查看更多>>摘要：In virtue of the pliable structure and ample pendent amine groups, the metal-free graphic carbon nitride (g-C3N4, abbreviated as CN) in two-dimensional (2D) morphology could be covalently modified by organic materials to modulate its photoelectrical characteristics. In this work, CN is covalently wrapped by a 2D Schiff-base covalent organic framework (COF, denoted as TMP), which is composed of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT), melem and 1,3,5-triformyl phloroglucinol (TP), by means of "one-pot " solvothermal method with a cocoon-like morphology presented (CN/TMP). Given the significant distinction of charge densities between the two constituent units, viz., melem and TAPT, the resultant acceleration of the intramolecular charge transfer (ICT) within the TMP shroud endows the formed integrate with a significantly raised charge delivery and lowered band gap energy (E-g) in comparison to a structure-analogous COF (TM) incorporated hybrid, CN/TM, in which the TAPT monomer is not involved in the TM COF construction. The photocatalytic water-splitting evaluation indicates CN/TMP conducted photocatalysis could provide the hydrogen (H-2) production of 102.88 mu mol.h(-1), about 5.6 and 11.6 times greater than that of CN/TM and CN, respectively. Our modulation strategy at molecular level proffers a new opportunity for the construction of the carbon nitride based hybrids and the regulation in their photoelectric behaviors.
查看更多>>摘要：Developing efficient and stable OER catalysts is conducive to improving hydrogen production efficiency and achieving "carbon neutrality " goal. Herein, a CoNi nano-alloys modified yolk-shell carbon cage (CoNi/NC-YS) catalyst was synthesized through a green synthesis method, which shows an outstanding OER activity with a low overpotential of 292 mV at 10 mA.cm(-2), and a robust OER catalytic stability. The experimental and density functional theory (DFT) results demonstrate that the hydrophilic yolk-shell CoNi/NC-YS catalyst with large specific area contributes to exposing more active sites, and increases the reaction contact area between catalysts and electrolyte. Meanwhile, CoNi nano-alloys can regulate the electronic configuration of CoNi/NC-YS catalyst and optimize Gibbs free energies for water adsorption, accelerating OER process in alkaline media and showing an outstanding OER performance. This work can provide a low-cost and green strategy to construct nano-alloys modified yolk-shell OER catalysts for renewable energy systems.
查看更多>>摘要：As a typical carcinogenic phenolic environmental pollutant, hydroquinone (HQ), its effective catalytic conversion is particularly urgent for environmental protection. However, the development of low-cost, high-efficiency catalysts still faces many challenges. Furthermore, the mechanism for efficient catalysis has not been established. In this paper, a trace amount of Pd-supported 3D urchin-like Pd/W18O49 composite in an aqueous solution was reported as a high-quality catalyst for the H2O2 catalytic oxidation of hydroquinone (HQ) to benzoquinone (BQ) with a turnover frequency (TOF) of 1750 h(-1), exceeding commercial catalyst. Through experiments combined with density functional theory (DFT) calculations analysis, this excellent catalytic effect is mainly attributed to the existence of an electronic induction effect between W18O49 and Pd nanoparticles (NPs). Meanwhile, the abundant oxygen vacancies on the surface of W18O49 can stabilize the & BULL;OH radicals generated from the decomposition of H2O2, thus promoting the breakage of O-O bonds to generate more center dot OH radicals and achieve an effective oxidation reaction. In addition, the influencing factors such as catalyst and HQ concentration, solution pH, solvent, various inorganic and organic interferences were comprehensively investigated. The 3D urchin-like Pd/W18O49 catalyst also showed an excellent effect on the catalytic oxidation of HQ derivatives with high TOFs.
Mendoza-Nunez, E. M.Solis-Garcia, A.Ortiz-Dominguez, C.Soto-Arteaga, C. E....
