Tetraphenylporphyrin-based Chelating Ligand Additive as a Molecular Sieving Interfacial Barrier toward Durable Aqueous Zinc Metal Batteries.

The sustained water consumption and uncontrollable dendrite growth strongly hamper the practical applications of rechargeable zinc (Zn) metal batteries (ZMBs). Herein, for the first time, we demonstrate that trace amount of chelate ligand additive can serve as a "molecular sieve-like" interfacial barrier and achieve highly efficient Zn plating/stripping. As verified by theoretical modeling and experimental investigations, the benzenesulfonic acid groups on the additive molecular not only facilitates its water solubility and selective adsorption on the Zn anode, but also effectively accelerates the de-solvation kinetics of Zn2+ . Meanwhile, the central porphyrin ring on the chelate ligand effectively expels free water molecules from Zn2+ via chemical binding against hydrogen evolution, and reversibly releases the captured Zn2+ to endow a dendrite-free Zn deposition. By virtue of this non-consumable additive, high average Zn plating/stripping efficiency of 99.7 % over 2100 cycles together with extended lifespan and suppressed water decomposition in the Zn||MnO2 full battery were achieved, thus opening a new avenue for developing highly durable ZMBs.

Progress on metal-support interactions in Pd-based catalysts for automobile emission control.

The interactions between metals and oxide supports, so-called metal-support interactions (MSI), are of great importance in heterogeneous catalysis. Pd-based automotive exhaust control catalysts, especially Pd-based three-way catalysts (TWCs), have received considerable research attention owing to its prominent oxidation activity of HCs/CO, as well as excellent thermal stability. For Pd-based TWCs, the dispersion, chemical state and thermal stability of Pd species, which are crucial to the catalytic performance, are closely associated with interactions between metal nanoparticles and their supporting matrix. Progress on the research about MSI and utilization of MSI in advanced Pd-based three-way catalysts are reviewed here. Along with the development of advanced synthesis approaches and engine control technology, the study on MSI would play a notable role in further development of catalysts for automobile exhaust control.

Destructive and Protective Effects of NH3 on the Low-Temperature Hydrothermal Stability of SAPO-34 and Cu-SAPO-34.

The influences of gaseous, weakly adsorbed, and strongly adsorbed NH3 on the low-temperature (<100 °C) hydrothermal stability of SAPO-34 and Cu-SAPO-34 were investigated. NH3 temperature-programmed desorption (NH3-TPD), 1H magic angle spinning nuclear magnetic resonance (MAS NMR), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were adopted to characterize the adsorption states of NH3 and H2O in SAPO-34, and the destruction of the SAPO-34 framework was revealed by direct and cross-polarization 29Si, 27Al, and 31P MAS NMR. Gaseous NH3 coadsorbed with H2O inside SAPO-34 micropores and induced the hydrolysis of framework P-O-Al and Si-O(H)-Al bonds. Weakly adsorbed NH3 was released during aging and played a similar negative role to gaseous NH3. When being combined with hydrolyzed Al species from the framework, active Cu ions transformed to inactive CuAl2O4-like species, leading to deactivation in low-temperature SCR of Cu-SAPO-34. Strongly adsorbed NH4+ via 200 °C preadsorption protected the framework integrity of SAPO-34 and the SCR activity of Cu-SAPO-34.

Rational Design and Preparation of Pt-LDH/CeO2 Catalyst for High-Efficiency Photothermal Catalytic Oxidation of Toluene.

Volatile organic compounds (VOCs) are attracting much more attention due to their contributions to air pollution and human health problems. Photothermal catalytic oxidation is considered as an energy-saving method for the removal of VOCs. However, the efficiency of the photothermal catalytic system is still suffering from the low activity of the catalyst due to its poor response to visible light and low efficiency of charge separation. Here, few-layer CoAl-LDH (layered double hydroxide) was prepared as an advantageous support for loading Pt nanoparticles to obtain Pt-LDH, which were coated on CeO2 nanoparticles. Type II heterojunctions were formed on the interface of LDH and CeO2. In photocatalysis, the hot electrons will move to CeO2, which is better at the activation of O2 molecules, and holes will concentrate on the LDHs, which have plenty of hydroxyls to generate •OH radicals. Furthermore, the Schottky heterojunctions between LDH and Pt nanoparticles benefit the improvement of light absorption by the localized surface plasmon resonance of Pt nanoparticles. As a consequence, a high removal rate of toluene (75.7%) at a weight-hourly space velocity of 23340 mL/(g·h) under visible light irradiation (160 mW/cm2, λ > 400 nm) at room temperature was achieved over the Pt-LDH/CeO2 catalyst. The catalyst design provides a useful method to prepare high-efficiency photothermal catalysts.

