Feb. 2018-Present: Postdoctoral Research Associate in Center for Clean Energy Technology, School of Mathematical an Physical Sciences, Faculty of Science,University of Technology Sydney, Sydney, Australia
Oct. 2017-Feb. 2018: JSPS Researcher in National Institute for Materials Science (NIMS), Tsukuba, Japan
Jul. 2015-Oct. 2017: Postdoctoral Researcher in National Institute for Materials Science (NIMS), Tsukuba, Japan
Nov. 2013-Dec. 2014: Visiting Ph.D in Department of Mechanical Engineering, The University of Texas at Austin, USA
Sep. 2010-Jun. 2015: Ph.D in Materials Science and Engineering, School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, China
Sep. 2006-Jul. 2010: B.S. in Materials Chemistry, School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing, China
Can supervise: YES
1) Functional two-dimensional structures, especially 2D unilamellar nanosheets with a molecular-scale thickness;
2) Design and synthesis of 2D nanosheet-based superlattice/heterostructures;
3) Nanomaterials for advanced energy storage and conversion devices including batteries, supercapacitors, and electrocatalysis.
Tian, H, Shao, H, Chen, Y, Fang, X, Xiong, P, Sun, B, Notten, PHL & Wang, G 2019, 'Ultra-stable sodium metal-iodine batteries enabled by an in-situ solid electrolyte interphase', NANO ENERGY, vol. 57, pp. 692-702.View/Download from: Publisher's site
Xiong, P, Ma, R, Wang, G & Sasaki, T 2019, 'Progress and perspective on two-dimensional unilamellar metal oxide nanosheets and tailored nanostructures from them for electrochemical energy storage', Energy Storage Materials.View/Download from: Publisher's site
© 2018 Elsevier B.V. Research on molecularly thin two-dimensional (2D) nanosheets has experienced significant progress since the discovery of graphene. Due to the high tunability of the structure, composition, and functionality, a great number of recent studies have focused on 2D ultrathin metal oxides, which have shown promising perspectives in many fields, including electrochemical energy storage. In this review, we focus on recent advances in 2D genuine unilamellar metal oxide nanosheets delaminated from their layered parent precursors and overview nanostructured materials based on these nanosheets for electrochemical energy storage applications. In particular, new, molecular-scale integrated superlattice structures fabricated by facile solution-based strategies using 2D unilamellar metal oxide nanosheets as building blocks are highlighted as emerging electrode materials to provide ultimately enhanced performance. Finally, current opportunities and future challenges for research into 2D unilamellar metal oxide nanosheets are proposed and outlined.
Dai, F, Liu, X, Yang, T, Qian, J, Li, Y, Gao, Y, Xiong, P, Ou, H, Wu, J, Kanehara, M, Minari, T & Liu, C 2019, 'Fabrication of Two-Dimensional Crystalline Organic Films by Tilted Spin Coating for High-Performance Organic Field-Effect Transistors', ACS APPLIED MATERIALS & INTERFACES, vol. 11, no. 7, pp. 7226-7234.View/Download from: Publisher's site
Xiong, P, Zhang, X, Wan, H, Wang, S, Zhao, Y, Zhang, J, Zhou, D, Gao, W, Ma, R, Sasaki, T & Wang, G 2019, 'Interface Modulation of Two-Dimensional Superlattices for Efficient Overall Water Splitting.', Nano letters.View/Download from: Publisher's site
Molecular-scale modulation of interfaces between different unilamellar nanosheets in superlattices is promising for efficient catalytic activities. Here, three kinds of superlattices from alternate restacking of any two of the three unilamellar nanosheets of MoS2, NiFe-layered double hydroxide (NiFe-LDH), and graphene are systematically investigated for electrocatalytic water splitting. The MoS2/NiFe-LDH superlattice exhibits a low overpotential of 210 and 110 mV at 10 mA cm-2 for oxygen evolution reaction (OER) and alkaline hydrogen evolution reaction (HER), respectively, superior than MoS2/graphene and NiFe-LDH/graphene superlattices. High activity and stability toward the overall water splitting are also demonstrated on the MoS2/NiFe-LDH superlattice bifunctional electrocatalyst, outperforming the commercial Pt/C-RuO2 couple. This outstanding performance can be attributed to optimal adsorption energies of both HER and OER intermediates on the MoS2/NiFe-LDH superlattice, which originates from a strong electronic coupling effect at the heterointerfaces. These results herald the interface modulation of superlattices providing a promising approach for designing advanced electrocatalysts.
