Lee, JuyeonBack, SeoinJang, HongjeSa, Young Jin...
8页
查看更多>>摘要：An efficient approach to shift the reaction pathway from the 4-electron oxygen reduction reaction (4e(-) ORR) to the 2e(-) ORR is by fabricating precious metal compounds. The selectivity of the latter reaction is critical for the efficiency of H2O2 electrosynthesis technology. Herein, we demonstrate the high 2e(-) ORR activity and selectivity of a nanocoral-shaped Pd-based compound comprising Pd17Se15 and Pd3B mixed phases (Pd-Se-B NC). In contrast, metallic Pd exhibited nearly 100% 4e- ORR selectivity. The mass activity of Pd-Se-B NC for H2O2 generation was similar to 37-fold higher than that of the Pd black catalyst. Importantly, Pd-Se-B NC exhibited one of the highest H2O2 electrosynthesis activities in neutral media reported to date. The chemical states and composition of the Pd-Se-B NC remained almost intact even after sustained electrocatalysis.
查看更多>>摘要：Direct photocatalytic water splitting is an attractive strategy for clean energy, in which, organic photocatalytic systems with broad light-harvesting region and efficient charge separation are highly desired and still challenging. In this paper, three multi-branched organic dyes were designed and synthesized with dipolar, V-shaped, and octupolar geometries, respectively. The multiple intramolecular charge transfer processes by electronic pull-push effect along the branches can provide more channels for light-harvesting and carrier transporting. Also, the interactions with polymeric carbon nitride (PCN) can be optimized by multiple anchoring units and defect filling effect, resulting in the gradually enhanced photocatalytic hydrogen evolution performance with the increased number of branches. Accordingly, the highest one of 996.9 mu mol h(-1) was achieved, which is over 40-folders that of PCN/Pt (24.8 mu mol h(-1)) under the same conditions. It provides an efficient strategy for molecular design of organic dyes as photocatalyst, promoting development of PHE system from the molecular level.
查看更多>>摘要：Urea perylene imide polymer (UPDI) is successfully recombined with Co(NO3)(2) molecules into one-dimensional nanocrystals (Co-UPDI) for enhanced photocatalytic oxygen evolution (POE) under visible light. Co-UPDI as photocatalyst exhibits more an order of magnitude of POE rate than UPDI at pH = 4.8 (8.00 vs. 0.58 mmol h(-1)g(-1)), which is the highest among reported POE tests in aqueous colloid system with AgNO3 as sacrificial agent. The apparent quantum yield (AQY) reaches 4.39 % at 450 nm. The systematical experiments reveals that the heterojunction formation between UPDI line and Co(NO3)(2) molecules is crucial through the coordination of Co with N atoms. Consequently, the rigidity of UPDI line enhances, H-type stacking of PDI moiety becomes closer, and CoOOH as cocatalyst in-situ forms during POE. Meanwhile, more excitons with longer lifetime generate and more quickly transfer in Co-UPDI than UPDI nanocrystals. This work provides an efficient strategy for photocatalytic water oxidation.
查看更多>>摘要：Transformation of ethanol to more valuable C4+ alcohols by coupling reaction has been of great interest from the point of view of chemistry and technology of biomass utilization. This work reports atomic Ru on Mg and Al containing layered double oxides (MgAl-LDO) for ethanol coupling to C4+ alcohols. The atomic Ru remarkably promotes the coupling of ethanol, achieving a selectivity of 82.6% to C4+ alcohols under an ethanol conversion of 29.6%. Through tailoring Ru dispersion and acid-base properties, it has been found that atomic Ru promotes ethanol dehydrogenation and the following aldol condensation of acetaldehyde.
查看更多>>摘要：Catalytic fast pyrolysis of polyolefinic waste streams was investigated to recover valuable base chemicals at high selectivity. HZSM-5 zeolite with different properties, affected by Si/Al, mesoporosity, phosphorus stabilization, and steaming, were tested and thoroughly characterized. Different feeds, catalyst/feed ratios and reaction temperatures were evaluated in a micropyrolysis reactor coupled to two-dimensional gas chromatography. While unmodified HZSM-5 rapidly deactivated, phosphorus-modified and steamtreated HZSM-5 showed almost no deactivation due to its lower coking propensity during 130 runs with stable conversion towards C5+ aliphatics and high C-2-C-4 olefins selectivity (-75%) using post-consumer mixed polyolefins. The performance of this direct olefins production route with unprecedented high olefin selectivity was further evaluated in a plantwide context. It was found that it requires-37% lower energy input than the plastics pyrolysis followed by pyrolytic oil steam cracking, while it results to at least a one order of magnitude lower environmental burden as compared to waste incineration.