A strategy to construct a highly active CoxP/SrTiO3(Al) catalyst to boost the photocatalytic overall water splitting reactions.

Hydrogen production from overall water splitting using SrTiO3(Al)-based semiconductors is one of the most promising routes to address energy and environmental concerns. Noble metals are needed to accelerate water splitting by promoting the charge transfer and providing active sites. However, noble metal-based catalysts have high prices and rare resources. Herein, we demonstrate a strategy to construct highly active CoxP/SrTiO3(Al) for overall water splitting. Hydrothermal method followed by an ultrasonic process was applied to prepare CoxP dots, which were loaded on the whole surface of SrTiO3(Al) as bifunctional cocatalysts. Interestingly, the CoxP dots on the (110) planes of SrTiO3(Al) were partially oxidized for the OER reaction. However, CoxP dots on the (100) planes of SrTiO3(Al) for HER kept it as it was. The as-prepared CoxP/SrTiO3(Al) photocatalyst shows a stable HER rate of 1.36 mmol-1 h-1 and OER rate of 0.635 mmol-1 h-1. The strong interaction between CoxP and SrTiO3(Al) not only facilitates rapid charge separation but also provides a highly active site for overall water splitting. Our study provides a valuable method for constructing noble-metal-free SrTiO3(Al)-based photocatalysts.

Quasi-operando quantification of Cu(II) ions in Cu-SSZ-13 catalyst by an NH3 temperature-programmed reduction method.

A quasi-operando NH3 temperature-programmed reduction method (NH3-TPR), with N2:Cu = 1:1, is developed to quantify total Cu(ii) ions in Cu-SSZ-13 quenched from SCR-relevant reactions, and its accuracy is confirmed by in situ EPR. [Cu(OH)]+-Z and Cu2+-2Z can be further distinguished by NH3 reduction temperatures, and their different reducibility in SCR is revealed.

Size effect of Pt nanoparticles in acid-assisted soot oxidation in the presence of NO.

Pt/Al2O3 catalysts with mean Pt particle size ranged from 2.7 to 7.1 nm were synthesized by chemical reduction method, and the sulfated counterparts were prepared by impregnation of sulfuric acid. The turnover frequency of platinum for soot oxidation under loose contact conditions in a feed flow containing NO and O2 are positively correlated with the size of platinum. The sulfated Pt/Al2O3 exhibits higher catalytic activity for soot oxidation in the presence of NO despite their reduced ability for NO2 production. Such a contradiction is more significant for those catalysts with smaller platinum particles. Herein, the catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), inductive coupled plasma (ICP) emission spectrometry, CO chemisorption, thermogravimetric analysis (TGA), NH3 temperature-programmed desorption (NH3-TPD), NO temperature-programmed oxidation (TPO) and NOx temperature-programmed desorption (TPD). Possible effect of Pt particle size for the catalytic oxidation of soot in the presence of NO was presented based primarily on the promoted NO2 transfer efficiency onto the soot pushed by the acidic catalysts.

MOF-derived (MoS2, γ-Fe2O3)/graphene Z-scheme photocatalysts with excellent activity for oxygen evolution under visible light irradiation.

Constructing Z-scheme heterojunctions is considered as an effective strategy to obtain catalysts of high efficiency in electron-hole separation in photocatalysis. Unfortunately, suitable heterojunctions are difficult to fabricate because the direct interaction between two semiconductors may lead to unpredictable negative effects such as electron scattering or electron trapping due to the existence of defects which causes the formation of new substances. Furthermore, the van der Waals contact between two semiconductors also results in bad electron diffusion. In this work, a MOF-derived carbon material as a Z-scheme photocatalyst was synthesized via one-step thermal treatment of MoS2 dots @Fe-MOF (MIL-101). Under visible light irradiation, the well-constructed Z-scheme (MoS2, γ-Fe2O3)/graphene photocatalyst shows 2-fold photocatalytic oxygen evolution activity (4400 µmol g-1 h-1) compared to that of γ-Fe2O3/graphene (2053 µmol g-1 h-1). Based on ultraviolet photoelectron spectrometry (UPS), Mott-Schottky plot, photocurrent and photoluminescence spectroscopy (PL) results, the photo-induced electrons from the conduction band of γ-Fe2O3 could transport quickly to the valence band of MoS2 via highly conductive graphene as an electron transport channel, which could significantly enhance the electron-hole separation efficiency as well as photocatalytic performance.

Deactivation of Cu-SAPO-34 by urea-related deposits at low temperatures and the regeneration.