13页
查看更多>>摘要：This work reports the synthesis and catalytic application of binary Al2O3-Y2O3 (AlY-x) mixed oxides varying the Y2O3 wt% content (with x = 0 %, 25 %, 50 %, 75 %, and 100 %) prepared by hydrothermal treatment. For AlY-0, urchin-like structures composed of nanobelts and nanorods clearly showed the gamma-alumina phase. The AlY-25, AlY-50, and AlY-75 exhibited the formation of nanospheres and microspheres with homogeneous compositions. The surface analysis by XPS revealed the presence of carbonates in the yttrium content materials and a slight Al enrichment in the AlY-25 and AlY-50 samples. Our catalytic experiments demonstrate that changing the surface acid/base properties and tuning the yttria content can induce modifications in the structural and electronic properties, conduction character, morphology, and especially on the conversion and selectivity of 2-propanol transformation. The mechanism involved in the different pathways for the transformation of 2-propanol was revised under the light of FTIR in-situ reaction analysis, thermo-conductivity chromatography, and multidimensional gas chromatography.
查看更多>>摘要：Reasonable construction and engineering of optimal hierarchical photocatalysts have garnered great attention in terms of promoting CO2 photoreduction into fuel production. Herein, we introduce a novel 3D O-doped g-C3N4/N-doped Nb2O5 (OCNNb) S-scheme heterojunction fabricated using control of each material's surface charge-induced heteroaggregation for photocatalytic CO2 reduction (PCR). The optimized sample converts CO2 with substantially greater rates (the sum production rate of CO and CH4) than the blank control, i.e., O-doped g-C3N4 (OCN) and N-doped Nb2O5 (NNBO). The enhanced photocatalytic efficiency can not only be ascribed to the prevention of photogenerated charge carrier recombination mediated by the S-scheme heterojunction but also to the high specific surface areas and abundance of active sites. In the meantime, work function measurement, in situ irradiated, X-ray photoelectron spectroscopy and electron paramagnetic resonance (EPR) studies confirm the S-scheme photogenerated charge transfer mechanism. This study offers a useful approach for fabricating extremely effective heterojunction photocatalysts to convert solar fuels.
查看更多>>摘要：The interfacial electron modulation of electrocatalyst is an effective strategy to realize the oxidation of organic chemicals. Here, a heterojunction (CoP-CoOOH) is prepared via a modulating electron density between interfaces for 5-hydroxymethylfurfural (HMF) oxidation to 2,5-furanedioic acid (FDCA) in high concentration. Density Functional Theory (DFT) shows that heterojunction increased efficient charged active centers, enhanced the adsorption of the reactant on the surface of electrocatalyst, and improved the HMF oxidation reaction (HMFOR) activity. The electrolyzer using CoP-CoOOH as cathodic evolution H-2 and anodic HMFOR requires only voltage of 1.42 V. Additionally, the diffusion limitation of the reaction is overcome via coupling with the flow reactor, which further improved the HMFOR efficiency. Although the HMF concentration is 150 mM, the Faraday efficiency of HMF and the selectivity of FDCA in the flow reactor are 98.2 % and 99.4 %, respectively.
查看更多>>摘要：Here, we provide an in-depth understanding of the catalytic mechanism of sodium for the carburization of alpha-Fe catalyst by C2H4 in contrast to traditional CO through an approach combing in situ XRD and molecular orbital theory, considering the carburization of iron-based catalyst to active iron carbides is a prerequisite step to display activity in CO/CO2 hydrogenation. In situ XRD experiments show that sodium can trigger the carburization of alpha-Fe by CO and accelerate the accumulation of carbon-rich iron carbides, due to the enhanced electron back-donation from d band in Fe surface to 2 pi* orbitals in CO, thereby facilitating the dissociation of CO and the carburization by CO. Nevertheless, sodium shows a contrary effect on the carburization of alpha-Fe under C2H4, due to the significant increase of the total dissociative energy, thereby facilitating the desorption instead of dissociation of C2H4 on Fe surface, finally inhibiting the carburization.
