Co-reporter:Yanqun Tang, Ruirui Wang, Ye Yang, Dongpeng Yan, and Xu Xiang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 30) pp:19446
Publication Date(Web):July 15, 2016
DOI:10.1021/acsami.6b04937
The water oxidation half-reaction is considered to be a bottleneck for achieving highly efficient solar-driven water splitting due to its multiproton-coupled four-electron process and sluggish kinetics. Herein, a triadic photoanode consisting of dual-sized CdTe quantum dots (QDs), Co-based layered double hydroxide (LDH) nanosheets, and BiVO4 particles, that is, QD@LDH@BiVO4, was designed. Two sets of consecutive Type-II band alignments were constructed to improve photogenerated electron–hole separation in the triadic structure. The efficient charge separation resulted in a 2-fold enhancement of the photocurrent of the QD@LDH@BiVO4 photoanode. A significantly enhanced oxidation efficiency reaching above 90% in the low bias region (i.e., E < 0.8 V vs RHE) could be critical in determining the overall performance of a complete photoelectrochemical cell. The faradaic efficiency for water oxidation was almost 90%. The conduction band energy of QDs is ∼1.0 V more negative than that of LDH, favorable for the electron injection to LDH and enabling a more efficient hole separation. The enhanced photon-to-current conversion efficiency and improved water oxidation efficiency of the triadic structure may result from the non-negligible contribution of hot electrons or holes generated in QDs. Such a band-matching and multidimensional triadic architecture could be a promising strategy for achieving high-efficiency photoanodes by sufficiently utilizing and maximizing the functionalities of QDs.Keywords: layered double hydroxides; photoanodes; photoelectrochemistry; quantum dots; water oxidation
Co-reporter:Wanhong He, Ruirui Wang, Lu Zhang, Jie Zhu, Xu Xiang and Feng Li
Journal of Materials Chemistry A 2015 vol. 3(Issue 35) pp:17977-17982
Publication Date(Web):05 Aug 2015
DOI:10.1039/C5TA04105H
A BiVO4 photoanode was modified with a multi-functional layered double hydroxide (LDH) nanowall overlayer for PEC water oxidation. The composite photoanode exhibits a tremendous cathodic shift of the onset potential (∼540 mV) and more than 2-fold enhancement in the oxidation efficiency and IPCE value.
Co-reporter:Wanhong He, Ruirui Wang, Chen Zhou, Junjiao Yang, Feng Li, and Xu Xiang
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 43) pp:10723-10730
Publication Date(Web):October 14, 2015
DOI:10.1021/acs.iecr.5b02460
A facile and green method was developed to control the structure of the prevailing BiVO4 photoanodes derived from electrodeposited Bi precursors, in which Zn2+ ions were added as a directing agent to tune the deposition of Bi particles. The particle size and density of the Bi precursors were affected by the amount (or concentration) of Zn2+ ions added. The structural evolution of BiVO4 was consistent with that of the Bi precursor particles. An optimal concentration of Zn2+ ions resulted in smaller particle sizes and produced appropriate interparticle spacing of BiVO4 photoanodes, which possessed enhanced photocurrent and improved charge separation efficiency. The enhancement is mostly ascribed to the suppression of carrier recombination in the bulk. This work demonstrates an effective way to adjust the structure and the subsequent photoelectrochemical performance of BiVO4 photoanodes by a cation-tuned Bi precursor strategy without the use of hard templates or complex directing agents.