Selective catalytic reduction (SCR) with urea catalyzed by Cu-SAPO-34 is an effective method to eliminate NOx from diesel exhaust. However, urea-related deposits may form during cold-start and urban driving due to low exhaust temperatures. The activity of Cu-SAPO-34 at 175°C is significantly degraded by urea exposure, and 300°C is required for regeneration. Through in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature-programmed hydrolysis studies, the dominant stable deposit at 175°C is identified as biuret, which can be eliminated at 300°C. The urea-derived deactivation and regeneration mechanisms of Cu-SAPO-34 were compared with those of anatase-supported catalysts.

Optimizing the crystallinity and acidity of H-SAPO-34 by fluoride for synthesizing Cu/SAPO-34 NH3-SCR catalyst.

A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media. The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature-programmed desorption of NH3 (NH3-TPD) and nuclear magnetic resonance (NMR) measurements. The results showed that a certain concentration of F(-) anions promoted the nucleation and crystallization of H-SAPO-34. The H-SAPO-34 synthesized in the fluoride media showed high crystallinity, uniform particle size distribution, large specific surface area and pore volume, and enhanced acidity. Therefore, Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH3 (NH3-SCR) reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species.

Effect of water vapor on NH3-NO/NO2 SCR performance of fresh and aged MnOx-NbOx-CeO2 catalysts.

A MnOx-NbOx-CeO2 catalyst for low temperature selective catalytic reduction (SCR) of NOx with NH3 was prepared by a sol-gel method, and characterized by NH3-NO/NO2 SCR catalytic activity, NO/NH3 oxidation activity, NOx/NH3 TPD, XRD, BET, H2-TPR and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The results indicate that the MnOx-NbOx-CeO2 catalyst shows excellent low temperature NH3-SCR activity in the temperature range of 150-300°C. Water vapor inhibits the low temperature activity of the catalyst in standard SCR due to the inhibition of NOx adsorption. As the NO2 content increases in the feed, water vapor does not affect the activity in NO2 SCR. Meanwhile, water vapor significantly enhances the N2 selectivity of the fresh and the aged catalysts due to its inhibition of the decomposition of NH4NO3 into N2O.

DRIFT study of CuO-CeO2-TiO2 mixed oxides for NOx reduction with NH3 at low temperatures.

A CuO-CeO2-TiO2 catalyst for selective catalytic reduction of NOx with NH3 (NH3-SCR) at low temperatures was prepared by a sol-gel method and characterized by X-ray diffraction, Brunner-Emmett-Teller surface area, ultraviolet-visible spectroscopy, H2 temperature-programmed reduction, scanning electron microscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). The CuO-CeO2-TiO2 ternary oxide catalyst shows excellent NH3-SCR activity in a low-temperature range of 150-250 °C. Lewis acid sites generated from Cu(2+) are the main active sites for ammonia activation at low temperature, which is crucial for low temperature NH3-SCR activity. The introduction of ceria results in increased reducibility of CuO species and strong interactions between CuO particles with the matrix. The interactions between copper, cerium and titanium oxides lead to high dispersion of metal oxides with increased active oxygen and enhanced catalyst acidity. Homogeneously mixed metal oxides facilitate the "fast SCR" reaction among Cu(2+)-NO, nitrate (coordinated on cerium sites) and ammonia (on titanium sites) on the CuO-CeO2-TiO2 catalyst at low temperatures.

Facile synthesis of hierarchical porous γ-Al2O3 hollow microspheres for water treatment.

Hierarchical porous γ-Al2O3 hollow microspheres were synthesized by a modified spray drying method. Ageing the precipitated precursor and spray-drying assisted by NH4Cl salts are considered as two key steps for the synthesis of γ-Al2O3 hollow microspheres. The mechanism of the formation of hierarchical porous γ-Al2O3 hollow microsphere was proposed involving phase transformation from aluminum hydroxide to laminar boehmite during ageing and a following self-assembling process with NH4Cl as the template during spray drying. The meso-/macro-pores in γ-Al2O3 mainly arise from the stacking of the laminar boehmites which are obtained by ageing the precipitated precursors at 90°C. NH4Cl, which was the byproduct from the reaction between AlCl3·6H2O and NH3·H2O, was demonstrated to be an excellent template to act as the core and the barrier for separation of laminar boehmites. No extra NH4Cl was added. The as-synthesized hierarchical porous γ-Al2O3 hollow microsphere presented remarkably higher adsorption capacity, which is thirty times higher adsorption rate for Congo Red than the solid microsphere containing only small mesopores.

Total oxidation of propane on Pt/WOx/Al2O3 catalysts by formation of metastable Ptδ+ species interacted with WOx clusters.

