Photocatalytic Activity For NO Removal Research Articles

Visible light photocatalytic NOx removal with suppressed poisonous NO2 byproduct generation over simply synthesized triangular silver nanoparticles coupled with tin dioxide.

The treatment or conversion of air pollutants with a low generation of secondary toxic substances has become a hot topic in indoor air pollution abatement. Herein, we used triangle-shaped Ag nanoparticles coupled with SnO2 for efficient photocatalytic NO removal. Ag triangular nanoparticles (TNPs) were synthesized by the photoreduction method and SnO2 was coupled by a simple chemical impregnation process. The photocatalytic NO removal activity results show that the modification with Ag TNPs significantly boosted the removal performance up to 3.4 times higher than pristine SnO2. The underlying roles of Ag TNPs in NO removal activity improvement are due to some advantages of Ag TNPs. Moreover, the Ag TNPs contributed photogenerated holes as the main active species toward enhancing the NO oxidation reaction. In particular, the selectivity toward green products significantly improved from 52.78% (SnO2) to 86.99% (Ag TNPs/SnO2). The formation of reactive radicals under light irradiation was also verified by DMPO spin-trapping experiments. This work provides a potential candidate for visible-light photocatalytic NO removal with low toxic byproduct generation.

A novel defect reassembly strategy for NH2-MIL-125(Ti) to enhance the photocatalytic NO removal activity

Photocatalysis technology has been widely used to eliminate typical air pollutants, but its further application is limited by the finite visible light response and severe charge carrier recombination. In this study, through a simple defect reassembly strategy, the carboxyl group of highly photosensitive eosin Y is successfully coordinated with the exposed Ti clusters in the defective NH2-MIL-125(Ti) to improve photocatalytic activity. The results demonstrate that the NO removal rate of the optimal sample (named D-NM-125/EY) is about 62.05%, which is 1.62 times that of the original NH2-MIL-125(Ti). The UV–Vis, PL, and photochemical characterization analysis confirm that the incorporation of eosin Y significantly can enhance the visible light absorption capacity and promote the photogenerated carriers separation, which may be due to that eosin Y can more easily absorb and utilize visible light to produce more photogenerated electron-hole pairs. Combining ESR with in-situ DRIFTS analysis, the possible photocatalytic mechanism is revealed, in which the reactive oxygen species generated in the photocatalytic process are the key factors for the successful degradation of NO into less toxic substances. This study will provide a new strategy for modifying MOFs photocatalysts to solve typical air pollution problems.

The defective NH2-MIL-125(Ti) was adjusted by a simple nitric acid etching method for switching on photocatalytic NO removal

In this paper, the photocatalytic properties of NH2-MIL-125(Ti) is enhanced by using a simple nitric acid etching method to form a ligand defect strategy. The structures and properties of the samples are characterized by XRD, SEM, XPS, BET, TG, and UV–vis etc. The results display that the yield of modified NH2-MIL-125(Ti) photocatalytic NO removal experiment is significantly improved based on excellent photoresponse capacity. The optimal sample (0.1 mol/L HNO3-NH2-MIL-125(Ti)) shows excellent photocatalytic activity for NO removal under visible light irradiation (42.69%), which was 1.84 times higher than that of the original NH2-MIL-125(Ti).

Synergetic effect of CQD and oxygen vacancy to TiO2 photocatalyst for boosting visible photocatalytic NO removal

The wide band gap of TiO2 photocatalyst material limits its application in the field of visible photocatalysis. In this paper, oxygen vacancies and carbon quantum dots (CQD) with up-conversion character were proposed to improve the photocatalytic activity for NO removal of TiO2 under visible light irradiation. The one-dimensional TiO2 nanotube (TNs), TNs containing oxygen vacancies (OVTNs), TNs of composite CQD (CQD-TNs) and OVTNs of composite CQD (CQD-OVTNs) were prepared, respectively. Furthermore, the influence of oxygen vacancies and CQD on the removal of NOx by photocatalysis were explored. It is found that CQD-OVTNs exhibits the conspicuous synergetic effect of CQD and oxygen vacancy to boost visible photocatalytic NO removal, the NO removal efficiency was about 12, 2, and 2.6 times to TNs, OVTNs and CQD-TNs. Also, CQD-OVTNs exhibits the NO2-inhibited property during the process of photocatalytic NO removal. Finally, the synergetic mechanism of CQD and oxygen vacancies to TNs for boosting visible photocatalytic NO removal was revealed.