Co-reporter:Yanfei Wang;Xiang Zhang;Haodong Wei;Bing Zhang;Rongfeng Chen
Polymer Composites 2015 Volume 36( Issue 2) pp:229-236
Publication Date(Web):
DOI:10.1002/pc.22934
A novel poly(acrylic acid-co-acrylamide)/halloysite nanotubes [PAA-AM/HNTs] superabsorbent composite was synthesized by free radical polymerization with using HNTs as an inorganic additive. The composite was characterized by Fourier transform infrared spectroscopy, scanning electron microscope, and thermogravimetric analysis. The results revealed that HNTs and PAA-AM were combined well together to form a porous structure with a pore size of about 10 μm, and HNTs were uniformly distributed in the composite. The thermal stability was improved by adding HNTs in the composite. The influences of contents of initiator and halloysite, neutralization degree of AA, and molar ratio of AM to AA on water absorbency were investigated. The water absorbency and the water retention capacity were improved after adding HNTs into PAA-AM. The composite containing 10% HNTs had the highest water absorbency of 1276 g/g in distilled water. Moreover, PAA-AM/HNTs composite also had a high swelling rate within 60 min and could maintain 78% initial swelling capability after five reswelled test. The substantial enhancement of swelling properties enables PAA-AM/HNTs suitable for numerous practical applications. POLYM. COMPOS., 36:229–236, 2015. © 2014 Society of Plastics Engineers
Co-reporter:Wanhong He;Dr. Ye Yang;Liren Wang;Junjiao Yang; Xu Xiang; Dongpeng Yan; Feng Li
ChemSusChem 2015 Volume 8( Issue 9) pp:1568-1576
Publication Date(Web):
DOI:10.1002/cssc.201403294
Abstract
The development of earth-abundant semiconductor photoelectrodes is of great importance to high-efficiency and sustainable photoelectrochemical water splitting. Herein, a one-dimensional TiO2 array photoanode was sheathed with an ultrathin overlayer of phosphated nickel–chromium double-metal hydroxide by a photoassisted modification and deposition strategy. The core/shell array photoanode resulted in a large cathodic shift of photocurrent onset potential (≈200 mV). Nearly 100 % oxidative efficiency for PEC water oxidation was achieved over a wide range of potential. Mechanism studies show that the modification of phosphate leads to significantly improved charge separation. The amorphous hydroxide sheath could efficiently inhibit oxygen reduction reactions. Therefore, this strategy enables the simultaneous suppression of surface carrier recombination and back reactions, which is promising to improve the water oxidation efficiency of currently prevailing photoanodes.
Co-reporter:Wanhong He;Dr. Ye Yang;Liren Wang;Junjiao Yang; Xu Xiang; Dongpeng Yan; Feng Li
ChemSusChem 2015 Volume 8( Issue 9) pp:
Publication Date(Web):
DOI:10.1002/cssc.201500418
Co-reporter:Yanyan Wang;Wanhong He;Liren Wang;Junjiao Yang;Dr. Xu Xiang;Dr. Bing Zhang;Dr. Feng Li
Chemistry – An Asian Journal 2015 Volume 10( Issue 7) pp:1561-1570
Publication Date(Web):
DOI:10.1002/asia.201500188
Abstract
The hydrogenation of α,β-unsaturated aldehydes to allylic alcohols or saturated aldehydes provides a typical example to study the catalytic effect on structure-sensitive reactions. In this work, supported platinum nanocatalysts over hydrotalcite were synthesized by an alcohol reduction method. The Pt catalyst prepared by the reduction with a polyol (ethylene glycol) outperforms those prepared with ethanol and methanol in the hydrogenation of cinnamaldehyde. The selectivity towards the C=O bond is the highest over the former, although its mean size of Pt particles is the smallest. The hydroxyl groups on hydrotalcite could act as an internally accessible promoter to enhance the selectivity towards the C=O bond. The optimal Pt catalyst showed a high activity with an initial turnover frequency (TOF) of 2.314 s−1. This work unveils the synergic effect of metal valence and in situ promoter on the chemoselective hydrogenation, which could open up a new direction in designing hydrogenation catalysts.
Co-reporter:Yanyan Wang;Wanhong He;Liren Wang;Junjiao Yang;Dr. Xu Xiang;Dr. Bing Zhang;Dr. Feng Li
Chemistry – An Asian Journal 2015 Volume 10( Issue 7) pp:
Publication Date(Web):
DOI:10.1002/asia.201580704
Co-reporter:Cong Chao, Bing Zhang, Rui Zhai, Xu Xiang, Jindun Liu, and Rongfeng Chen
ACS Sustainable Chemistry & Engineering 2014 Volume 2(Issue 3) pp:396
Publication Date(Web):July 31, 2013
DOI:10.1021/sc400199v
