Formation Of Internal Electric Field Research Articles

Photocatalytic fuel cell assisted by Fenton-like reaction for p-Chloronitrobenzen degradation and electricity production through S-scheme heterojunction C3N5 modified TNAs photoanode: Performance, DFT calculation and mechanism

Photocatalytic fuel cell (PFC) is a promising technology to recover usable energy from wastewater through the degradation of pollutants, whereas the complex preparation procedures and high photogenerated carrier recombination efficiency of photoanode remains an urgent challenge to improve the PFC performance. Herein, PFC with S-scheme heterojunction C3N5/TNAs photoanode assisted by Fenton-like reaction (C3N5/TNAs-PFC-Fenton) system was built for p-Chloronitrobenzene degradation and electricity production. The working function confirmed the band bending of C3N5 and TNAs, and density functional theory calculations indicated the formation of internal electric field at heterojunction interface of C3N5 and TNAs, which promoted visible-light absorption capacity and charge transfer property of C3N5/TNAs photoanode. The incorporation of Fenton-like reaction into C3N5/TNAs-PFC-Fenton system could effectively enhance p-Chloronitrobenzene degradation and electricity production by participating in free radical chain reaction and stimulating electron transfer. The radical trapping experiments confirmed that •OH and photogenerated electron were main reactive species, and photogenerated hole, •O2− and 1O2 were also participated in p-Chloronitrobenzene degradation. The p-Chloronitrobenzene degradation pathway was interpreted and the overall toxicity of p-Chloronitrobenzene was relieved after treatment in C3N5/TNAs-PFC-Fenton system. The C3N5/TNAs-PFC-Fenton system exhibited fine universality for degradation of organic pollutants and electricity production.

Build-in electric field in CuWO4/covalent organic frameworks S-scheme photocatalysts steer boosting charge transfer for photocatalytic CO2 reduction

Covalent organic frameworks (COFs) are crystalline porous materials with enormous potential for realizing solar-driven CO2-to-fuel conversion, yet the sluggish transfer/separation of photoinduced electrons and holes remains a compelling challenge. Herein, a step (S)-scheme heterojunction photocatalyst (CuWO4-COF) was rationally fabricated by a thermal annealing method for boosting CO2 conversion to CO. The optimal CuWO4/COF composite sample, integrating 10 wt% CuWO4 with an olefin (C═C) linked COF (TTCOF), achieved a remarkable gas–solid phase CO yield as high as 7.17 ± 0.35 μmol g−1h−1 under visible light irradiation, which was significantly higher than the pure COF (1.6 ± 0.29 μmol g−1h−1). The enhanced CO2 conversion rate could be attributable to the interface engineering effect and the formation of internal electric field (IEF) directing from TTCOF to CuWO4 according to the theoretical calculation and experimental results, which also proves the electrons transfer from TTCOF to CuWO4 upon hybridization. In addition, driven by the IEF, the photoinduced electrons can be steered from CuWO4 to TTCOF under visible light irradiation as well-elucidated by in-situ irradiated X-ray photoelectron spectroscopy, verifying the S-scheme charge transfer pathway over CuWO4/COF composite heterojunctions, which greatly foster the photoreduction activity of CO2. The preparation technique of the S-scheme heterojunction photocatalyst in this study provides a paradigmatic protocol for photocatalytic solar fuel generation.

A novel bimetallic MXene derivative QD-based ECL sensor for miRNA-27a-3p detection

In this work, a novel ECL biosensor has been developed based on bimetallic MXene derivative QDs (Mo2TiC2 QDs) and SnS2 nanosheets/lipid bilayer to detect the gastric cancer marker miRNA-27a-3p. On the one hand, the inter-band excitation of Mo2TiC2 QDs can inject the additional carriers, which were less suppressed by boundary effects and made a significant contribution to the luminescence process. Semiconductor Mo2TiC2 further inhibited the formation of internal electric field and potential oxidation. Therefore, Mo2TiC2 QDs processed superior luminous intensity and better stability. On the other hand, SnS2 nanosheets coated with phospholipid bilayer were designed as sensing interface. SnS2 nanosheets not only enhanced the luminous intensity of Mo2TiC2 QDs by virtue of their large surface area and low dielectric constant, but also improved the stability of lipid bilayer. Due to the excellent properties and synergy work of Mo2TiC2 QDs and the lipid bilayer-modified SnS2 nanosheets, the sensing system displayed high sensitivity and good reproducibility in the analysis application. As a result, the biosensor displayed good linear correlation between the ECL intensity and the concentration of miRNA-27a-3p over a wide range from 1 fM to 10 nM with the detection limit as low as 1 fM. The sensing system including the joint contribution of Mo2TiC2 QDs, SnS2 nanosheets and lipid bilayers had great potential for clinical applications.

