, leading to strongly promoted hydrogenation process during electrochemical reduction of nitrate (NO3−RR) to ammonia. The combination of advanced spectroscopic techniques and density functional theory calculations reveal that Cu dopants strengthen the Co−N bond and upshifted the metal d-band towards the Fermi level, promoting the adsorption of NO3− and *H and facilitating the transition from *NO2/*NO to *NO2H/*NOH. Consequently, the Co3CuN delivers noticeably better NO3−RR activity than the pristine Co4N, with optimal Faradaic efficiency of 97 % and ammonia yield of 455.3 mmol h−1 cm−2 at −0.3 V vs. RHE. This work provides an effective strategy for developing high-performance heterogeneous catalyst for electrochemical synthesis. 相似文献
14.
Prof. Lu-Hua Zhang Yangting Jia Jiayu Zhan Guomeng Liu Dr. Guanhua Liu Prof. Fei Li Prof. Fengshou Yu 《Angewandte Chemie (International ed. in English)》2023,62(22):e202303483
Electrochemically converting NO3− into NH3 offers a promising route for water treatment. Nevertheless, electroreduction of dilute NO3− is still suffering from low activity and/or selectivity. Herein, B as a modifier was introduced to tune electronic states of Cu and further regulate the performance of electrochemical NO3− reduction reaction (NO3RR) with dilute NO3− concentration (≤100 ppm NO3−−N). Notably, a linear relationship was established by plotting NH3 yield vs. the oxidation state of Cu, indicating that the increase of Cu+ content leads to an enhanced NO3−-to-NH3 conversion activity. Under a low NO3−−N concentration of 100 ppm, the optimal Cu(B) catalyst displays a 100 % NO3−-to-NH3 conversion at −0.55 to −0.6 V vs. RHE, and a record-high NH3 yield of 309 mmol h−1 gcat−1, which is more than 25 times compared with the pristine Cu nanoparticles (12 mmol h−1 gcat−1). This research provides an effective method for conversion of dilute NO3− to NH3, which has certain guiding significance for the efficient and green conversion of wastewater in the future. 相似文献
15.
Rate constants have been measured at 296 ± 2 K for the gas‐phase reactions of camphor with OH radicals, NO3 radicals, and O3. Using relative rate methods, the rate constants for the OH radical and NO3 radical reactions were (4.6 ± 1.2) × 10−12 cm3 molecule−1 s−1 and <3 × 10−16 cm3 molecule−1 s−1, respectively, where the indicated error in the OH radical reaction rate constant includes the estimated overall uncertainty in the rate constant for the reference compound. An upper limit to the rate constant for the O3 reaction of <7 × 10−20 cm3 molecule−1 s−1 was also determined. The dominant tropospheric loss process for camphor is calculated to be by reaction with the OH radical. Acetone was identified and quantified as a product of the OH radical reaction by gas chromatography, with a formation yield of 0.29 ± 0.04. In situ atmospheric pressure ionization tandem mass spectrometry (API‐MS) analyses indicated the formation of additional products of molecular weight 166 (dicarbonyl), 182 (hydroxydicarbonyl), 186, 187, 213 (carbonyl‐nitrate), 229 (hydroxycarbonyl‐nitrate), and 243. A reaction mechanism leading to the formation of acetone is presented, as are pathways for the formation of several of the additional products observed by API‐MS. © 2000 John Wiley and Sons, Inc. Int J Chem Kinet 33: 56–63, 2001 相似文献
16.
Giang Binh Truong Dr. Hung Tuan Duong Prof. Dr. Loi Duc Vu Dr. Thao Thi Huong Hoang 《欧洲无机化学杂志》2023,26(31):e202300371
The electrochemical reduction reaction of nitrogenous species such as NO3− (NO3RR) and N2 (NRR) is a promising strategy for producing ammonia under ambient conditions. However, low activity and poor selectivity of both NO3RR and NRR remain the biggest problem of all current electrocatalysts. In this work, we fabricated Cu-nanosphere film with a high surface area and dominant with a Cu(200) facet by simple electrodeposition method. The Cu-nanosphere film exhibits high electrocatalytic activity for NO3RR and NRR to ammonia under ambient conditions. In the nitrate environment, the Cu-nanosphere electrode reduced NO3− to yield NH3 at a rate of 5.2 mg/h cm2, with a Faradaic efficiency of 85 % at −1.3 V. In the N2-saturated environment, the Cu-nanosphere electrode reduced N2 to yield NH3 with the highest yield rate of 16.2 μg/h cm2 at −0.5 V, and the highest NH3 Faradaic efficiency of 41.6 % at −0.4 V. Furthermore, the Cu-nanosphere exhibits excellent stability with the NH3 yield rate, and the Faradaic efficiency remains stable after 10 consecutive cycles. Such high levels of NH3 yield, selectivity, and stability at low applied potential are among the best values currently reported in the literature. 相似文献
17.