Au Nanoparticles Loaded Bi5Ti3FeO15 Ferroelectric Nanosheets with Enhanced Photocatalytic Activity for NO Removal

Au Nanoparticles Loaded Bi5Ti3FeO15 Ferroelectric Nanosheets with Enhanced Photocatalytic Activity for NO Removal

Efficient photothermal-assisted photocatalytic NO removal on molecular cobalt phthalocyanine/Bi2WO6 Z-scheme heterojunctions by promoting charge transfer and oxygen activation

Developing a high-performance photocatalyst with an efficient charge transfer pathway and reasonable active sites for photocatalytic NO removal is a formidable challenge. Herein, a novel Z-scheme molecular cobalt phthalocyanine(CoPc)/Bi2WO6 photothermal-assisted photocatalyst was elaborately designed. The interfacial Co-O-W bond and built-in electric field(BIEF) between Bi2WO6 and CoPc promote a cascade Z-scheme charge transfer system from Bi2WO6 to CoPc, thereby facilitating the charge separation and retaining high redox potential. Meanwhile, the Co-N4(II) sites of CoPc can capture more photoexcited electrons migrating from Z-scheme of the CoPc/Bi2WO6 composite, which facilitates the electron transfer to O2 for the generation of •O2-. Moreover, the photothermal effect of CoPc can further improve the O2 activation efficiency. Consequently, the obtained photocatalysts exhibit superior photocatalytic activity for NO removal (74.9%) and lower generation of toxic NO2 (<6 ppb) by-products compared with pristine Bi2WO6. This work offers a new idea for constructing high-efficiency NO photo-oxidation systems.

The excellent photocatalytic NO removal performance relates to the synergistic effect between the prepositive NaOH solution and the g-C3N4 photocatalysis

Photocatalysis technology is used to remove the low concentration NO in recent years. However, the effect of this process is not very satisfactory. In this study, it was found that the prepositive NaOH solution could significantly improve the photocatalytic NO removal activity of g-C3N4. The apparent quantum yield of g-C3N4 in the NO removal process was increased 3.5 times by the prepositive NaOH solution. The reason is that there was a synergistic effect formed between the prepositive NaOH solution and the photocatalytic NO removal process. The prepositive NaOH solution not only could increase the humidity and pH value in the photocatalytic unit, but also could improve the adsorption ability of g-C3N4 for the H2O, NO, and O2. Moreover, the prepositive NaOH solution reduced the difficulty of the photogenerated carriers’ transport and the ·OH generation. This study provided a new idea for the removal of low-concentration NOx.

The photocatalytic NO-removal activity of g-C3N4 significantly enhanced by the synergistic effect of Pd0 nanoparticles and N vacancies

Pd0 and N vacancy co-modified g-C3N4 displayed excellent NO-removal activity.

Fabrication of 1D/2D BiPO4/g-C3N4 heterostructured photocatalyst with enhanced photocatalytic efficiency for NO removal

The visible light photocatalytic removal of NO in air is a promising way. BiPO4 is restricted by its wide band gap and can only be responded to ultraviolet light. Herein, 1D BiPO4 nanorod/2D g-C3N4 heterostructured photocatalyst was successfully synthesized via a facile one-step hydrothermal process for efficient visible light photocatalytic removal of NO. With simulated sunlight irradiation, the photocatalytic NO removal activity of the BiPO4/g-C3N4 (64%) is much higher than that of the pure BiPO4 (7.2%) and g-C3N4 (50%). Its excellent photocatalytic performance was ascribed to broadening the light response range to visible light and boosting the separation and transfer of photogenerated electrons and holes. The NO photocatalytic removal mechanism was proposed by the free radical trapping experiment and in situ DRIFTS research. The present study might induce a new means to design BiPO4-based heterostructured photocatalysts for the removal of NO from air pollution under simulated solar light irradiation.

