Bimetallic MOF PhotocatalystsTi atoms rapidly replace Zr atoms in UiO‐66‐NH2 crystal under microwave irradiation. The formed congenetic “shell‐core” structure and the introduced electron acceptor, ...Ti, enhance the photocatalytic nitric oxide (NO) removal. Furthermore, the synergy of NO photooxidation and subsequent NO2 adsorption not only removes NO efficiently in an environmentally friendly fashion, but also provides raw NO2 safely and economically to industry. More details can be found in article number 2207198 by Hesheng Yu, Zhongchao Tan, and co‐workers.
We present an approach to the noninvasive determination of the electron capacity of the intersystem pool of electron carriers in chloroplasts in situ. As apt experimental models, we used the leaves ...of Hibiscus rosa-sinensis and Tradescantia species. Electron paramagnetic resonance and optical response of P700 (the primary electron donor in Photosystem I) were applied to measuring electron transport in chloroplasts. Electron capacities of the intersystem electron transport chain (ETC) were determined from redox transients of P700 upon chromatic transitions (white light → far-red light). During the induction period, we observed the nonmonotonic changes in the number of electron equivalents in the intersystem ETC per P700 (parameter Q). In Hibiscus rosa-sinensis, the light-induced rise of Q from ≈2.5 (in the dark) to Q ≈ 12 was followed by its decrease to Q ≈ 6. The data obtained are discussed in the context of pH-dependent regulation of electron transport in chloroplasts, which provides the well-balanced operation of the intersystem ETC. The decay of Q is explained by the attenuation of Photosystem II activity due to the lumen acidification and the acceleration of plastoquinol re-oxidation as a result of the Calvin-Benson cycle activation. Our computer model of electron and proton transport coupled to ATP synthesis in chloroplasts was used to analyze the up and down feedbacks responsible for pH-dependent regulation of electron transport in chloroplasts. The procedures introduced here may be important for subsequent works aimed at defining the plastoquinone participation in regulation of photosynthetic processes in chloroplasts in situ.
•Method for determination of the intersystem electron capacity is developed.•We demonstrated non-monotonic dynamics of plastoquinone reduction/oxidation.•Computer model of electron and proton transport in chloroplasts is developed.
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•Ti3+ self-doped TiO2 microsphere with sea urchin like structure was synthesized.•The Ti3+ self-doping improved the activity for photocatalytic benzene oxidation.•The Ti3+ self-doping ...suppressed the recombination of electrons-hole separation.•The Ti3+ site on the TiO2 surface suppressed the build-up of byproducts.
Photocatalytic oxidation processes (PCO processes) are a promising technology for controlling the pollution of working environments, namely, the low concentrations of volatile organic compounds (VOCs) generated in industrial processes, and improving the efficiency of this process is an important issue. In this study, the photocatalytic oxidation of gas-phase benzene was carried out with TiO2 microspheres with a sea-urchin-like structure, and the effect of Ti3+ self-doping on the catalytic performance of TiO2 was investigated in detail. The structures and properties were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV–visible diffuse reflectance spectroscopy, electron spin resonance, scanning electron microscopy, and high-resolution transmission electron microscopy. Ti3+ ions were formed in TiO2 microspheres by heating under vacuum, which improved the catalytic performance of TiO2 for the complete oxidation of benzene to CO2 and CO. The photoelectrochemical measurements showed that the incorporation of Ti3+ into TiO2 microspheres reduced electron-hole recombination and increased the light absorption capacity, which contributed to improving the photocatalytic activity. In situ FTIR spectroscopic studies revealed that in the benzene oxidation process, Ti3+ self-doped TiO2 microspheres suppressed the formation of strongly bound byproduct compounds on the TiO2 surface, which affected the rate of benzene oxidation. Thus, the Ti3+ self-doped TiO2 microspheres are effective catalysts for efficient use of UV light and suppression of catalyst deactivation during benzene oxidation.
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•Mimicking porphyrin structure, M−Nx single-atom sites act as triplet sensitizing sites.•With the assistant of M−Nx, carbon nitride process long-lived lifetime for catalysis.•Metal ...species (Fe0) promote electron transfer and inhibit triplet energy transfer.