Zhao, Y, Zhang, J, Wu, W, Guo, X, Xiong, P, Liu, H & Wang, G 2018, 'Cobalt-doped MnO2 ultrathin nanosheets with abundant oxygen vacancies supported on functionalized carbon nanofibers for efficient oxygen evolution', Nano Energy, vol. 54, pp. 129-137.View/Download from: UTS OPUS or Publisher's site
© 2018 Elsevier Ltd Developing low-cost and efficient catalysts for oxygen evolution reactions (OER) with both excellent activity and robust stability remains a great challenge. Herein, we report a facile spontaneous redox reaction to grow cobalt-doped MnO2 ultrathin nanosheets in situ with abundant oxygen vacancies vertically aligned on cobalt/nitrogen co-functionalized carbon nanofibers (Co-MnO2|OV) as an efficient OER catalyst. It is confirmed that metallic cobalt plays a critical role in the formation of long and ultrathin MnO2 nanosheets during the redox reaction. Furthermore, the cobalt ions doped into MnO2 significantly enhance the catalytic activity of MnO2 nanosheets. Benefiting from the collaborative advantages of doping strategy, fast charge transfer kinetics and strong synergistic coupling effects, Co-MnO2|OV composites exhibit an excellent catalytic activity and a good durability for electrochemical water oxidation, reaching 10 mA cm−2 at an overpotential of 279 mV. According to the density functional theory (DFT) calculations, the enhanced catalytic activity mainly originates from a better conductivity and the decreased adsorption energy barrier of OH- on the O sites neighboring the doped Co and oxygen vacancies. Our findings suggest that the control over the structure and composition of the materials can achieve highly efficient oxygen evolution electrocatalysts.
Xiong, P, Ma, R, Sakai, N, Nurdiwijayanto, L & Sasaki, T 2018, 'Unilamellar Metallic MoS2/Graphene Superlattice for Efficient Sodium Storage and Hydrogen Evolution', ACS Energy Letters, vol. 3, no. 4, pp. 997-1005.View/Download from: UTS OPUS or Publisher's site
© 2018 American Chemical Society. Unilamellar metallic nanosheets possess superiority for electrochemical energy storage and conversion applications compared to the few-layered bulk and semiconducting counterparts. Here, we report the utilization of unilamellar metallic 1T phase MoS2 nanosheets for efficient sodium storage and hydrogen evolution through a MoS2/graphene superlattice. The superlattice-like assembly composed of alternately restacked unilamellar MoS2 and modified reduced graphene oxide nanosheets was prepared by a facile solution-phase direct restacking method. As an anode for sodium storage, the MoS2/graphene superlattice anode exhibited an excellent rate capability of ∼240 mA h g-1 at 51.2 A g-1 and a stable reversible capacity of ∼380 mA h g-1 after 1000 cycles at 10 A g-1. In addition, a low onset potential of ∼88 mV and a small Tafel slope of 48.7 mV decade-1 were attained for the hydrogen evolution reaction. Our findings are important for further developing the potential of 2D nanosheets for energy storage and conversion.