Highly efficient photocatalytic NO removal and in situ DRIFTS investigation on SrSn(OH)6

A novel SrSn(OH)6 photocatalyst with large plate and particle size were synthesized via a facile chemical precipitation method. The photocatalytic activity of the SrSn(OH)6 was evaluated by the removal of NO at ppb level under UV light irradiation. Based on the ESR measurements, SrSn(OH)6 photocatalyst was found to have the ability to generate the main active species of O2•−, •OH and 1O2 during the photocatalytic process. Moreover, SrSn(OH)6 photocatalyst not only exhibits high photocatalytic activity for NO removal (79.6%), but also has good stability after five cycles. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to investigate the NOx transfer pathway and the intermediate products distribution during the adsorption and photocatalytic NO oxidation process. The present work not only provides an efficient material for air pollutants purification at room temperature but also in-depth understanding of the mechanism involved in the photocatalytic NO removal process.

Photocatalytic air purification: Effect of HNO3 accumulation on NOx and VOC removal

The effect of photocatalytically generated surface HNO3 on NOx and VOC removal activity is investigated using three very different photocatalytic films, namely, P25 TiO2, a commercial exterior paint (produced by STO Gmb) and a commercial air-purifying curtain fabric (IKEA). The paint required accelerated weathering and the cloth UV-preconditioning before exhibiting significant activity. When tested using the removal of nitric oxide ISO 22197-1:2016, the NO ISO, all films exhibited decreasing NOx removal activity and decreasing photocatalytic activity for NO removal with increasing irradiation time, so much so that both the STO paint and P25 films showed little NOx removal activity after the 5 h irradiation period. In all cases the loss in activity was attributed to the generation of a surface layer of HNO3, which was found to persist for at least 15 h and up to 7 days on a P25 film but could be readily rinsed away. The CaCO3 in the STO film, and the fibrous nature of the IKEA cloth appeared to largely eliminate the negative effect on NOx removal activity after 7 days. The activities exhibited by these films for the photocatalysed oxidation of acetaldehyde appeared unaffected by the presence of a photocatalytically generated HNO3 film. The relevance of the results to current, commercial photocatalytic products for air purification is discussed briefly.

Tuning the Active Sites of Atomically Thin Defective Bi12O17Cl2 via Incorporation of Subnanometer Clusters.

The introduction of subnanometer clusters as active sites on the surface of photocatalysts for efficiently tuning the selectivity and activity of the photocatalyts is still a challenge. Herein, the subnanometer Ag/AgCl clusters were incorporated on atomically thin defective Bi12O17Cl2 nanosheets via rebinding with unsaturated Cl atoms. Benefiting from the surficial Bi vacancies (VBi) and Bi-O vacancies (VBi-O) in this atomically thin architecture, the local atomic arrangement was tuned so that the subnanometer Ag/AgCl clusters were successfully incorporated. An enhancement of photocatalytic activity for NO removal was achieved in which the activity is 3 times higher than that of Bi12O17Cl2 and 1.8 times higher than that of defective Bi12O17Cl2. The substitution of the active sites from surficial VBi and VBi-O to be subnanometer Ag/AgCl clusters enables a tunable redox potential and different reaction mechanisms in NO removal. Moreover, the selectivity of the photoinduced redox reaction on NO oxidation and CO2 reduction was achieved via introducing an extra energy level.

Synergistic photocatalytic NO removal of oxygen vacancies and metallic bismuth on Bi12TiO20 nanofibers under visible light irradiation

Tailoring the semiconductors with non-precious metals or defects have been demonstrated to be a fascinating and prospective approach for environmental remediation. In this work, Bi metal and oxygen vacancies (OVs) co-modified Bi12TiO20 nanofibers (Bi/BTO) photocatalysts were synthesized through electrospinning technique and subsequent chemical reduction method for the first time. The Bi/BTO composite photocatalysts exhibit significantly higher photocatalytic NO removal activity than that of pristine BTO under visible light irradiation. The improvement of photocatalytic performance is ascribed to the integrative effect of OVs and surface plasmon resonance (SPR) effect of Bi particles. The presence of OVs is confirmed by X-ray photoelectron spectroscopy and electron paramagnetic resonance spectroscopy. The density functional theory (DFT) calculations reveal that the OVs in BTO induce the formation of a defect level, which is beneficial to increase light absorption. In addition, Bi can act as an electron sink, boosting the separation of photoinduced electron-hole pairs. The trapping experiment and electron spin resonance spectra indicate that the main active species are ·O2− and h+. Moreover, the reaction process over 3% Bi/BTO is monitored by in situ infrared spectroscopy (in situ FTIR) and a reasonable photocatalytic mechanism of NO removal on Bi/BTO is proposed through a combination of experimental and theoretical results.