A S‐Scheme MOF‐on‐MOF Heterostructure

AbstractConstructing MOF‐on‐MOF heterojunction with elaborate charge transfer mechanism and interface is a promising strategy for improving the photocatalytic properties of MOFs. Herein, a Step‐scheme (S‐scheme) MIL‐125‐NH2@CoFe Prussian blue analogue (PBA) heterojunction is reported for the first time. The MOF‐on‐MOF heterostructure exhibits a sandwich‐like morphology with hollow CoFe PBA nanocages selectively assembled on the top‐down surfaces of MIL‐125‐NH2 nanocakes. Experimental findings and theoretical simulation results reveal the formation of internal electric field via interfacial TiOCo bonds at the heterojunction, providing driving force and atomic transportation highway for accelerating the S‐scheme charge transfer and enhancing the redox performance. Contributed further by the hollow sandwich‐like structures with increased active site exposure, the designed MOF‐on‐MOF heterojunction exhibits significantly enhanced photocatalytic activity for degradation of various organic pollutants. This study provides insights toward the rational design of semiconducting MOF‐based heterojunctions with improved properties.

Synergetic effect of oxygen vacancies coupled with in-situ Bi clusters in Bi2WO6 for enhancing photocatalytic CO2 reduction

In order to improve photocatalytic performance, Bi2WO6 (BWO) with oxygen vacancies (Vo) and in-situ loaded Bi clusters was prepared by using mild aluminothermic reduction. From morphological and structural characterization, it can be seen that Bi clusters gradually precipitates from the surface of BWO owing to oxygen vacancies as annealing temperature increases. The photocatalyst annealed at 450 ℃ (Bi-Vo-BWO-450) demonstrates the best photocatalytic CO2 reduction performance with CO and CH4 production rate reaching 5.94 and 1.18 µmol·g−1·h−1, respectively. From experimental analyses and first principles calculation, in-situ Bi clusters exhibit the unique surface plasma resonance (SPR) effect and induce the formation of internal electric field by Schottky barrier between Bi and BWO, which enhance the light absorption of photocatalyst and improve charge separation and transfer efficiency. Meanwhile, Bi clusters act as the surface active sites to activate CO2 adsorption for reducing the rate-limiting potential barrier in photocatalytic CO2 reduction, and improve the activity of oxygen vacancies by preventing the oxygen-containing groups from being adsorbed at the oxygen defect site. This work has a clear understanding of the synergetic effect between Bi clusters and oxygen vacancies, and provides a new enlightenment into high-efficiency catalyst.

Tunable Bi-bridge S-scheme Bi2S3/BiOBr heterojunction with oxygen vacancy and SPR effect for efficient photocatalytic reduction of Cr(VI) and industrial electroplating wastewater treatment

Surface plasmon resonance (SPR), oxygen vacancy modification and the construction of S-scheme heterostructure are important strategies to enhance visible-light absorption and improve photocatalytic performance. Here, a Bi-bridge S-scheme Bi2S3/BiOBr heterojunction (Bi2S3/Bi/BiOBr) with oxygen vacancies and SPR effect of Bi metal was prepared by one-pot solvothermal method for Cr(VI) reduction. The 3:10 Bi2S3/Bi/BiOBr exhibited superior visible-light photocatalytic reduction performance with 95.82 % Cr(VI) removal efficiency. Additionally, the 3:10 Bi2S3/Bi/BiOBr showed high stability and good anti-interference ability, and can effectively remove Cr(VI) from industrial electroplating wastewater with 97 % of Cr(VI) removal efficiency and residual Cr(VI) concentration of 0.304 mg/L, meeting the industrial effluent standard, which made it potentially attractive for real wastewater treatment. The enhanced photocatalytic performance of Bi2S3/Bi/BiOBr heterojunction was attributed to Bi metal SPR effect and the role of Bi as e-bridge, the presence of oxygen vacancies, the formation of internal electric field and S-scheme charge transfer, which were confirmed by various experimental results and density functional theory (DFT) calculations. This work provided theoretical and experimental reference for the construction of stable S-scheme heterojunctions with high catalytic activity and anti-interference, and a reliable solution for Cr(VI) removal from electroplating wastewater.