Inorganic nanostructures and their assemblies play important roles in immobilizing biomolecules. Herein, we developed a facile and green methodology to assemble natural halloysite nanotubes (1D building blocks) into nest-like porous microspheres (3D architecture). We further modified the microspheres with dopamine to form a biomimetic entity. The interconnected and hierarchical pores within the microspheres provide larger pore volume to entrap biomolecules, and the abundant functional groups on the pore surface bond covalently with enzyme to enhance the immobilization ability. The porous microspheres showed excellent loading capacity for laccase immobilization as high as 311.2 mg/g, around 30 times higher than the individual halloysite nanotubes (11.3 mg/g). The specific activity above 80% was retained for the immobilized laccase compared to the free laccase. In addition, the immobilized enzyme exhibited remarkable thermal and recycle use stability. The biomimetic microspheres are expected to be biologically safe and chemically stable microcapsules for immobilizing a variety of biomolecules because of their natural and biofriendly characteristics.Keywords: Dopamine; Enzyme immobilization; Halloysite; Natural nanotubes; Porous microspheres; Self-assembly
Co-reporter:Lu Zhang, Wanhong He, Xu Xiang, Ying Li and Feng Li
RSC Advances 2014 vol. 4(Issue 82) pp:43357-43365
Publication Date(Web):14 Aug 2014
DOI:10.1039/C4RA07082H
High-efficiency and Earth-abundant electrocatalysts for the oxidation of water are required in the production of clean energy from the electrolysis or photolysis of water. Spinel Co3O4 microcrystals with a windmill shape were grown on a flexible metal substrate. The microcrystals were then roughened by a surface impregnation treatment. A secondary nanostructure grew out of the blades of the windmills to form a micro/nano hierarchical structure. The as-grown micro/nano Co3O4 had an excellent electrochemical performance in the oxidation of water. The onset overpotential of the micro/nano Co3O4 electrocatalyst for the oxidation of water was about 0.29 V in alkaline solution and the overpotential of the optimum Co3O4 electrocatalyst was 0.41 V at a current density of 10 mA cm−2. These results suggest that the electrochemical performance is associated with the roughness and active surface of the Co3O4 electrodes. The turnover frequency of the optimized Co3O4 reached 0.39 s−1 at an overpotential of 0.6 V, about 1.4 times higher than that for the pristine Co3O4 microcrystals. The turnover frequency of micro/nano Co3O4 is higher than, or comparable to, that previously reported for high-efficiency nanosized Co3O4 in alkaline solution. Stability tests indicated that these micro/nano Co3O4 electrocatalysts were highly durable towards the oxidation of water, with no structural change and no decrease in noticeable activity after operating for 12 h in oxygen-evolving reactions. This work verifies the contribution of surface roughness and an active surface to the electrochemical oxidation of water by the design of an optimum micro/nano Co3O4 electrocatalyst. Our current understanding of the catalytic role of a specific micro/nano structure is also strengthened.
Co-reporter:Yanqun Tang ; Wanhong He ; Yanluo Lu ; John Fielden ; Xu Xiang ;Dongpeng Yan
The Journal of Physical Chemistry C 2014 Volume 118(Issue 44) pp:25365-25373
Publication Date(Web):October 16, 2014
DOI:10.1021/jp5092174
Host–guest photofunctional materials have received much attention recently due to their potential applications in light emitting diodes, polarized emission, and other optoelectronic fields. In this work, we report the encapsulation of a photoactive ruthenium-based complex (4,4′-diphosphonate-2,2′-bipyridine) into the biphenyl-based metal–organic framework (MOF) as a host–guest material toward potential photofunctional applications. The resulting material (denoted as Ru@MOF) presents different two-color blue/red luminescences at the crystal interior and exterior as detected by three-dimensional confocal fluorescence microscopy. Additionally, up-conversion emission and an enhanced photoluminescence lifetime relative to the pristine Ru-based complex can also be observed in this Ru@MOF system. Upon attaching on the rutile TiO2 nanoarray, the Ru@MOF also exhibits alternated photoelectrochemical properties relative to the pristine complex. Moreover, a density functional theoretical calculation was performed on the Ru@MOF structure to provide understanding of the host–guest interactions. Based on the combination of experimental and theoretical studies on the Ru@MOF system, the aim of this work is to deeply investigate how the host–guest materials can present different photofunctionalities and optoelectronic properties compared with those of the individual components, and to give detailed information on the potential host–guest energy/electronic transfer between the MOF and the complex.