查看更多>>摘要：The precise size-controlled formation of palladium (Pd) nanoclusters with size-dependent catalytic activity was achieved through a cage confinement strategy. In this process, three typical porous organic cages (POCs) with gradually decreasing cavity diameters were used as encapsulation carriers. A series of Pd nanoclusters-based catalysts with corresponding Pd cluster sizes of 0.73, 0.68, and 0.43 nm, respectively, was effectively fabricated by confining the Pd nanoclusters in size-adjustable cavities. The obtained Pd@POCs nanocatalysts exhibited excellent crystallinity, high stability, fascinating morphological characteristics, and superior catalytic hydrogenation performance. Especially, the size-dependent catalytic performance toward hydrogenation of 4nitrophenol and semi-hydrogenation of alkyne compounds was demonstrated by experimental results and theoretical calculations. The prepared Pd(1.71%)@FT-RCC3 catalyst with the smallest Pd cluster size of about 0.43 nm showed the best catalytic performance. This study promotes a better understanding of size-dependent catalysis and provides a new strategy for the fabrication of customized nanocatalysts.
Wong, Kien TiekChoong, Choe EarnNah, In WookKim, Sang-Hyoun...
15页
查看更多>>摘要：A major challenge faced by most systems is the dissociation of O -O bonding on H2O2 by subsequent electron (e-) reduction. This study investigates interfacial charge transfer by manipulating e- flows through a deflexed band potential on polarized piezoelectric BiFO3 (BFO). The H2O2 accumulation via coupling with the photocatalyst BiOCl/BiVO4 (BCV) was highly effective since the Schottky barrier height (SBH) formed within the heterojunction composite shifted according to the surface polarity of BFO. Additionally, the constant alternating surface charge on BFO, reduced the SBH, forcing the photoexcited e- to flow from BCV -> BFO for effective H2O2 production, while restricting decomposition of H2O2 during downshifted band potential (positive surface) as high SBH discontinuing the electrons flow from BCV -> BFO. The high interfacial charge transfer resistance (Rct) was also critical for H2O2 accumulation, since it is unfavorable for H2O2 dissociation (H2O2/.OH, +0.39 V) despite the presence of a high band potential (+0.16 eV) on the opposite surface's upshifted band. The formation rate (kf: 1.13 mu mol L-1 min(-1)) of H2O2 was calculated much higher than decomposition rate (kd: 0.01 min(-1)). Additionally, the RRDE results indicated favorable 2e- transfer with > 90 % selectivity for H2O2. Results from ESR DMPO-.OH abduction and atrazine degradation show an insignificant concentration of .OH has been produced. This work provides an effective strategy to regulate semiconductors' surface junction by piezoelectric polarization for selective H2O2 generation.
查看更多>>摘要：The construction of S-scheme heterojunction catalysts is promising for efficient photocatalytic hydrogen production, but the conscious modulation of S-scheme charge transfer has remained largely underdeveloped. Herein, P and C modified Co2P/black TiO2 S-scheme heterojunction photocatalyst (Co2P/PC-b-TiO2) is prepared by pyrolyzing a mixture of cobalt phosphonate and TiO2 under H2 atmosphere. The in situ formed P and C dopants can not only enhance the ratio of surface active O species to bulk O defects but also inhibit anatase-to-rutile phase transformation, thereby ensuring the high intrinsic activity. More importantly, the S-scheme heterojunction between PC-b-TiO2 and Co2P is modified by the incorporation of P and C, wherein the intimately coupled heterointerface and strong internal electric field can accelerate charge separation and migration and optimize the available redox potential. Accordingly, Co2P/PC-b-TiO2 displays dramatically ascendant photocatalytic hydrogen evolution performance and outstanding stability. This study provides guidance for elaborately modifying Sscheme heterojunctions through heteroatom doping and heralds a new paradigm for engineering advanced heterojunction catalysts.
NSTL
Elsevier