Fire-resistant iron-based phosphates/phosphorus-doped carbon composites derived from phytic acid-treated metal organic frameworks as high-efficiency microwave absorbers

Considering the electromagnetic pollution in harsh environments, it is vital to prepare multifunctional microwave absorbers to broaden their application fields. Herein, fire-resistant iron-based phosphates/phosphorus-doped carbon composites were annealed from phytic acid-treated metal organic frameworks. Through tailoring the dosage of phytic acid used in the preparation process, composites with diverse morphologies, crystal structures, electric and microwave absorption properties are obtained. When the dosage of phytic acid used reaches 4 mL, the obtained composite, Fe2P4O12/phosphorus-doped carbon, possesses the best microwave absorption performance with a minimum reflection loss of −67.6 dB (2.0 mm) and an effective absorption bandwidth of 5.76 GHz (2.1 mm, 12.24–18 GHz). The microwave attenuation could be mainly attributed to the high conductivity brought by phosphorus-doped carbon, and polarization relaxations triggered by dipoles, functional groups, and unbalanced charges at interfaces. Specifically, the charge density distribution, obtained with density functional theory (DFT), suggests the occurrence of intense charge transfer and formation of internal electric field at P-carbon, O-carbon, and iron-based phosphates/phosphorus-doped carbon interfaces. Meanwhile, the as-prepared iron-based phosphates/phosphorus-doped carbon composites possess good fire-resistant property. The work provides a novel idea to construct multifunctional materials with high-efficient microwave absorption to broaden their application fields.

Construction of highly active WO3/TpPa-1-COF S-scheme heterojunction toward photocatalytic H2 generation

• WO 3 /TpPa-1-COF is synthesized through an in-situ growth approach. • Internal electric field drives the charge carrier diffusion in S-scheme mode. • WO 3 /TpPa-1-COF has strong redox abilities and high charge separation efficiency. • WO 3 /TpPa-1-COF display superior photocatalytic H 2 generation performance. The rapid charge recombination and low surface reaction kinetics are the two major constraints to the photocatalytic performance of covalent organic frameworks (COFs). To accelerate the charge separation behavior, TpPa-1-COF is decorated with WO 3 via an in-situ growth approach, and the resultant WO 3 /TpPa-1-COF composites show significantly improved photocatalytic performance. Especially, when the WO 3 loading arrives at 3 wt%, 3%WO 3 /TpPa-1-COF exhibits the maximum photocatalytic H 2 evolution rate of 19.89 mmol g −1 h −1 , which is approximately 4.8 times higher than that of pure TpPa-1-COF. The apparent quantum efficiency (AQE) of 3%WO 3 /TpPa-1-COF at 420 nm is detected to be 12.4%. X-ray photoelectron spectroscopy (XPS) characterization confirms the formation of internal electric field between WO 3 and TpPa-1-CF, which can drive the photogenerated charge carrier diffusion in S-scheme mode. As a result, WO 3 /TpPa-1-COF composite possesses high charge separation efficiency and strong redox ability, which is further supported by the photoelectrochemical results, thus benefiting the photocatalysis process. This work provides a rational strategy to modify COFs in photocatalytic water splitting.