A series of Pt/Al(2)O(3) catalysts with various tungsten oxide loadings were prepared by a stepwise wet impregnation method. The catalysts were characterized by X-ray diffraction, nitrogen physisorption, Raman, UV-vis diffuse reflectance, transmission electron microscopy and infrared spectroscopy of adsorbed probe molecules (CO, NH(3) or C(3)H(8)). The propane oxidation activity of Pt/Al(2)O(3) catalyst is significantly improved by the addition of tungsten oxide. The tungsten oxide overlayer is presented as monomeric/polymeric WO(x) clusters and WO(3) crystals depending on the loading amount. The most active catalyst occurs at an intermediate surface tungsten density corresponding to the maximum of polytungstate species. The electronic interactions between Pt and WO(x) clusters lead to the generation of more reducible Pt(δ+) species which are suggested to be active sites for propane oxidation. Basically, a simple model is proposed involving the initial CH bond activation at the platinum-tungsten oxide interface.

Effects of WO(x) modification on the activity, adsorption and redox properties of CeO2 catalyst for NO(x) reduction with ammonia.

A series of WO3/CeO2 (WO(x)/CeO2) catalysts were synthesized by wet impregnation of ammonium metatungstate on a CeO2 support. The resulting solid acid catalysts were characterized by X-ray diffraction (XRD), UV-Vis spectroscopy (UV-Vis), Raman spectroscopy (Raman), in-situ Fourier transform infrared spectroscopy (in-situ FT-IR) of ammonia adsorption, NH3-TPD, H2 temperature-programmed reduction (H2-TPR), NH3/NO oxidation and activity measurements for NO(x) reduction by NH3 (NH3-SCR). The results show that polytungstate (WO(x)) species are the main species of tungsten oxide on the surface of ceria. The addition of tungsten oxide enhances the Brönsted acidity of ceria catalysts remarkably and decreases the amount of surface oxygen on ceria, with strong interaction between CeO2 and WO(x). As a result, the N2 selectivity of NH3 oxidation and NH3-SCR at high temperatures (> 300 degrees C) is enhanced. Therefore, a wide working temperature window in which NO(x) conversion exceeds 80% (NO(x) conversion > 80%) from 200 to 450 degrees C, is achieved over 10 wt.% WO(x)/CeO2 catalyst. A tentative model of the NH3-SCR reaction route on WO(x)/CeO2 catalysts is presented.

Modification of CeO2-ZrO2 catalyst by potassium for NOx-assisted soot oxidation.

Potassium-modified ceria-zirconia catalyst was synthesized by wetness impregnation method. The ageing treatment was performed in static air at 800degrees C for 20 hr to evaluate the thermal stability of the catalyst. The catalysts were characterized by X-ray diffraction, BET surface area, oxygen storage capacity, NO(x)-temperature programmed desorption and soot-temperature programmed oxidation measurements. By introduction of potassium, the maximum soot oxidation rate temperature (T(m)) of the ceria-zirconia based catalyst decreased from 525 to 428 degrees C in the presence of NO under a loose contact mode. The shift of T(m) of the K-modified catalyst after ageing is only 15 degrees C. The enhanced activity of the aged catalyst mainly lies in the promotional effect of potassium on the NO(x)/oxygen storage capacity as well as the soot-catalyst contact.

Photoinduced hydroxyl radical and photocatalytic activity of samarium-doped TiO(2) nanocrystalline.

Sm(3+)-doped TiO(2) nanocrystalline has been prepared by sol-gel auto-combustion technique and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and also UV-vis diffuse reflectance spectroscopy (DRS). These Sm(3+)-doped TiO(2) samples were tested for methylene blue (MB) decomposition and *OH radical formation. The analysis of *OH radical formation on the sample surface under UV irradiation was performed by fluorescence technique with using terephthalic acid, which readily reacted with *OH radical to produce highly fluorescent product, 2-hydroxyterephthalic acid. It was observed that the presence of Sm(3+) ion as a dopant significantly enhanced the photocatalytic activity for MB degradation under UV light irradiation because both the larger specific surface area and the greater the formation rate of *OH radical were simultaneously obtained for Sm(3+)-doped TiO(2) nanocrystalline. The adsorption experimental demonstrated that Sm(3+)-TiO(2) had a higher MB adsorption capacity than undoped TiO(2) and the adsorption capacity of MB increased with the increase of samarium ion content. The results also indicated that the greater the formation rate of *OH radical was, the higher photocatalytic activity was achieved. In this study, the optimum amount of Sm(3+) doping was 0.5 mol%, at which the recombination of photo-induced electrons and holes could be effectively inhibited, the highest formation rate of *OH radicals was, and thereby the highest photocatalytic activity was achieved.