Xiong, P, Ma, R, Sakai, N & Sasaki, T 2018, 'Genuine Unilamellar Metal Oxide Nanosheets Confined in a Superlattice-like Structure for Superior Energy Storage', ACS NANO, vol. 12, no. 2, pp. 1768-1777.View/Download from: Publisher's site
Xiong, P, Zhang, X, Zhang, F, Yi, D, Zhang, J, Sun, B, Tian, H, Shanmukaraj, D, Rojo, T, Armand, M, Ma, R, Sasaki, T & Wang, G 2018, 'Two-Dimensional Unilamellar Cation-Deficient Metal Oxide Nanosheet Superlattices for High-Rate Sodium Ion Energy Storage.', ACS Nano, vol. 12, pp. 12337-12346.View/Download from: Publisher's site
Cation-deficient two-dimensional (2D) materials, especially atomically thin nanosheets, are highly promising electrode materials for electrochemical energy storage that undergo metal ion insertion reactions, yet they have rarely been achieved thus far. Here, we report a Ti-deficient 2D unilamellar lepidocrocite-type titanium oxide (Ti0.87O2) nanosheet superlattice for sodium storage. The superlattice composed of alternately restacked defective Ti0.87O2 and nitrogen-doped graphene monolayers exhibits an outstanding capacity of ∼490 mA h g-1 at 0.1 A g-1, an ultralong cycle life of more than 10000 cycles with ∼0.00058% capacity decay per cycle, and especially superior low-temperature performance (100 mA h g-1 at 12.8 A g-1 and -5 °C), presenting the best reported performance to date. A reversible Na+ ion intercalation mechanism without phase and structural change is verified by first-principles calculations and kinetics analysis. These results herald a promising strategy to utilize defective 2D materials for advanced energy storage applications.
Peng, L, Xiong, P, Ma, L, Yuan, Y, Zhu, Y, Chen, D, Luo, X, Lu, J, Amine, K & Yu, G 2017, 'Holey two-dimensional transition metal oxide nanosheets for efficient energy storage', Nature Communications, vol. 8.View/Download from: Publisher's site
© The Author(s) 2017. Transition metal oxide nanomaterials are promising electrodes for alkali-ion batteries owing to their distinct reaction mechanism, abundant active sites and shortened ion diffusion distance. However, detailed conversion reaction processes in terms of the oxidation state evolution and chemical/mechanical stability of the electrodes are still poorly understood. Herein we explore a general synthetic strategy for versatile synthesis of various holey transition metal oxide nanosheets with adjustable hole sizes that enable greatly enhanced alkali-ion storage properties. We employ in-situ transmission electron microscopy and operando X-ray absorption structures to study the mechanical properties, morphology evolution and oxidation state changes during electrochemical processes. We find that these holey oxide nanosheets exhibit strong mechanical stability inherited from graphene oxide, displaying minimal structural changes during lithiation/delithiation processes. These holey oxide nanosheets represent a promising material platform for in-situ probing the electrochemical processes, and could open up opportunities in many energy storage and conversion systems.
Xiong, P, Ma, R, Sakai, N, Bai, X, Li, S & Sasaki, T 2017, 'Redox Active Cation Intercalation/Deintercalation in Two-Dimensional Layered MnO2 Nanostructures for High-Rate Electrochemical Energy Storage', ACS Applied Materials and Interfaces, vol. 9, no. 7, pp. 6282-6291.View/Download from: Publisher's site
© 2017 American Chemical Society. Two-dimensional (2D) layered materials with a high intercalation pseudocapacitance have long been investigated for Li+-ion-based electrochemical energy storage. By contrast, the exploration of guest ions other than Li+ has been limited, although promising. The present study investigates intercalation/deintercalation behaviors of various metal ions in 2D layered MnO2 with various interlayer distances, K-birnessite nanobelt (K-MnO2), its protonated form (H-MnO2), and a freeze-dried sample of exfoliated nanosheets. Series of metal ions, such as monovalent Li+, Na+, and K+ and divalent Mg2+, exhibit reversible intercalation during charge/discharge cycling, delivering high-rate pseudocapacitances. In particular, the freeze-dried MnO2 of exfoliated nanosheets restacked with the largest interlayer spacing and a less compact 3D network exhibits the best rate capability and a stable cyclability over 5000 cycles. Both theoretical calculation and kinetic analysis reveal that the increased interlayer distance facilitates the fast diffusion of cations in layered MnO2 hosts. The results presented herein provide a basis for the controllable synthesis of layered nanostructures for high-rate electrochemical energy storage using various single- and multivalent ions.