Flower-like Bi0/CeO2−δ plasmonic photocatalysts with enhanced visible-light-induced photocatalytic activity for NO removal

Plasmonic bismuth (Bi0) nanoparticle-decorated flower-like CeO2−δ (Bi0/CeO2−δ) photocatalysts with abundant oxygen vacancies (OVs) were synthesized via a solvothermal method. The OVs can not only improve the separation of electron-hole pairs, but also facilitate the adsorption and activation of gas molecules (NO/O2). In addition, the Bi0 nanoparticles can enhance the visible light response and prevent the recombination of charge carriers by virtue of the surface plasmon resonance (SPR) effect, achieving an excellent ability for NO elimination and NO2 inhibition under visible light irradiation. Density functional theory (DFT) calculations confirm that the Schottky barrier between Bi0 and CeO2−δ accompanied with the OVs are pivotal for the migration of photogenerated charge carriers to involve in the photocatalytic NO removal. Trapping experiments and in situ FTIR spectroscopy were conducted to explore the mechanism of the photocatalytic NO removal, suggesting that the photocatalytic NO removal can be significantly enhanced by introducing abundant OVs and the involvement of Bi0 metal nanoparticles.

Double build-in electric fields mediated double Z-scheme semiconductor-nonmetal plasma heterojunction for dark-full-spectrum-driven environmental clean

The core-shell double Z-scheme Zn2SnO4/BiO2-x/Bi2O2.75 heterojunction was prepared by in-situ hydrothermal reaction. The electrons of BiO3− were captured by interfacial Zn/Sn atoms of positively charged Zn2SnO4 and crystallized in-situ to form core-shell Zn2SnO4/BiO2-x. Then, Bi2O2.75 crystal nucleus generated by homogeneous nucleation nucleated and grown heterogeneously again on the surface of Zn2SnO4/BiO2-x to form core-shell Zn2SnO4/BiO2-x/Bi2O2.75 heterojunction with the increased concentration of oxygen vacancies, meanwhile forming electrostatic attraction and potential difference-induced build-in electric fields at the interfaces of Zn2SnO4/BiO2-x and BiO2-x/Bi2O2.75. The transformation from Ⅱ-Ⅰ-type to Ⅱ-Ⅱ-type, double Z-double heterojunction was achieved due to polarization charge transfer and the synergistic effect of double build-in electric fields and oxygen vacancies. The higher concentration of O2– and OH radicals were generated by Zn2SnO4/BiO2-x/Bi2O2.75 in dark and under visible-NIR light irradiation due to the enhanced O2 activation, improved carriers’ separation and stronger redox ability. Therefore, semiconductor-nonmetal plasma coupling heterojunction exhibited the enhanced dark-full-spectrum-driven photocatalytic activity for NO removal and organic pollutants degradation.

Carbon vacancies and hydroxyls in graphitic carbon nitride: Promoted photocatalytic NO removal activity and mechanism

The carbon vacancies and hydroxyls co-modified CN (CHCN) was successfully prepared using a green hydrothermal method. During the hydrothermal process, the water played an important role in etching the unstable partial of bulk CN to introduce carbon vacancies and hydroxyls into the CHCN nanosheets. The carbon vacancies and hydroxyls co-modified CHCN displayed 2.2 times higher photocatalytic NO removal performance than that of pristine CN. Detailed experimental characterizations and density functional theory calculations revealed that the enhanced photocatalytic NO removal performance of CHCN nanosheet was largely ascribed to synergistic effects of carbon vacancies and hydroxyls. The carbon vacancies could narrow the bandgap of modified CHCN nanosheet to improve the light-absorbing capability; the hydroxyls enabled to form stable covalent bonds acted as electron transport channels to facilitate the charge carrier separation. This study may provide new insights into vacancies engineering for enhancing the photocatalytic activity of CN-based photocatalysts.