Co-reporter:Cong Chao, Jindun Liu, Jingtao Wang, Yanwu Zhang, Bing Zhang, Yatao Zhang, Xu Xiang, and Rongfeng Chen
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 21) pp:10559
Publication Date(Web):October 4, 2013
DOI:10.1021/am4022973
Halloysite nanotubes (HNTs) have been proposed as a potential support to immobilize enzymes. Improving enzyme loading on HNTs is critical to their practical applications. Herein, we reported a simple method on the preparation of high-enzyme-loading support by modification with dopamine on the surface of HNTs. The modified HNTs were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses. The results showed that dopamine could self-polymerize to adhere to the surface of HNTs and form a thin active coating. While the prepared hybrid nanotubes were used to immobilize enzyme of laccase, they exhibited high loading ability of 168.8 mg/g support, which was greatly higher than that on the pristine HNTs (11.6 mg/g support). The immobilized laccase could retain more than 90% initial activity after 30 days of storage and the free laccase only 32%. The immobilized laccase could also maintain more than 90% initial activity after five repeated uses. In addition, the immobilized laccase exhibited a rapid degradation rate and high degradation efficiency for removal of phenol compounds. These advantages indicated that the new hybrid material can be used as a low-cost and effective support to immobilize enzymes.Keywords: dopamine; enzyme immobilization; halloysite nanotubes; laccase; modification;
Co-reporter:Xu Xiang, Wanhong He, Lisha Xie and Feng Li
Catalysis Science & Technology 2013 vol. 3(Issue 10) pp:2819-2827
Publication Date(Web):31 Jul 2013
DOI:10.1039/C3CY00437F
Hydrotalcite-supported platinum nanocrystals (Pt NCs) were synthesized by a facile solution chemistry method, and then applied as an efficient catalyst for the selective hydrogenation of cinnamaldehyde (CMA) in neat water. The reduction of metal precursor ions was achieved in an aqueous solution at a low temperature (323 K), simultaneously accompanied by the crystallization of the hydrotalcite support. The size of the Pt NCs can be delicately tuned by the relative ratio of surfactant to metal precursor ions, and characterized by HRTEM and CO-adsorption infrared spectroscopy. The Pt particle sizes are closely associated with the hydrogenation selectivity toward cinnamyl alcohol (CMO), with a higher selectivity up to 85% over the larger-sized Pt in an aqueous medium. The effects of alkali (NaOH) on the catalytic performance were explored. The findings indicated that the addition of alkali enhances the selectivity toward CMO (to 90%). The catalysts showed high stability with a marginal decrease in activity and selectivity after repeated use. The hydrogenation products could be easily separated from the solvent by simple extraction, which is a greener and more convenient process than those using organic solvents.
Co-reporter:Zongmin Tian, Xu Xiang, Lisha Xie, and Feng Li
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 1) pp:288-296
Publication Date(Web):December 12, 2012
DOI:10.1021/ie300847j
The gold nanocrystals supported over CeO2-containing mixed-metal oxides were synthesized by a reduction–deposition approach followed by calcination. The zerovalent Au0 was obtained from the reduction of Au3+ ion by the hydrolysis of sucrose in an aqueous solution. The thermal post-treatment led to supported gold catalysts, in which Au nanoparticles with adjustable sizes were anchored onto the mixed oxides. The incorporation of cerium (Ce) into the support remarkably enhanced the selectivity toward C═C bond (hydrocinnamaldehyde, HCAL, ca. 83%) in cinnamaldehyde hydrogenation than the catalyst with no cerium (ca. 42%) under a high conversion (above 91%). The enhancement of selectivity to HCAL could be attributed to the decreasing sizes of Au and/or CeO2, the morphology effect of Au, and the interaction of Au and CeO2 components in the support, revealed by XRD, HRTEM, and XPS. The increasing Ce3+ amount in the catalysts leads to more oxygen vacancies. The surface electron density of Au diminishes due to the presence of oxygen vacancies. The morphological and electronic aspects of Au particles result in favorable adsorption of C═C bond versus C═O bond. A control experiment showed that the Au/CeO2 catalyst has a relatively low activity and selectivity under the identical reaction conditions. This finding indicated that a better dispersion and decreased size of CeO2 in the mixed oxides could be the key factors to enhancing the selectivity of supported Au catalysts.
Co-reporter:Xu Xiang, Shi-biao Xiang, Zheng Wang, Xia Wang, Guang Hua
Materials Letters 2012 Volume 88() pp:27-29
Publication Date(Web):1 December 2012
DOI:10.1016/j.matlet.2012.08.049
The photo-responsive behaviors of energetic materials (metal/oxidant) supported by CNTs were investigated under a common photoflash. The remarkable ignition (and/or combustion) was observed in the metal/oxidant/CNT composite with an appropriate ratio, while no obvious change was found in the absence of CNT under the identical flash conditions. The structural characterization indicated that the metallic Zr was oxidized into the corresponding metal oxide (ZrO2) after ignition due to high temperature and the exposure to air ambient. The CNTs showed increased structural defects, indicated by HRTEM and Raman spectra. The enhanced photo-response can be attributed to the absorption capability of CNTs to flash energy and high thermal conductivity, leading to a rapid increase in the internal temperature of composite materials up to ignition temperature within a very short time.Graphical abstractHighlights► Energetic materials (metal/oxidant) supported by carbon nanotubes (CNTs). ► Photo-response of the composites under a photoflash. ► The proper introduction of CNTs leads to a severe ignition. ► The structural characterization of the composites after exposure to a photoflash.