Fabricating S-scheme BiOBr/Zn2In2S5 heterojunction for synergistic adsorption-photocatalytic degradation of tetracycline

Harnessing affordable photocatalysts with high performance for boosting charge separation is an effective strategy to reinforce wastewater contaminant control. Herein, we reported a self-assembled S-scheme heterostructure BiOBr/Zn2In2S5 (BZS) nanoflower with the formation of internal electric field to promote the synergistic effect of adsorption and photocatalysis. The result showed that 7 wt% BiOBr/Zn2In2S5 (BZS-7) has highest tetracycline (TC) adsorption capacity of 34.85 mg g−1, which was fitted well the pseudo-second-order and Langmuir isotherm models. Then the synergistic degradation rate could reach 97.52% after 40 min visible light irradiation, which was 1.34 times higher than that of Zn2In2S5. BZS-7 also performed excellent adsorption-photocatalytic synergy on the removal of TC in simulated seawater and continuous flow reactor, with removal efficiency about 81.11% and 34.35%, respectively. The improved performance could be attributed to unique structures and high exposure surface of reassembled morphologies after the introduction of BiOBr. The antibacterial activity and ecotoxicity evaluation of TC intermediate byproducts indicated that the proposed degradation pathways presented reduced acute and chronic toxicity. The synergistic process of cost-effective S-scheme heterojunction photocatalysts holds the research for practical on-site wastewater remediation.

Band bending caused by forming heterojunctions in Cu-Cu2O/rGO-NH2 semiconductor materials and surface coordination of N-methylimidazole, and the intrinsic nature of synergistic effect on the catalysis of selective aerobic oxidation of alcohols

In this work, three materials of Cu-Cu2O/rGO-NH2-4.4/1, -1/1 and -1/10.4, in which the numeric suffices denote the ratio of Cu/Cu2O in the materials, were described and characterized using various analytical techniques including FTIR, XRD, SEM, HRTEM, XPS and Raman spectroscopy. To probe the band structures of these materials, UPS, cyclic voltammetry, and UV–vis reflection spectroscopy were also employed. The formation of heterojunctions in the ternary materials tune their band structures by raising the energy level of valence band maximums (VBMs), inducing an internal electric field (IEF) and an electron accumulation layer (EAL) within the materials. Augment of copper content in the materials can enhance the energy level rising. The coordination of N-methylimidazole (NMI) with Cu2O of the materials can also contribute to raising the energy level. The changes in these electronic properties bring about a synergistic effect in selective aerobic oxidation of benzylic alcohols via improving O2 activation and facilitation of electron transfer between the catalyst and the reactants due to the rising of the energy level of VBM and the formation of IEF.

Construction of internal electric field in imprinted poly (ionic liquid)-TiO2 composite nanoreactor for improving hole directional enrichment and selective photodegradation

In this work, imprinted poly (ionic liquid)-TiO2 composite nanoreactor (I-PIL-TiO2) was synthesized by the microwave-assisted in-situ polymerization in non-toxic aqueous phase. The S-scheme heterojunction made of I-PIL wrapping TiO2 had a tight and large interface region. According to Mott–Schottky's experiment and theoretical calculation, the obtained composite nanoreactor had improved the rapid separation and migration of carriers and increased carrier density, which was closely related to the formation of internal electric field (IEF) driven channels in the interface. The results showed that the orientation of the IEF was from TiO2 to I-PIL, so that photogenerated holes (h+) were accelerated to migrate to I-PIL through the interface channel, which was conducive to h+ directly attacking LEV. The photocatalytic activity of I-PIL-TiO2 was 1.69 times higher than that of TiO2. More interestingly, the presence of IEF increased the enrichment ability of h+ in imprinted cavities, improved the selective degradation ability of the composite nanoreactor, and maintained stable performance in the swine wastewater. After five degradation reactions, the composite still maintained good stability. This work provided a feasible way to synthesize polymer-inorganic composite photocatalytic materials with good interfacial charge transfer by simple and green method.

Step-scheme heterojunction g-C3N4/TiO2 for efficient photocatalytic degradation of tetracycline hydrochloride under UV light

Construction of heterojunction between semiconductors is considered an effective strategy for enhancing photocatalytic capability. Herein, this work prepared an abundant porous g-C3N4/TiO2 photocatalyst, with the two-dimensional (2D) nanosheet g-C3N4 and nanoparticle TiO2. The heterojunction both enhanced the ultraviolet (UV) light absorption ability, and inhibited the recombination of photogenerated electron-hole (h+) pairs. As expected, the optimal 4 % g-C3N4/TiO2 (g-C3N4:TiO2 = 1:25) exhibited a prominent degradation efficiency of 96.53 % in the photocatalytic performance of tetracycline hydrochloride (TCH) under UV irradiation. The recycling of the heterojunction photocatalyst g-C3N4/TiO2 remained stability and reusability. The main active species were·O2-, h+ and·OH, and the formation of internal electric field on the step-scheme (S-scheme) heterojunction interface accelerated the migration of photogenerated carriers. Moreover, several environmental factors on degradation such as dose, pH, and the initial concentration of TCH were investigated. This work could be spread to the conceive of other S-scheme heterojunction photocatalysts in application to different environmental demands.

