查看更多>>摘要：The construction of metal-organic frameworks (MOFs) with hierarchical pores is of great importance for the photocatalytic oxidation (PCO) of gaseous BTXS (benzene, toluene, xylenes and styrene) pollutants with large molecular size, but it is still challenging. Herein, by adjusting the ratio of anions (NO3- and Cl-) in the metal precursors, hierarchically porous MIL-100(Fe) MOF/MOX homojunctions were obtained through a one-pot solvothermal method. The existence of both micro- and mesopores (2-10 nm) made the active sites more accessible to guest molecules. The formation of MOF/MOX homojunctions promoted the separation of electronhole pairs. Additionally, the coordinatively unsaturated acidic Fe-3-O sites facilitated the capture of BTXS molecules and participated in the PCO process through the conversion between Fe(III) and Fe(II). The MIL-100(Fe) homojunctions showed improved performance towards the PCO of BTXS (over 80% for xylenes and styrene) compared with the crystalline or xerogel counterparts and exhibited great potential in the PCO of aromatic air pollutants.
查看更多>>摘要：2D (two-dimensional) covalent organic frameworks (COFs) have recently emerged as versatile photoactive functional materials. Herein, three 8-ketoenamine linked 2D COFs were assembled with 2,4,6-triformylphloroglucinol (Tp) and 4,7-bis(4-aminophenyl)-2,1,3-benzothiadiazole (BTD) as the building blocks at 150, 120, and 25 degrees C respectively, leading to Tp-BTD-150, Tp-BTD-120, and Tp-BTD-25. In particular, the facile synthesis at 25 degrees C afforded Tp-BTD-25 that featured superior activity for the photocatalytic selective aerobic oxidation of benzylamine to the other two assembled at higher temperatures. Most importantly, both the stability and activity of Tp-BTD-25 photocatalyst were augmented with exogenous 5 mol% TEMPO (2,2,6,6-tetramethylpiperidine-Noxyl) to ease the transfer of electrons and protons during the oxidation of benzyl amines. Preeminently, the selective aerobic oxidation of benzyl amines into imines was established by cooperative photocatalysis of TpBTD-25 with TEMPO irradiated by blue LEDs (light-emitting diodes). This work underscores that crystalline 2D COFs via facile synthesis can cooperatively work with a redox mediator to steer photocatalytic selective reactions.
查看更多>>摘要：In this study, the performance of periodate (PI) on sulfadiazine (SDZ) degradation was evaluated using coagulation solid waste fabricated catalyst (CWBC), obtained by simple pyrolysis. SDZ effectively underwent 98.94% remove within 90 min in the CWBC/PI system. Electron transfer was the predominant mechanism due to the development of an electronic cycle among SDZ, CWBC and PI, where the O-2(center dot-), PFRs, and the reactive iodine species had minor roles. Density functional theory calculations identified that Fe and N could change the electron configuration and break the chemical inertness of carbonaceous material. As a result, electrons on the carbon matrix of CWBC are inclined to travel through the formed Fe-O covalent bond to PI. Further analysis demonstrated that SO42-, humic acid (HA), as well as anoxic conditions greatly facilitated SDZ degradation. This study provides a facile protocol for converting coagulation waste to an efficient catalyst and provides fundamental insights into the degradation mechanisms of micropollutants by activating PI.
Serrano, David P.de la Pena O'Shea, Victor A.Collado, LauraRenones, Patricia...