Polymeric carbon nitride materials show intriguing prospects in numerous light-to-energy conversion applications, but seldom studies focus on their triplet energy transfer, leading to the insufficient lifetime for the photochemical process. Inspired by the porphyrin molecular photocatalyst, single-atom sites (Fe-N4) as triplet sensitizing sites were fabricated in g-C3N4 for the preparation of Fe-g-C3N4, which processes a long-lived triplet emissive state (τPH = 4.93 μs). But under realistic condition for the large-scale production of catalyst, single atoms are inevitable to sinter, resulting in the formation of other metal species. Therefore, the photooxidation of 1,5-dihydroxynaphthalene (1,5-DHN) and the photocatalytic E-Z Isomerization of stilbene were selected as the model reactions to evaluate the influence of various Fe species on the triplet energy transfer. It was found that Fe-N4 sites promote the triplet energy transfer process, while Fe nanoclusters (Fe0) promote the electron transfer and inhibit triplet energy transfer. This finding provides guidance for the rational design of photocatalysts to efficiently improve triplet energy transfer process and its application.
Nitrate is an important raw material for chemical fertilizers, but it is industrially manufactured in multiple steps at high temperature and pressure, urgently motivating the design of a green and ...sustainable strategy for nitrate production. We report the photosynthesis of nitrate from N2 and O2 on commercial TiO2 in a flow reactor under ambient conditions. The TiO2 photocatalyst offered a high nitrate yield of 1.85 μmol h−1 as well as a solar‐to‐nitrate energy conversion efficiency up to 0.13 %. We combined reactivity and in situ Fourier transform infrared spectroscopy to elucidate the mechanism of nitrate formation and unveil the special role of O2 in N≡N bond dissociation. The mechanistic insight into charge‐involved N2 oxidation was further demonstrated by in situ transient absorption spectroscopy and electron paramagnetic resonance. This work exhibits the mechanistic origin of N2 photooxidation and initiates a potential method for triggering inert catalytic reactions.
In situ and ultrafast time‐resolved spectroscopic characterization and computational simulations were employed to elucidate the role of O2 in promoting N2 dissociation through a low‐energy pathway evolving from *OxNy to an *ON intermediate. A TiO2 photocatalyst exhibited outstanding N2 photofixation performance with a solar‐to‐nitrate energy conversion efficiency up to 0.13 %.
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•A new light-controlled nanozyme with tunable oxidase-like activities is presented.•Its activity can be regulated by the concentration ratio of carbon dots and Ce3+ ions.•It can ...perform optimally at neutral pH values for catalytic oxidation of TMB.•Ce3+ ions act as catalytic mediators to break pH-dependent activity of carbon dots.
Industrial and medical applications of most nanozymes are often limited by their pH-dependent activities as well as by weak response to external stimuli. Here we report a light-controlled nanozyme possessing tunable oxidase-like activities without incurring the burden of pH effects. This nanozyme comprises carbon dots (CDs) and Ce3+ ions and its activities can be regulated with rational design of their concentration ratio. Unlike previously reported nanozymes, yet it can perform optimally at neutral pH values for catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). We find that its unique attribute originates from pH-dependent ability of CDs to reversibly switch from Ce3+ to Ce4+ under visible light irradiation. Therefore, our presented nanozyme can be applied in real environment and be simultaneously remotely-controlled by visible light.
Abstract
The conversion of photocatalytic methane into methanol in high yield with selectivity remains a huge challenge due to unavoidable overoxidation. Here, the photocatalytic oxidation of CH
4
...into CH
3
OH by O
2
is carried out on Ag-decorated facet-dominated TiO
2
. The {001}-dominated TiO
2
shows a durable CH
3
OH yield of 4.8 mmol g
−1
h
−1
and a selectivity of approximately 80%, which represent much higher values than those reported in recent studies and are better than those obtained for {101}-dominated TiO
2
. Operando Fourier transform infrared spectroscopy, electron spin resonance, and nuclear magnetic resonance techniques are used to comprehensively clarify the underlying mechanism. The straightforward generation of oxygen vacancies on {001} by photoinduced holes plays a key role in avoiding the formation of •CH
3
and •OH, which are the main factors leading to overoxidation and are generally formed on the {101} facet. The generation of oxygen vacancies on {001} results in distinct intermediates and reaction pathways (oxygen vacancy → Ti–O
2
•
→ Ti–OO–Ti and Ti–(OO) → Ti–O
•
pairs), thus achieving high selectivity and yield for CH
4
photooxidation into CH
3
OH.