Ag nanoparticles decorated Z-scheme CoAl-LDH/TiO2 heterojunction photocatalyst for expeditious levofloxacin degradation and Cr(VI) reduction

Conventional type-II heterojunctions are unable to degrade pollutants efficiently owing to their insufficient redox capacities. Z-scheme heterojunctions have therefore been considered as potential heterojunctions for the efficient degradation of organic pollutants due to their ability to maintain an adequate concentration of redox holes and electrons. In this paper, the preparation of Ag nanoparticles (NPs) decorated Z-scheme heterojunction photocatalyst composed of a CoAl-layered double hydroxide (LDH) and TiO2 is reported. This system was found to exhibit a superior photocatalytic activity in the degradation of the levofloxacin (LVFX) and Cr(VI). The Ag-CAT (12 h) catalyst exhibited the highest kinetic constant for the photocatalytic degradation of LVFX (K = 0.02588 min−1), and this value was 5.93 and 6.95 times greater than the corresponding values for TiO2 (K = 0.00476 min−1) and CoAl-LDH (K = 0.00372 min−1), respectively. A similar effect was also observed for the reduction of Cr(VI). Upon investigating the source of this excellent catalytic activity, it was found that the internal electric field in the CoAl-LDH/TiO2 heterojunction functions as a driving force to facilitate the efficient separation of photogenerated charge carriers, thereby generating holes and electrons with a high redox ability and realizing the effective elimination of a pharmaceutical and a heavy metal pollutant. Finally, the formation of internal electric field dominated Z-scheme CoAl-LDH/TiO2 heterojunction and the photocatalytic mechanism of Ag NPs decorated Z-scheme CoAl-LDH/TiO2 heterojunction photocatalyst was described in detail.

One-pot synthesis of S-scheme WO3/BiOBr heterojunction nanoflowers enriched with oxygen vacancies for enhanced tetracycline photodegradation

Construction of S-scheme heterojunctions that efficiently separate photogenerated electrons and holes is an emerging strategy for the development of high-efficiency performance photocatalysts for the photodegradation of organic pollutants. In this study, S-scheme WO3/BiOBr heterojunction nanoflowers enriched with oxygen vacancies (Vo) were synthesized for the first time via a one-pot hydrothermal method without the addition of surfactants. The XPS characterization of the WO3/BiOBr-Vo indicated the formation of internal electric field at the WO3/BiOBr interface, which facilitated charge separation and charge transfer. The superior ability of WO3/BiOBr-Vo to separate photoinduced electron–hole pairs was confirmed by photoluminescence and photocurrent responses. As a result, the optimal 25WO3/BiOBr-Vo photocatalyst decomposed 100% tetracycline after 50 min of visible light irradiation while pure BiOBr-Vo and WO3 decomposed less than 90% and 40% of tetracycline, respectively. The EPR analysis and free radicals trapping experiments found that the O2− was the main active species in the photocatalytic mechanism. The oxygen vacancies provided readily accessible reaction sites for the conversion of O2 to O2−. Toxicity assessment revealed that the aquatic toxicity of tetracycline was efficiently reduced after photodegradation. This study demonstrated a promising method for the development of high-performance photocatalysts based on band structure optimization and crystal defect engineering.