11页
查看更多>>摘要：The development of sustainable processes for CO2 reduction to fuels and chemicals is one of the most important challenges to provide clean energy solutions. The use of sunlight as renewable energy source is an interesting alternative to power the electron transfer required for artificial photosynthesis. Even if redox sites are mainly responsible for this process, other reactive acidic/basic centers also contribute to the overall reaction pathway. However, a full understanding of the CO2 photoreduction mechanism is still a scientific challenge. In fact, the lack of agreement on standardized comparison criteria leads to a wide distribution of reported productions, even using the same catalyst, which hinders a reliable interpretation. An additional difficulty is ascertaining the origin of carbon-containing products and effect of surface carbon residues, as well as the reaction intermediates and products under real dynamic conditions. To determine the elusive reaction mechanism, we report an interconnected strategy combining in-situ spectroscopies, theoretical studies and catalytic experiments. These studies show that CO2 photoreduction productions are influenced by the presence of carbon deposits (i.e. organic molecules, carbonates and bicarbonates) over the TiO2 surface. Most importantly, the acid/base character of the surface and the reaction medium play a key role in the selectivity and deactivation pathways. This TiO2 deactivation is mainly initiated by the formation of carbonates and peroxo- species, while activity can be partially recovered by a mild acid washing treatment. We anticipate that these findings and methodology enlighten the main shadows still covering the CO2 reduction mechanism, and, most importantly, provide essential clues for the design of emergent materials and reactions for photo(electro)catalytic energy conversion.
查看更多>>摘要：As a renewable energy source, hydrogen production from biomass pyrolysis is one of the effective ways to promote global sustainable development. Herein, the inherent Al foils and typical LiCoO2 cathodes in spent lithium ion batteries are jointly employed as the catalyst to reform sawdust pyrolysis gas to produce hydrogenrich synthesis gas. It is the introduction of Al element that triggers the in-situ atomic replacement reaction to immobilize volatile lithium, thereby inducing the formation of a similar Li-CO2 battery system, which efficiently converts CO2 into CO. Furthermore, a new adsorption-enhanced in-situ-assembled porous structure has been discovered and proved to obtain similar to 95% surface vacancy oxygen content and various hydrogen evolution sites. Eventually, the yields and volume fractions of H-2 are 11.31 mmol/g and 65.79%, respectively, and the purity of syngas (H-2 +CO) reaches 91.82%, which verify its excellent performance in hydrogen reforming and CO2 conversion.
查看更多>>摘要：MXenes, 2D transition metal carbides/nitrides, have been demonstrated as promising platform for fabricating novel composites with interesting photo-/electrochemical properties. It is desirable to gain insights into the reactivity of MXenes, enabling the controllable transformation of MXenes. Here, a one-pot hydrothermal synthesis method of MXene-based photocatalyst is validated by harnessing the reducibility of Nb2CTx MXene. The origin of reducibility of Nb2CTx during the hydrothermal oxidation process was demonstrated as the active hydrogen produced from the water splitting in the presence of Nb2CTx , which reduced Ru3+ in situ to Ru nanoparticles on Nb2O5 nanowires derived from Nb2CTx. Compared with the traditional photo-deposition method, the chemical valance of the noble metal Ru/Pt obtained by the one-pot synthesis method was closer to the metal state, which reduced the charge transfer resistance by 82.5%. It led to the photocatalytic hydrogen production of 10.11 mmol.h(-)(1).g(-1) with 41.25% apparent quantum yield at 313 nm.
查看更多>>摘要：At present, it is still a challenge to develop ozone decomposition catalysts with high efficiency and high humidity resistance. Herein, a series of spinel (Mn,Co)(3)O-4 catalysts are synthesized by coprecipitation method. Compared with the Mn3O4 and Co3O4 analogues, the obtained (Mn,Co)(3)O-4 has Co-CoIII(IIx) acceptor-defect and Mn-MnII(IIIx) donor-defect, which could contribute to the electron transfer between catalyst and ozone, accelerating ozone decomposition. Importantly, the in-situ Raman spectra of Mn3O4 shows the accumulation of peroxide species (O-2(2-)) inferring that the decomposition of O-2(2-) is the rate-determining step. On the other side, the reaction of the atomic oxygen with ozone would be rate-determining for Co3O4, as revealed by the low efficiency but no O-2(2-) signal. However, the synergy of Mn and Co in (Mn,Co)(3)O-4 accelerates both the rate-determining steps obtaining high efficiency, which provides a new idea to develop catalysts in ozone elimination.