Photooxidation aging, hygrothermal aging, and hot‐air aging are carried out on atactic polystyrene (aPS) samples formed by injection molding. It is interesting that microcrystals of atactic ...polystyrene are only found in photooxidation aging. This work proposes that high molecular weight atactic polystyrene can crystallize under photooxidation aging. It is a good addition to the research on the aspect of crystallization of atactic polystyrene.
In this report, high molecular weight atactic polystyrene is studied. It is found that microcrystals of atactic polystyrene exist only under the effect of photooxidation aging, and the molecular weight of polystyrene after aging is above 105. This nicely complements the research on the crystallization of atactic polystyrene.
Five new Ru(II) polypyridyl complexes bearing N-(arylsulfonyl)-8-amidoquinolate ligands and three of their biscyclometalated Ir(III) congeners have been prepared and employed as photocatalysts (PCs) ...in the photooxidation of benzylamines with O 2 . In particular, the new Ru(II) complexes do not exhibit photoluminescence but they harvest visible light efficiently and are very stable in solution under irradiation with blue light. Their non-emissive behavior has been related to the low electrochemical energy gaps and rationalized on the basis of theoretical calculations (DFT analysis), which predict low S 0 ← T 1 energy values. Moreover, the Ru(II) complexes, despite being non-emissive, display excellent activities in the selective photocatalytic transformation of benzylamines into the corresponding imines. The presence of an electron withdrawing group (-CF 3 ) on the arene ring of the N-(arylsulfonyl)-8-amidoquinolate ligand improves the photocatalytic activity of the corresponding photocatalyst. Furthermore, all the experimental evidences, including Transient Absorption Spectroscopy measurements suggest that singlet oxygen is the actual oxidant. The Ir(III) analogues are considerably more photosensitive and consequently less efficient photosensitizers (PSs).
We report on the synthesis, characterization and application to water photo-dissociation of micrometer-long self-ordered TiO2 nanorod (TDNR) mats, surface sensitized by deposition of cobalt ...dodecahedral Zeolitic Imidazolate Framework (ZIF-67) coatings. TDNR mats have been grown over glass/FTO substrates from titanium (IV) butoxide, by using a solvothermal procedure at 150 °C. Homogeneous micrometer-thick mats of ~120 nm wide TDNRs (surface density ~15–20 nanorods per μm2) have been obtained. The TDNR mats have been impregnated by crystalline coatings of ZIF-67 MOF. Four different photoelectrodes, containing different amounts of ZIF-67, have been prepared and characterized. X-ray photoelectron spectroscopy analysis revealed that the oxidation state of Co is CoII. The presence of MOF at the surface of TDNRs has been found to greatly impact the optical properties of TiO2: light absorption is shifted to the Vis region. The apparent band-gaps of the composites were determined from Tauc's plots. The photoelectrodes have been used as photoanodes for water photooxidation in Na2SO4 aqueous solutions. I–V curves have been measured under chopped illumination conditions by linear sweep voltammetry (LSV), under Vis and UV–Vis irradiation. The dynamics of charge transfer at the interface has been investigated by photoelectrochemical impedance spectroscopy (PEIS). In the dark, all photoelectrodes present a capacitive behavior with a high impedance. Under Vis irradiation, only one time constant is observed, and all photoelectrodes impedances are found in the 105–106 Ω cm2 range. Such values are consistent with the observed photocurrents. Under UV–Vis light, PEIS spectra appeared flattened and therefore the data have been fitted with two time constants, with a model considering the presence of surface states at the interface. The photoanode presenting the highest photocurrent (16 h of MOF growth) also displays the lowest value for the charge transfer resistance from trap states, clearly evidencing the role of the MOF as a surface co-catalyst with a beneficial effect for water splitting. The presence of MOF at the surface has been also found to increase the rate of charge recombination. The observed photocurrent has been found to be a result of the dynamic interplay between charge transfer and recombination microscopic processes.
•Novel nano-architectured water splitting photo-anodes are described.•TiO2 nanorod mats surface sensitized by cobalt ZIF-67 have been synthesized.•Polarization curves have been measured under chopped illumination conditions.•Impedance spectroscopy has been used to analyze charge transfer mechanism.•An analysis of the water photo-oxidation mechanism is provided.
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