Efficient degradation of ciprofloxacin by Co3O4/Si nanoarrays heterojunction activated peroxymonosulfate under simulated sunlight: Performance and mechanism

The development of stable and efficient photocatalysts to activate peroxo monosulfate (PMS) is of great significance in water treatment, but it is still a major challenge. In this paper, Co3O4/Si nanoarrays (Co3O4/SiNWs) heterojunction is successfully synthesized through simple and effective approaches, and the peroxymonosulfate (PMS) assisted photocatalytic degradation system based on the Co3O4/SiNWs heterojunction under simulated sunlight is constructed for ciprofloxacin (CIP) degradation. The Co3O4/SiNWs-30/PMS system exhibits a high CIP photocatalytic degradation rate of 93.51% and a kinetic constant of 0.0474 min−1 in 60 min accompanied with good degradation stability. The appropriate energy band structure of Co3O4/SiNWs heterojunction allow the formation of internal electric field, resulting in the establishment of a typical Z-scheme charge transfer system. On the one hand, the formed Co3O4/SiNWs Z-scheme heterojunction can synchronously inhibit the recombination of photo-generated electron-hole (e--h+), which promotes the transfer of photogenerated carriers and improve the photocatalytic activity. On the other hand, photogenerated e- contribute to produce active radicals by activating PMS, and photogenerated h+ can also be directly used as active radicals, thereby realizing high-efficiency photocatalytic degradation. This work gives a good insight into the photocatalytic degradation of antibiotics in water.

S-Scheme/Type-1 heterostructure stimulated WO3/g-C3N4-WS2 ternary photocatalyst with improved charge transfer mechanism for full solar spectrum photocatalysis

Combination of liquid ultrasonication and facile hydrothermal approach were used for synthesis of novel highly efficient WO3/g-C3N4-WS2 ternary photocatalyst. The presence of noble metal free WS2 as cocatalyst induced localized surface plasma resonance (LSPR) and extended the light utilizing spectrum of the ternary composite towards the NIR. An electrochemical property reveals that it follows combined S-Scheme/Type-1 mode of changer transfer mechanism in the ternary. Transient photocurrent validated the excitation of charge carriers in the presence of light with 18.18% increases in photocurrent for ternary. Formation of internal electric field at the interface of heterojunction restricted the recombination rate. The reduction in the charge transfer resistance by the introduction of WS2 was established through LSPR effect. Pore size varies from 2 to 30 nm confirms mesoporous structure. Highest donor density of 4.24 × 1023 was found in WOCNS. This has significantly enhanced photocatalysing ability and established successful degradation of both MB and MO under the direct sunlight and artificial NIR light source. AQY of WOCNS composite was found to be 66.67% higher than pristine g-C3N4 in the NIR region. The dominance of reactive oxygen species (ROS) such as superoxide radicals (.O2-) and holes (h+) were primarily responsible for decomposition of MB and MO. The ternary exhibited high stability and reusability with a removal efficiency of 87% for up to 5th consecutive cycles. This study demonstrates the novel S-scheme/Type-1 strategy for harnessing full solar spectrum with application towards water purification and industrial wastewater treatment.

Defects and internal electric fields synergistically optimized g-C3N4−x/BiOCl/WO2.92 heterojunction for photocatalytic NO deep oxidation

In this work, g-C3N4−x/BiOCl/WO2.92 heterojunction with “N-O” vacancies was prepared using NaBiO3 and WCl6 as raw materials and non-metal plasma of WO2.92 grew in-situ on the surface of BiOCl, resulting in the enhanced photocatalytic NO deep oxidation. XPS tests and DFT calculation indicated the formation of internal electric fields from g-C3N4−x to BiOCl, BiOCl to WO2.92, which induced the transition from Ⅱ-Ⅱ-type to double Z-scheme hetero-structure. High separation efficiency, prolong lifetime and strong redox ability of photo-generated electron-hole pairs were simultaneously achieved due to the charge capture effect of defects and double Z-scheme mechanism. Therefore, g-C3N4−x/BiOCl/WO2.92 exhibited the significantly increased NO removal rates from 21.17% (BiOCl/WO2.92) and 36.52% (g-C3N4−x) to 68.70% and the main oxidation product of NO was NO3−. This study revealed that the carrier dynamics of heterojunction photocatalysts could be optimized by the synergistic effect of defects and internal electric fields to achieve photocatalytic NO deep oxidization.

Unexpected Photoinduced Room Temperature Magnetization in Bi2 WO6 Nanosheets.

