Search

Based on various experimental results, M3+O(–Mn4+)2 clusters in (Fe, Co, Ni)-doped MnOx catalysts were identified as the principal active sites for the aerobic oxidation of 5-hydroxymethylfurfural due to their special properties that make oxygen ‘easy come, easy go’.

Pt nanoparticles supported on three-dimensionally ordered macroporous carbon (Pt/3DC) were prepared and applied as catalyst after chirally modified with cinchonidine for the enantioselective hydrogenation of ethyl pyruvate. The catalyst was characterized by SEM, TEM, powder XRD, N 2 sorption, and CO chemisorption, which confirmed the well-defined periodic macroporous structure of Pt/3DC and the high dispersion of Pt nanoparticles on the support. High catalytic performance was achieved over chirally modified Pt/3DC catalyst in the asymmetric hydrogenation of ethyl pyruvate. A high turnover frequency of 11,800 h −1 with an enantiomeric excess of 79.5% was acquired in acetic acid. In particular, this catalyst exhibited high durability in the asymmetric hydrogenation system and could be easily reused at least 13 times with well-maintained catalytic activity and slightly decreased enantioselectivity. Moreover, the comparison of catalytic performance between Pt/3DC and commercial Pt/C as well as Pt/Al 2 O 3 was carried out.

With the rapid development of detection technologies, compatible stealth in the infrared and radar ranges has become increasingly essential not only for military application but also for personal privacy protection. In this study, we design a metamaterial window that possesses stealth ability in both the thermal infrared and broadband microwave ranges, using a particle swarm optimization algorithm to realize multi-band optimization. We experimentally verify that the proposed structure can achieve over 90% microwave absorption in the range 5.1 to 19.2 GHz (covering the X and Ku bands), with low infrared emissivity (∼0.15), and also maintain visible transmittance above 60%. Moreover, the window retains good performance up to 200 °C owing to the intrinsic properties of the material. Our multi-band optimization method enables the application of the transparent metamaterial windows in electromagnetic shielding and stealth and can potentially be applied in smart window related industries.

The novel visible-light-driven 3DOM-SrTiO3/Ag/Ag3PO4 ternary composites were fabricated and used as photocatalysts in the degradation of organic contaminants, including RhB, phenol, and MB. Through the XRD, SEM, TEM, DR UV–vis, XPS, PL spectroscopy, N2 sorption, and photoelectrochemical measurement, the obtained 3DOM-SrTiO3/Ag/Ag3PO4 ternary composites were well characterized. The effects of SrTiO3:Ag3PO4 molar ratio and stop-bands of 3DOM-SrTiO3 on the catalytic performance were systemically investigated. 3DOM-SrTiO3/Ag/Ag3PO4 ternary composite photocatalysts exhibited notably enhanced activity compared with single 3DOM-SrTiO3 and Ag3PO4 catalyst. Among these ternary photocatalysts, S35A65(300) exhibited the most excellent photocatalytic performance under visible light irradiation, which could be mainly attributed to synergy effect of the notably improved separate efficiency of photogenerated electron-hole pairs and the suitable stop-bands of 3DOM-SrTiO3(300) material. Although the gradually reduced activity in cycling tests was obtained over S35A65(300) under visible light irradiation, an excellent durability could be achieved for S35A65(300) under UV–vis light irradiation. No obvious loss in photocatalytic efficiency was observed after six cycles for RhB degradation. The notably improved enhanced durability of 3DOM-SrTiO3/Ag/Ag3PO4 ternary composites under UV–vis light irradiation could be mainly attributed to the Z-scheme mechanism of this ternary composite photocatalyst.

Three-dimensionally ordered macroporous SrTiO 3 (3DOM-SrTiO 3 ) materials with different pore sizes were originally prepared and employed as photocatalysts in the water splitting for hydrogen generation. These 3DOM-SrTiO 3 photocatalysts were characterized by XRD, SEM, TEM, EDS, DR UV–vis and N 2 sorption. Because of the slow photon effect of 3DOM-SrTiO 3 , notably enhanced efficiency of water splitting for hydrogen evolution was obtained compared with the solid-state SrTiO 3 (SS-SrTiO 3 ) and disordered porous SrTiO 3 (Disorder-SrTiO 3 ). The effect of stop-band on the efficiency of photocatalytic hydrogen production was studied by tuning the pore diameter of 3DOM-SrTiO 3 . It was found that higher hydrogen evolution efficiency could be achieved when the photonic stop-band of 3DOM-SrTiO 3 was overlapped with its band gap, which was further confirmed by the control experiments under certain wavelength light irradiation. 3DOM-SrTiO 3 (270 nm) exhibited the highest photocatalytic hydrogen evolution rate (up to 3599 μmol/g·h), which was 31 times as high as that of SS-SrTiO 3 and 11 times higher than that of Disorder-SrTiO 3 . Furthermore, these 3DOM-SrTiO 3 catalysts were very stable and no obvious loss in photocatalytic efficiency of hydrogen production was observed after five cycles.

The three-dimensionally ordered macroporous alumina-carbon composite materials were firstly prepared through a surfactant-assisted colloidal crystal template method and applied to support Pt nanoparticles. The results of SEM, XRD, TEM and N2 sorption revealed that these composite materials possessed highly ordered macroporous structures with meso- and micropores within the skeletons of macropores and that the Pt nanoparticles were well dispersed on these materials with a very narrow size distribution. These prepared Pt nanocatalysts were evaluated in the asymmetric hydrogenation of ethyl pyruvate after chiral modification with cinchonidine. Excellent catalytic activity and enantioselectivity were achieved. More importantly, these catalysts exhibited extraordinary stability and reusability during the reaction and could be reused at least 26 times without obvious loss in catalytic activity and enantioselectivity.