查看更多>>摘要：A novel heterogeneous and porous FeSe2_x @C-5 with abundant Se vacancies (V-se) was facilely synthesized via one-step carbonization-selenization approach from Fe-MOFs (metal-organic frameworks) and firstly applied in activating peroxymonosulfate (PMS) for iohexol (IOH) removal, exhibiting extraordinary catalytic performance with superior stability and adaptability. The roles and functions of V-se in the reaction system are deeply elucidated. Strikingly, systematic characterization and theoretical calculations revealed that V-se can modulate the surface electronic structure and accelerate Fe3+/Fe2+ cycle, leading to the strengthened binding energy and accelerated charge deliver for PMS activation. Accordingly, Iohexol (15 mg/L) can be eliminated within 30 min in FeSe2_x @C-5/PMS system, with apparent reaction rate constant (k(app)) 23.7 times higher than that in FeSe2/ PMS system. This study not only contributes to a tutorial guideline for designing high-performance catalysts by virtue of structural control and V-se engineering, but also extends its potential application in low-strength wastewater treatment.
Bi, QingyuanSong, ErhongChen, JiachengRiaz, Muhammad Sohail...
11页
查看更多>>摘要：A nanocomposite design is proven for achieving efficient, selective, and robust alkyne semi-hydrogenation through photocatalytic process, which avoids the use of additional heat sources and traditional toxic Pb additives. The gold nanoparticles (Au NPs) coupled crystalline-core@amorphous-shell structured and wide-spectrum responsive black titania (BT) with enhanced surface plasma properties holds the key to attaining high activity and selectivity. The hot electron injection from conductive BT to the surface of plasmonic Au NPs stimulated by solar light activates the alkynes and directly participates in the selective conversion to overcome the energy barriers. The engineered Au/BT gives a record turnover frequency of 1012 h(-1) and excellent stability for phenylacetylene semi-hydrogenation under solar light irradiation and shows broad scope toward selective hydrogenation of alkynes containing various substituent groups of -CH3, -OH, and -Cl. The kinetic isotope effects and in situ infrared spectroscopy analysis for structure-activity relationship and reaction mechanism of phenyl acetylene reduction were also demonstrated.
查看更多>>摘要：Gas adsorption/desorption process and conversion efficiency of solar energy are crucial to photocatalytic CO2 conversion. Here, we report the synthesis of a metal-organic-framework based monolithic NF@ZnO/Au@ZIF-8 photocatalyst that can simulate the respiratory process to accelerate adsorption of CO2 and desorption of CH4 during the photocatalytic reaction. Particularly, this selective-breathing monolithic photocatalyst could coupling external magnetic field into the photocatalytic process, achieving photo-thermal-magnetic field synergy in the reaction system. Upon this photo-thermal-magnetic coupling, the temperature of surface reaction could be elevated to about 180 degrees C, leading to a drastically improved charge transfer behavior and the significantly increased breathing efficiency. The yield of CH4 over the selective-breathing monolithic NF@ZnO/Au@ZIF-8 photocatalyst reaches 270.02 mu mol/g with a high stability and a high selectivity up to 89.72%. This study provides an ideal approach for the design of monolithic catalysts not only with balanced gas adsorption desorption property, but also endowed with multi-field coupling ability.
查看更多>>摘要：Highly efficient platinum-group-metal (PGM) free catalysts for alkaline hydrogen oxidation reaction (HOR) are of vital issues for the development of alkaline hydroxide exchange membrane fuel cells (HEMFCs). Herein, with the help of interface engineering by the in-situ electrochemical surface reconfiguration strategy, the seamless nickel nitrides-nickel hydr(oxy)oxide (denoted as Ni3N-Ni(OH)(2)) heterostructures were developed. From the systematic electrochemical measurements, the impressive HOR performance such as nearly zero onset over-potential, larger exchange current density, excellent long-term durability, and robust CO tolerance in alkaline media, are obtained by the optimized Ni3N-Ni(OH)(2) catalyst, thus rendering it significant potential for applications in HEMFCs. Furthermore, this catalyst also exhibits superior HER activity, approaching to that of Pt/C catalyst. The tailored d band center of Ni and the enhanced hydroxyl adsorption ability at Ni3N-Ni(OH)(2) heterojunctions are evidenced by the comprehensive spectroscopy and electrochemical analyses, which are favor-able for the accelerated Volmer step toward alkaline hydrogen electrocatalysis.
查看更多>>摘要：Mn2O3 is an exceptional earth-abundant mineral that has been extensively applied in catalytic oxidation because of the strong redox couples like Mn3+/Mn2+ and Mn4+/Mn3+ exposed on Mn2O3 surface. Herein, the catalytic activity of Mn2O3 in photothermal degradation of toluene was regulated by halogens including F-, Cl-, and Br-. As the electronegativity ordered in F (3.98) > O (3.44) > Cl (3.16) > Br (2.96), F- doped Mn2O3 overperforms Cl- doped and Br- doped Mn2O3 in decomposing toluene. DFT theoretical calculation illustrates that F- attracts the shared electrons from Mn to itself, the deviated charge center stretches the adjacent Mn-O bonds and boosts the generation of abundant oxygen vacancies, helping to strengthen the catalytic activity of Mn2O3. Conversely, MnO bonds are shortened by Cl- and Br- that have lower electronegativity than O. The multiple electrons circling Cl- and Br- push Mn towards O and squeeze Mn-O bonds, resulting in the formation of passivated Mn2O3. In conjunction with Mn redox couples and oxygen vacancies, 99% of 400 ppm toluene can be eliminated by F doped Mn2O3, corresponding mineralization rate is high up to 95.8%.
NSTL
Elsevier