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：Methane is the main component of natural gas, and the latter is a clean natural resource with an abundant reserve and wide distribution. Elemental sulfur is both naturally available on the earth and being artificially generated as a recalcitrant solid waste in chemical processes. The co-utilization of elemental sulfur and methane is thus of economic and environmental benefits. Here, a new catalytic route for elemental sulfur-assisted methane activation is demonstrated over metal-loaded zeolite catalysts at a low temperature of 400 degrees C. Over 10% methane conversion can be achieved even after the catalyst is recycled five times, and the selectivity is well controlled, generating over 90% C-2-C-4 hydrocarbons as the main products. Control experiments are employed to demonstrate the strategy developed for catalyst design, and a series of verification experiments accompanied by various catalyst characterizations are also performed to elucidate the involved reaction mechanism. The results are further substantiated by theoretical calculations for proposing the possible reaction network. It is suggested that the Langmuir-Hinshelwood surface reaction mechanism might be followed, in which elemental sulfur and methane are both adsorbed over the catalyst surface in a competitive way. When methane activation is triggered and significantly enhanced in the presence of sulfur, both surface reaction and gas-phase reaction can proceed, generating sulfides as complete oxidation products and light hydrocarbons as partial oxidation products, respectively. As a result, the product distribution can be well modulated by the adsorption properties of the charged catalyst. This process provides a transformative cost- and energy-effective way for the co-utilization of two low value-added feedstocks with unique advantages in the natural gas and petroleum industry.
查看更多>>摘要：This study investigates the binary role of Ti3+ self-doped TiO2 nanotubes (bl-TNA) as an anode as well as a cathode in the photoelectrochemical (PEC) oxidative treatment of organic contaminants. Compared to the Ti cathode-based asymmetric system, the symmetric PEC system with Janus bl-TNA photoelectrodes demonstrated higher interfacial charge transfer, photoresponsive activity, and kinetic constant for bisphenol-A (BPA) degradation. The bl-TNA photocathode enhanced the formation of radicals by providing additional reaction sites for photocatalytic reactions and cathodic peroxydisulfate (PDS) activation. Additionally, the rate constant ratio for BPA degradation between the anode and cathode in the symmetric system changed from 7.5:1-1.3:1 under PEC and PEC/PDS conditions, indicating that PDS addition enhanced the photoactivity of the electrodes, with a higher rate at the cathode. Finally, only 2.4% performance decline was observed after 64 h with the periodic polarity reversal operation, demonstrating the long-term stability of the proposed PEC system.
查看更多>>摘要：h-BN-based electrocatalysts with low-cost and high efficiency have a great potential for electrochemical nitrogen reduction reaction (NRR). The carbon-doped boron nitride (C-BN) nanosheets are proposed as the excellent metal-free electrocatalysts for converting nitrogen to ammonia (NH3). In 0.1 M Na2SO4 solution, it obtains NH3 yield of 44.59 +/- 1.79 mu g h-1 mgcat -1 at - 0.9 V vs reversible hydrogen electrode (RHE), with a high faradaic efficiency (FE) of 13.27 +/- 0.42 % at - 0.7 V vs RHE, and an outstanding electrochemical durability. Density functional theory (DFT) calculations reveal that carbon-doping dramatically reduces the band gap to 1.40 eV and induces charge accumulation on carbon atom to facilitate N2 adsorption. The synergistic interaction of C and B atoms at the double-active-site of C-BN significantly decreases the energy barrier (from *NH-NH to *NH-NH2) for the potential-determining step. The results confirm that C-BN has the potential as an efficient metal-free NRR electrocatalyst in neutral media.
查看更多>>摘要：Ti3+ self-doped Fe2O3/TiO2 ultra-thin nanoflakes have been fabricated on Ti-substrate by a facile hydrothermal route. The high solar light harvest by Ti3+ and oxygen vacancies makes Ti3+ self-doped Fe2O3/TiO2 ultra-thin nanoflakes an attractive candidate for photo-activation of peroxymonosulfate (HSO5-) for the degradation of naphthalene (NAP). The Fe2O3/TiO2 ultra-thin nanoflakes synthesized with 0.053 M of FeCl3 (TF3) exhibited high concentrations of Ti(3+ )and oxygen vacancies. TF3/ HSO5- /solar light system showed substantial increases in the degradation of NAP with kapp value of 0.1384 min(-1) compared to 0.057 min(-1) when no HSO5- was added to the system. The proposed system also showed appreciable degradation of NAP in real water samples. Based on scavenger studies, SO4 center dot-, center dot OH, h+ and O-2(center dot-) are generated in the reaction system. Importantly, the toxicity results indicated that the proposed system (TF3/HSO5- /solar light) is an efficient treatment process for detoxifying water contaminated with NAP.