Quantum dots (QDs) are promising materials used for room temperature mid-infrared (MIR) photodetector due to their solution processing, compatibility with silicon and tunability of band structure. Up to now, HgTe QDs is the most widely studied material for MIR detection. However, photodetectors assembled with HgTe QDs usually work under cryogenic cooling to improve photoelectric performance, greatly limiting their application at room temperature. Here, less-toxic SnTe QDs were controllably synthesized with high crystallinity and uniformity. Through proper ligand exchange and annealing treatment, the photoconductive device assembled with SnTe QDs demonstrated ultralow dark current and broadband photo-electric response from visible light to 2 μm at room temperature. In addition, the visible and near infrared photo-electric performance of the SnTe QDs device were well maintained even standing 15 d in air. This excellent performance was due to the effective protection of the ligand on surface of the QDs and the effective transport of photo-carriers between the SnTe interparticles. It would provide a new idea for environmentally friendly mid-IR photodetectors working at room temperature.

An environmentally benign and homogeneous base-free route for 5-hydroxymethyl-2-furfural (HMF) aerobic oxidation to 2,5-furandicarboxylic acid (FDCA) in water was reported using Mg–Al–CO3 hydrotalcite-supported Pd nanoparticles (xPd/HT-n) as catalyst. The influences of the Mg/Al molar ratio of hydrotalcite and Pd loading amount on the catalytic performance of these catalysts were originally systematically investigated. These catalysts exhibited excellent catalytic activity and FDCA selectivity in the HMF oxidation, especially for 2%Pd/HT-5 and 2%Pd/HT-6; >99.9% FDCA yields were achieved for 8 h under ambient pressure and homogeneous base-free conditions. The remarkably improved catalytic performance could be attributed to the suitable basicity of the Mg–Al–CO3 hydrotalcite and the abundant OH– groups on the surface of hydrotalcite. The plausible reaction mechanism was proposed based on the results of a series of controlled experiments. Furthermore, these catalysts were quite stable and could be reused at ...

We thank Prof. J.-Q. Yu for a useful discussion. This work was supported by Tianjin Municipal Natural Science Foundation (Grant 17JCYBJC22600), China Scholarship Council (Grants 201606200096 and 201606200087), and the Fundamental Research Funds for the Central Universities. Computational support was provided by the Beijing Computing Center (BCC). Investigation of Bi-doping effects on the catalytic performance of Pt/3DOM-Ce1−xBixO2−δ in the aerobic oxidation of 5-hydroxymethyl-2-furfural allows us to reveal the promoted catalytically active sites: the asymmetrical oxygen vacancies coordinated with one Bi and up to three Ce cations, such as Bi-□(-Ce)3, where □ represents an oxygen vacancy, which can easily gain oxygen atoms in favor of the CeO2 structure, and, when filled with oxygen, easily release oxygen anions in favor of six-coordination for Bi3+. The loss of electrons in the reduction of oxygen atoms at these sites would be replenished by electron transfer from Pt nanoparticles eventually promoting the oxidation potential of the Pt nanoparticles. The present work points out that the promoted catalytic properties in Bi-doped CeO2 are mainly due to the asymmetric structures of the oxygen vacancies, rather than simply to the number of oxygen vacancies. The newly proposed model of asymmetrical active sites and electron transfer mechanism may shed light on the physicochemical properties of other solid solution substrate-supported metal nanoparticle catalysts. Postprint

This work was supported by the National High Technology Research and Development Program of China (Grant No. 2012AA063008), the Tianjin Municipal Natural Science Foundation (Grant Nos. 17JCYBJC22600 and 15JCTPJC63500), China Scholarship Council (Grant 201606200096), and the Fundamental Research Funds for the Central Universities. New ternary composites based on three dimensionally ordered macroporous (3DOM) SrTiO3 (CdS/Au/3DOM-SrTiO3) were prepared and used as photocatalysts in visible light (λ > 420 nm) photocatalytic water splitting for hydrogen evolution. Through optimizing the pore size of 3DOM-SrTiO3 materials and the loading amounts of Au and CdS, CdS/Au/3DOM-SrTiO3(300), templated by 300 nm sized poly(methyl methacrylate) colloids, was found to exhibit a remarkably enhanced photocatalytic hydrogen evolution rate (2.74 mmol/h•g), which was 3.2 times as high as that of CdS/Au/C-SrTiO3 catalyst based on commercial SrTiO3. This notably enhanced photocatalytic performance was mainly attributed to the slow photon enhancement effect of 3DOM-SrTiO3(300) material, which significantly promoted the light harvesting efficiency of ternary composite for the slow photon region of 3DOM-SrTiO3(300) was well matched with the optical absorption band of photocatalyst. Further depositing Pt nanoparticles on CdS/Au/3DOM-SrTiO3(300) composite as a co-catalyst, an extraordinarily high hydrogen evolution rate (up to 5.46 mmol/g•h) and apparent quantum efficiency (42.2% at 420 nm) were achieved because of the synergistic effect of efficient carrier separation, Au SPR effect, and slow photon effect. Furthermore, these ternary CdS/Au/3DOM-SrTiO3 composite photocatalysts were very stable and could be easily recycled four times in visible light photocatalytic water splitting experiments without any loss in activity. Postprint