Co-reporter:Zhiwei Li, Xu Xiang, Lu Bai, Feng Li
Applied Clay Science (September 2012) Volumes 65–66() pp:14-20
Publication Date(Web):September 2012
DOI:10.1016/j.clay.2012.04.028
Co-reporter:Shouli Bai, Jun Guo, Xin Shu, Xu Xiang, Ruixian Luo, Dianqing Li, Aifan Chen, Chung Chiun Liu
Sensors and Actuators B: Chemical (June 2017) Volume 245() pp:359-368
Publication Date(Web):June 2017
DOI:10.1016/j.snb.2017.01.102
Co-reporter:Zonggao Hu, Yafei Zhao, Jindun Liu, Jingtao Wang, Bing Zhang, Xu Xiang
Journal of Colloid and Interface Science (1 December 2016) Volume 483() pp:26-33
Publication Date(Web):1 December 2016
DOI:10.1016/j.jcis.2016.08.010
Co-reporter:Zonggao Hu, Yafei Zhao, Jindun Liu, Jingtao Wang, Bing Zhang, Xu Xiang
Journal of Colloid and Interface Science (1 December 2016) Volume 483() pp:26-33
Publication Date(Web):1 December 2016
DOI:10.1016/j.jcis.2016.08.010
The highly active and selective aerobic oxidation of aromatic alcohols over earth-abundant, inexpensive and recyclable catalysts is highly desirable. We fabricated herein MnO2/graphene oxide (GO) composites by a facile in-situ growth approach at room temperature and used them in selective aerobic oxidation of benzyl alcohol to benzaldehyde. TEM, XRD, FTIR, XPS and N2 adsorption/desorption analysis were employed to systematically investigate the morphology, particle size, structure and surface properties of the catalysts. The 96.8% benzyl alcohol conversion and 100% benzaldehyde selectivity over the MnO2/GO (10/100) catalyst with well dispersive ultrafine MnO2 nanoparticles (ca. 3 nm) can be obtained within 3 h under 383 K. Simultaneously, no appreciable loss of activity and selectivity occurred after recycling use up to six times. Due to their significant low cost, excellent catalytic performance, the MnO2/GO composites have huge application prospect in organic synthesis.Ultrafine MnO2 nanoparticles decorated on graphene oxide (GO) prepared by a facile in-situ growth method at room temperature showed excellent catalytic performance for aerobic oxidation of benzyl alcohol to benzaldehyde.
Co-reporter:Wanhong He, Ruirui Wang, Lu Zhang, Jie Zhu, Xu Xiang and Feng Li
Journal of Materials Chemistry A 2015 - vol. 3(Issue 35) pp:NaN17982-17982
Publication Date(Web):2015/08/05
DOI:10.1039/C5TA04105H
A BiVO4 photoanode was modified with a multi-functional layered double hydroxide (LDH) nanowall overlayer for PEC water oxidation. The composite photoanode exhibits a tremendous cathodic shift of the onset potential (∼540 mV) and more than 2-fold enhancement in the oxidation efficiency and IPCE value.
Co-reporter:Xu Xiang, Wanhong He, Lisha Xie and Feng Li
Catalysis Science & Technology (2011-Present) 2013 - vol. 3(Issue 10) pp:NaN2827-2827
Publication Date(Web):2013/07/31
DOI:10.1039/C3CY00437F
Hydrotalcite-supported platinum nanocrystals (Pt NCs) were synthesized by a facile solution chemistry method, and then applied as an efficient catalyst for the selective hydrogenation of cinnamaldehyde (CMA) in neat water. The reduction of metal precursor ions was achieved in an aqueous solution at a low temperature (323 K), simultaneously accompanied by the crystallization of the hydrotalcite support. The size of the Pt NCs can be delicately tuned by the relative ratio of surfactant to metal precursor ions, and characterized by HRTEM and CO-adsorption infrared spectroscopy. The Pt particle sizes are closely associated with the hydrogenation selectivity toward cinnamyl alcohol (CMO), with a higher selectivity up to 85% over the larger-sized Pt in an aqueous medium. The effects of alkali (NaOH) on the catalytic performance were explored. The findings indicated that the addition of alkali enhances the selectivity toward CMO (to 90%). The catalysts showed high stability with a marginal decrease in activity and selectivity after repeated use. The hydrogenation products could be easily separated from the solvent by simple extraction, which is a greener and more convenient process than those using organic solvents.