查看更多>>摘要：A constructed MoS2/Bi2S3/BiVO4 ternary photocatalyst(MBB) mainly with a S-scheme heterostructure was loaded on a 3D lignosulfonate modified poly(vinyl formal) sponge to obtain a novel composite sponge(PLS-MBB) with an enhanced performance in synergistic adsorption and photo-Fenton degradation of various fluoroquinolones(FQs) in water. The synergistic adsorption and photocatalysis of PLS-MBB notably improved the applicable pH from 2.0 to 9.0 and reduced the dosage of Fe2+ to 0.014 mmol/L in Fenton reaction, which could achieve the degradation efficiency of 92.8 % for FQs within 60.0 min at pH 6.0. The photo-generated electrons by MBB and the redox transformation of Mo(IV)/Mo(VI) and Bi(III)/Bi(V) accelerated the conversion of Fe3+ to Fe2+; besides, the efficient adsorption of FQs on the sponge carrier promoted the surface degradation in solution, thereby causing an enhanced photo-Fenton reaction. This work provided a novel strategy to improve photo-Fenton reaction and accordingly fabricated a talented material for effective removal of organic contaminants in water.
查看更多>>摘要：Fabrication of broad-spectrum response photocatalysts in a controllable manner that can efficiently utilize solar light as much as possible remains a top priority target yet a challenging task. In this work, a facile approach of synchronous bottom-up growth was employed to construct UCNP/NMIL(Ti) nanohybrids via NH2-BDC (NH2- MIL-125-ligand) linkage between upconversion NaYbF4:Tm3+ nanoparticles (~13-nm) and NH2-MIL-125. The ligand sharing integration strategy generated abundant oxygen vacancies and coordinatively-unsaturated-metal sites, efficiently enhanced light absorption, energy-transfer upconversion (UC-PL), photo-induced e -/h+ generation, and their separation (CV, EIS, Photocurrent-density). Consequently, UCNP/NMIL(Ti) exhibited excellent acetaldehyde photodegradation activity, with 12.5-77.0-folds higher rate constants (k(a)) than those of state-ofthe-art photocatalysts under visible light and high humidity. Furthermore, the photocatalytic activity of UCNP/NMIL(Ti) only declined from 96.0% to 92.5% after five cycling-runs, demonstrating its remarkable photo catalytic stability. Considering these attributes, the current strategy provides an avenue to synthesize efficient UCNPs/MOF composites for widespread usage in a variety of commercial applications.
查看更多>>摘要：Strong metal support interaction between Ni and gamma-Al2O3, resulted from the excessive hydroxyl groups on the Al2O3 support, has restricted Ni utilization in the traditional Ni/Al2O3 catalyst, which hampered its commercial application. Meanwhile, the concept of surface defects in activating single-carbon chemicals of CH4 and CO2 has attracted much attention in heterogeneous catalysis. Thus, designing better Ni/Al2O3 system in generating surface defects without losing active Ni into Al2O3 support remains challenging. Herein, the development of tailored defect sites on Al2O3 through hydroxyl-exposed strategy shows dual role of stabilizing the active Ni sites and holding responsible for catalyzing CH4 dry reforming (DRM) reaction via a more efficient route, which emphasizes the superior behavior of the traditional Ni/Al2O3 catalyst. It is considered that it can be appropriately used for reactions using not only excellent DRM catalysts but also other Ni catalysts.
查看更多>>摘要：Although great interest is focused on development of semiconductor photoanodes for efficient photo electrochemical (PEC) water splitting, the pressing bottleneck to address the intrinsic charge transport for enhancement of PEC performance still remains to be resolved. Herein, hole transport layer (Fh-MXene) constructed by doping of MXene (Ti3C2) in Ferrihydrite (Fh) is loaded on BiVO4 photoanode. This novel BiVO4@Fh-MXene photoanode achieves high current density of 4.55 mA cm(-2) at 1.23 V versus reversible hydrogen electrode (vs. RHE), exhibiting excellent photostability. From electrochemical analysis and density functional theory calculations, high PEC performance is ascribed to incorporation of Fh-MXene as hole transport layer, enhancing conductivity and water oxidation reaction. Notably, MXene can improve band alignment of BiVO4/Fh-MXene interface by tuning work function, which strengthens the built-in electric field for more efficient hole extraction. This work provides a simple method to design photoanodes with efficient charge transport layers for feasible PEC water splitting application.
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.
NSTL
Elsevier