Tieliang Li Shuhe Han Dr. Yuting Wang Jin Zhou Prof. Bin Zhang Prof. Yifu Yu 《Angewandte Chemie (International ed. in English)》2023,62(19):e202217411
As a potential substitute technique for conventional nitrate production, electrocatalytic nitrogen oxidation reaction (NOR) is gaining more and more attention. But, the pathway of this reaction is still unknown owing to the lack of understanding on key reaction intermediates. Herein, electrochemical in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and isotope-labeled online differential electrochemical mass spectrometry (DEMS) are employed to study the NOR mechanism over a Rh catalyst. Based on the detected asymmetric NO2− bending, NO3− vibration, N=O stretching, and N−N stretching as well as isotope-labeled mass signals of N2O and NO, it can be deduced that the NOR undergoes an associative mechanism (distal approach) and the strong N≡N bond in N2 prefers to break concurrently with the hydroxyl addition in distal N. 相似文献
18.
Runan Xiang Shihan Wang Peisen Liao Fangyan Xie Jiawei Kang Suisheng Li Jiahui Xian Linna Guo Prof. Guangqin Li 《Angewandte Chemie (International ed. in English)》2023,62(45):e202312239
Pyridine oximes produced from aldehyde or ketone with hydroxylamine (NH2OH) have been widely applied in pharmaceutics, enzymatic and sterilization. However, the important raw material NH2OH exhibits corrosive and unstable properties, leading to substantial energy consumption during storage and transportation. Herein, this work presents a novel method for directly synthesizing highly valuable pyridine oximes using in situ generated NH2OH from electrocatalytic NO reduction with well-design nanofiber membranes (Al-NFM) derived from NH2-MIL-53(Al). Particularly, 2-pyridinealdoxime, the precursor of antidote pralidoxime (2-PAM) for nerve agents suffering from scarcity and high cost, was achieved with a Faraday efficiency up to 49.8 % and a yield of 92.1 %, attributing to the high selectivity of NH2OH production on Al-NFM, further easily reacted with iodomethane to produce 2-PAM. This study proposes a creative approach, having wide universality for synthesizing pyridine and other oximes with a range of functional groups, which not only facilitates the conversion of exhaust gas (NO) and waste water (NO2−) into valuable chemicals especially NH2OH production and in situ utilization through electrochemistry, but also holds significant potential for synthesis of neuro detoxifying drugs to humanity security. 相似文献
19.
Danni Qin Shaojia Song Prof. Yanrong Liu Prof. Ke Wang Prof. Bing Yang Prof. Suojiang Zhang 《Angewandte Chemie (International ed. in English)》2023,62(28):e202304935
Electrochemical conversion of nitrate to ammonia is an appealing way for small-scale and decentralized ammonia synthesis and waste nitrate treatment. Currently, strategies to enhance the reaction performance through elaborate catalyst design have been well developed, but it is still of challenge to realize the promotion of reactivity and selectivity at the same time. Instead, a facile method of catalyst modification with ionic liquid to modulate the electrode surface microenvironment that mimic the role of the natural MoFe protein environment is found effective for the simultaneous improvement of NH3 yield rate and Faradaic efficiency (FE) at a low NaNO3 concentration of 500 ppm. Protic ionic liquid (PIL) N-butylimidazolium bis(trifluoromethylsulfonyl)imide ([Bim]NTf2) modified Co3O4−x is fabricated and affords the NH3 yield rate and FE of 30.23±4.97 mg h−1 mgcat.−1 and 84.74±3.43 % at −1.71 and −1.41 V vs. Ag/AgCl, respectively, outperforming the pristine Co3O4−x. Mechanistic and theoretical studies reveal that the PIL modification facilitates the adsorption and activation of NO3− as well as the NO3−-to-NH3 conversion and inhibits hydrogen evolution reaction competition via enhancing the Lewis acidity of the Co center, shuttling protons, and constructing a hydrogen bonded and hydrophobic electrode surface microenvironment. 相似文献
20.
《Journal of photochemistry and photobiology. A, Chemistry》2007,185(2-3):289-294
In this study, we investigated the effects of four inorganic anions (Cl−, SO42−, H2PO4−/HPO42−, and HCO3−/CO32−) on titanium dioxide (TiO2)-based photocatalytic oxidation of aqueous ammonia (NH4+/NH3) at pH ∼ 9 and ∼10 and nitrite (NO2−) over the pH range of 4–11. The initial rates of NH4+/NH3 and NO2− photocatalytic oxidation are dependent on both the pH and the anion species. Our results indicate that, except for CO32−, which decreased the homogeneous oxidation rate of NH4+/NH3 by UV-illuminated hydrogen peroxide, OH scavenging by anions and/or direct oxidation of NH4+/NH3 and NO2− by anion radicals did not affect rates of TiO2 photocatalytic oxidation. While HPO42− enhanced NH4+/NH3 photocatalytic oxidation at pH ∼ 9 and ∼10, H2PO4−/HPO42− inhibited NO2− oxidation at low to neutral pH values. The presence of Cl−, SO42−, and HCO3− had no effect on NH4+/NH3 and NO2− photocatalytic oxidation at pH ∼ 9 and ∼10, whereas CO32− slowed NH4+/NH3 but not NO2− photocatalytic oxidation at pH ∼ 11. Photocatalytic oxidation of NH4+/NH3 to NO2− is the rate-limiting step in the complete oxidation of NH4+/NH3 to NO3− in the presence of common wastewater anions. Therefore, in photocatalytic oxidation treatment, we should choose conditions such as alkaline pH that will maximize the NH4+/NH3 oxidation rate. 相似文献