Mo-doped carbon nitride homojunction to promote oxygen activation for enhanced photocatalytic performance

Oxygen as an economic and ubiquitous oxidant plays a significant role in catalysis environmental remediation. However, the high thermodynamic stability of O2 limits the practical application. Herein, we reported a novel Mo doped carbon nitride (Mo-CN/g-CN) homojunction via the in-situ growth strategy. The strong interaction between Mo-CN and g-C3N4 enhanced visible-light response and photogenerated electrons and holes pairs separation, which were beneficial for photocatalytic activity. Importantly, theoretical calculation and experiments confirmed that Mo atoms on the surface of Mo-CN/g-CN could provide abundant electrons to the adsorbed O2 to promote the generation of O2−, thus enhancing the photocatalytic performance. Consequently, the obtained Mo-CN/g-CN reveals excellent photocatalytic NO removal activity, demonstrating its promise for air purification. This current work gives a novel insight for O2 activation in the application of photocatalytic environmental remediation.

Photocatalytic removal of NO by intercalated carbon nitride: The effect of group IIA element ions

In this study, Group IIA element ion-doped g-C3N4 samples were synthesized to eliminate above two disadvantages and increase photocatalytic NO removal activity. The experimental results showed that the Group IIA element ions could form coordination bonds with the nitrogen atoms in the triazine rings of g-C3N4 that distorted the g-C3N4 structure because of uneven force. The structure distortion destroyed the surface electronic delocalization and suppressed the recombination of surface charge carriers. Additionally, the formed coordinate bonds connected two adjacent layers and served as interlayer electron channels, which could significantly improve the electron transport between two layers. Additionally, structural distortions created more amino and imino groups, which are the chemisorption sites of O2. Therefore, the modified g-C3N4 samples produced more reactive oxygen species to remove NO. The degree of distortion and the NO removal activity increased as the Group IIA atomic number increased.

In situ construction of biocompatible Z-scheme α-Bi2O3/CuBi2O4 heterojunction for NO removal under visible light

The design of efficient, stable and biocompatible photocatalysts for air purification is still a challenge. In this work, we report a Z-scheme α-Bi2O3/CuBi2O4 composite with high-quality interfaces using an in situ synthesis method. The α-Bi2O3/CuBi2O4 displays significantly enhanced photocatalytic activity for NO removal (30 %) in comparison with α-Bi2O3 (17 %) under visible light irradiation. Based on characterizations, theoretical calculations and ESR tests, the Z-scheme migration mechanism of photoinduced electrons and holes on α-Bi2O3/CuBi2O4 heterojunction was proposed. The formation of intermediates and products was monitored by in situ DRIFTS. The NO adsorption and activation on α-Bi2O3/CuBi2O4 surface are more favorable than that on α-Bi2O3 surface. The α-Bi2O3/CuBi2O4 also shows high selectivity for the conversion of NO to NO- 3. Moreover, the cytotoxicity of α-Bi2O3/CuBi2O4 exposed to human alveolar epithelial cell has been evaluated for its potential application in air purification. This work provides a new perspective regarding the design of Z-scheme heterojunctions by an in situ method and a promising photocatalyst suitable for air pollution control.

TiO2 with exposed (001) facets/Bi4O5Br2 nanosheets heterojunction with enhanced photocatalytic for NO removal

A TiO2 with exposed (001) facets/Bi4O5Br2 nanosheets heterojunction (TNS/BOB) was fabricated via a hydrothermal and electrostatic self-assembly method. The photocatalytic activity for NO removal was evaluated under simulated solar light irradiation. Through optimizing the content of TNS nanosheets, the photo-oxidative NO removal rate of 15% TNS/BOB was increased by up to 54.3%. This value is much higher than that of the individual components TNS (31.1%) and BOB (37.7%). Through capturing experiments and electron spin resonance (ESR) measurements, the main active species in the photocatalytic process were identified as · and ·OH. Discrete Fourier transform computation results and ESR tests revealed that the photo-induced electrons in TNS should recombine with the holes in BOB, leading to effectively promoted charge separation at the TNS/BOB interface through the Z-type charge transfer. This work showed that with appropriate facet control and heterojunction design TiO2 can be used as an effective visible-light photocatalyst material.