查看更多>>摘要：Plasmonic photocatalysis has emerged as a promising solution for global energy crisis and environment pollution by facilitating wide ranging chemical transformations using photons in a broad region of solar spectrum. Despite numerous successful examples on improvement of electron-driven photochemistry, effective utilization of plasmonic hot holes is a long-standing challenge due to their ultrafast relaxation and short lifetime. Herein, we report that the reactivity of plasmonic hot holes can be greatly enhanced by a novel hot hole trapping strategy. We demonstrate a new concept of a metal-adsorbate interfacial structure that can be in situ constructed on gold (Au) surface in the presence of molecular hydrogen (H2) under plasmonic excitation, where the key is to employ an electron-filled antibonding state hybridized by H1s and Au5d as a localized "trap" to improve utilization efficiency of plasmonic hot holes. This interfacial structure is evidenced by light-induced H2 spillover and d-band model analysis. The prolonged lifetime and preserved oxidation power of plasmonic hot holes was evidenced by superior photocatalytic activity for methylene blue (MB) degradation in the presence of H2 which was accelerated by over 5 times. In addition, FTIR coupled with CO molecular probe reveals that the physical location of hole trapping are low coordinated positions sites on Au nanoparticles. These findings could provide an innovative pathway to increase utilization efficiency of hot holes for visible-light-driven photocatalysis applications.
查看更多>>摘要：Herein, a g-C3N4/PDI-g-C3N4 homojunction has been fabricated for piezo-photocatalytic atrazine removal and exhibited better performance than individual photocatalysis or piezocatalysis. The introduction of PDI induces the 7C-7C interaction facilitating electrons migration, and twists the g-C3N4 plane into a more polar porous structure with enhanced piezoelectricity. The homojunction facilitates the photoelectron transfer at the g-C3N4/PDI-gC3N4 interfaces. The photoelectricity and the piezoelectricity of g-C3N4/PDI-g-C3N4 were assessed. The finite element simulation showed that the porous structure of the g-C3N4/PDI-g-C3N4 is essential to the enhanced piezoelectricity. Astonishingly, the piezo-photocatalytic atrazine degradation rate under an optimized condition (pH=2.97) reached 94% within 60 min. Moreover, the g-C3N4/PDI-g-C3N4 homojunction produced 625.54 mu M H2O2 during the one-hour piezo-photocatalysis. Given the quenching experiments, reactive species detection and the electronic band of g-C3N4/PDI-g-C3N4, the piezo-photocatalytic mechanism has been proposed. In addition, the degradation pathways and the reduced intermediates toxicity intermediates of atrazine have been investigated.
查看更多>>摘要：In pursuit of finding alternatives to Pt for O-2 reduction reaction (ORR), biomass-based catalysts are promising candidates because of their low prices and comprehensive sources that just compensate for the drawbacks of Pt. However, it is difficult to determine unambiguously structure-function correlations of biomass-based catalysts due to their complex structures. Moreover, biomass-based metal-free ORR electrocatalysts often suffer from poor mass transport and pH applicability. Hence, tuning structural variables specifically, improving mass transport within porous domains, and achieving pH-universal catalytic activities are key to optimization of metal-free ORR electrocatalysts derived from biomass. In this study the 'basic bathing' method is proposed for precise control over structural variables of nitrogen-doped metal-free ORR electrocatalysts that originate from staple waste biomass-wheat straw. The basic bathing makes use of the fact that KOH can result in a series of physicochemical changes within lignocellulosic biomass and thereby re-proportion pore width distributions of synthesized materials. Under the action of basic bathing, the optimal electrocatalyst having the largest mesopore volume and the equal distribution of nitrogen species is superior in terms of pH-universal ORR electrocatalytic activity when compared to its non-basic-bathing counterparts. The structure-function analyses, benefiting from the specific tuning of mesopores by the basic bathing, demonstrate the linear relations between mesopore volumes and limiting current densities irrespective of pH. Furthermore, the density functional theory (DFT) calculations indicate the synergistic effects of pyridinic, pyrrolic and graphitic nitrogens at a 1:1:1 atomic ratio contribute to the decreased overpotential requirement. Taken together, the reproducible results provide compelling evidence for the importance of mesopores and nitrogen species distributions in enhancing the pH-universal ORR performance. In a broader context, the basic bathing is truly inspirational for niche exploitation of biomass for future energy technologies.
NSTL
Elsevier