The current investigation in magnetism in 2D materials offers new opportunities for studying spintronics at low dimensions. Here, reversible photoinduced room temperature magnetization in 2D Bi2 WO6 nanosheets is reported for the first time. Compared with the original state, the ultraviolet (UV)-illuminated Bi2 WO6 nanosheets show a yellow-green color change and significantly enhanced magnetic signals (saturated magnetization (Ms ) increased from 0.002 to 0.12 emu g-1 ). X-ray photoelectron spectroscopy (XPS) results show unexpected W reduction (W6+ to W5+ /W4+) and Bi oxidation (Bi3+ to Bi5+ ) upon UV illumination for the Bi2 WO6 nanosheets, indicating a photoexcited Bi to W charge transfer. Density functional theory (DFT) calculations indicate spontaneous spin polarization of the Bi2 WO6 nanosheets in the excited metastable state. Meanwhile, thicker Bi2 WO6 nanoplates or nanoparticles show no enhanced magnetic signals upon UV illumination. UV illumination of the thin Bi2 WO6 nanosheets can induce the formation of internal electric field (polarization), leading to structural deformation/lattice distortion (photostriction). The photoexcited electrons are trapped in the WO6 layers while the photogenerated holes are trapped in the Bi2 O2 layers, leading to spin polarization and enhance the magnetization. The research may bring some new insights in tuning the magnetic properties of 2D nanostructures.

Steering photo-excitons towards active sites: Intensified substrates affinity and spatial charge separation for photocatalytic molecular oxygen activation and pollutant removal

Bismuth oxybromide-based heterostructure has been constructed widely for various photocatalytic application. However, the function of the exposed facets in heterostructure still remains to be elucidated. Herein, we chemically implanted bismuth oxybromide nano-units with dominantly exposed (010) facets on indium vanadate particles to form composites. Results showed that the absorption range of visible light was extended due to the high photosensitivity of InVO4 and the charge transfer was also effectively expedited by the formation of internal electric field. Contrast experiments manifested that BiOBr with dominant (010) facets was more suitable than that with (001) facets to act as electron acceptor in InVO4/BiOBr heterojunction, because the open channels on (010) facets provided large accommodation space for organic pollutants. Thus, the generated superoxide radicals on BiOBr could annihilate the adsorbed pollutants rapidly. Moreover, the hierarchical core-shell structure provided large surface area to further intensify the affinity of InVO4/BiOBr composites to pollutants. Consequently, the hierarchical InVO4/BiOBr heterojunction exhibited excellent photocatalytic activity and could degrade 92.59% of ciprofloxacin (CIP) within 1 h under visible light. The reaction data were fitted with multiple models to investigate the whole reaction process. Furthermore, the impacts of various simulated actual factors on CIP adsorption and degradation were explored. The intermediates and possible degradation pathways were also illustrated through Liquid Chromatography-Mass/Mass Spectrometry (LC-MS). This work not only provide a facet engineering concept for heterojunction construction, but also help us to further understand the relationship between adsorption and photocatalytic degradation.

Crystallization, cyanamide defect and ion induction of carbon nitride: Exciton polarization dissociation, charge transfer and surface electron density for enhanced hydrogen evolution

Exciton polarization dissociation, charge transfer and surface electron density in photocatalysts are crucial for photocatalytic hydrogen evolution reactions (HERs). In this study, crystalline carbon nitride with cyanamide defect edges (crystalline CCN) was synthesized by one step polymerization of urea in the presence of KCl. The texture and electronic band structure of carbon nitrides could be facilely tailored by changing KCl dosage. The light absorption edge of crystalline CCN extended to 736 nm due to n→π* electron transition. The enhanced dielectric constants of crystalline carbon nitrides promoted exciton polarization dissociation. The small effective electron mass (me*) in crystalline CCN facilitated me* diffusion. The efficient separation of electrons and holes benefited the formation of internal electric field, showing an 8.56-fold promotion in electron transfer compared to pristine CN. Significantly, femtosecond time-resolved transient absorption demonstrated that the surface electron density on crystalline CCN was enhanced in the presence of salt ions (NaCl). As a result, crystalline CCN exhibited 14.9 times higher HER rate than pristine CN under visible light irradiation. The apparent quantum yield for H2 evolution on crystalline CCN reached to 42% at 420 nm and 9% at 500 nm. This study gets a comprehensive understanding of photocatalytic HERs using carbon nitride photocatalysts.