Xiong, P, Zhu, J, Zhang, L & Wang, X 2016, 'Recent advances in graphene-based hybrid nanostructures for electrochemical energy storage', Nanoscale Horizons, vol. 1, no. 5, pp. 340-374.View/Download from: Publisher's site
© 2016 The Royal Society of Chemistry. In recent years, graphene has emerged as a promising candidate for electrochemical energy storage applications due to its large specific surface area, high electrical conductivity, good chemical stability, and strong mechanical flexibility. Moreover, its unique two-dimensional (2D) nanostructure can be used as an ideal building block for controllable functionalization with other active components and the resulting graphene-based hybrids exhibit desirable properties for improved energy storage capability. This review summarizes the most recent progress on graphene and graphene-based hybrid nanostructures for three frontier electrochemical energy storage device applications, i.e., lithium-ion batteries, lithium-sulfur batteries and supercapacitors. Finally, we outline the future perspectives and trends in this research field including several challenges and opportunities.
Zha, D, Xiong, P & Wang, X 2015, 'Strongly coupled manganese ferrite/carbon black/polyaniline hybrid for low-cost supercapacitors with high rate capability', Electrochimica Acta, vol. 185, pp. 218-228.View/Download from: Publisher's site
© 2015 Elsevier Ltd. Hybrid nanostructures with reliable electrochemical performances (e.g., high rate capability and long cycling lifetime) and low fabrication costs are attractive for extensive application for next-generation energy storage devices. Herein, based on the inexpensive commercial carbon black (CB), a ternary manganese ferrite/carbon black/polyaniline (MCBP) hybrid is designed and synthesized through a facile two-step approach. It is found that the synergistic effects in this strongly coupled ternary hybrid nanostructure can remarkably enhance the electrochemical performances, including the impressively high rate capability (∼98% capacitance retention at a current density of as high as 40 A g-1) and excellent cycling stability (∼80% capacitance retention after 10,000 cycles at 5 A g-1). A symmetric supercapacitor is fabricated using ternary MCBP hybrid, which presents excellent rate capability (over 94% capacitance retention at 10 A g-1) and long cycle life (∼75% capacitance retention after 100,000 cycles at 5 A g-1). Such a low-cost integrated ternary hybrid is a promising electrode material for commercial applications in supercapacitors.
Xiong, P, Zhu, J & Wang, X 2015, 'Recent advances on multi-component hybrid nanostructures for electrochemical capacitors', Journal of Power Sources, vol. 294, pp. 31-50.View/Download from: Publisher's site
© 2015 Elsevier B.V. All rights reserved. With the continuously growing energy demand and ever-escalating environmental problems, the great energy transition from conventional fossil fuels to renewable sources of energy is under way, and requires more efficient and reliable electrochemical energy storage devices, such as electrochemical capacitors (also called as supercapacitors). In order to achieve high energy and power densities of supercapacitors, numerous efforts are devoted to the development of advanced multi-component hybrid electrode materials for realizing high-performance. This review summarizes the most recent progress in the development of nanostructured electrode materials for energy storage, with a particular focus on these nanostructures that integrate carbon materials, metal oxides/hydroxides and conducting polymers for enhancing energy storage performances via taking advantage of each component's unique functionality and their synergetic effects. Finally, we give some perspectives on the challenges and opportunities in this intriguing field.
Xiong, P, Peng, L, Chen, D, Zhao, Y, Wang, X & Yu, G 2015, 'Two-dimensional nanosheets based Li-ion full batteries with high rate capability and flexibility', Nano Energy, vol. 12, pp. 816-823.View/Download from: Publisher's site
© 2015 Elsevier Ltd. Here we report an all-nanosheet-based Li-ion full battery using ZnMn2O4-graphene hybrid nanosheet and LiFePO4 nanosheet as anode and cathode, respectively. The short Li ion diffusion length and open charge transport channel of these two-dimensional (2D) nanostructures enable rapid charge and discharge rate. The all-nanosheet-based full battery exhibits superior rate capability and cycling stability, compared to the control full battery using conventional graphite anode and commercial LiFePO4 cathode. Furthermore, flexible full batteries using these 2D nanostructured electrodes are fabricated in pouch cell form, and exhibit impressive electrochemical stability without structural failure and performance loss under various mechanical bending states.
Xiong, P, Liu, B, Teran, V, Zhao, Y, Peng, L, Wang, X & Yu, G 2014, 'Chemically integrated two-dimensional hybrid zinc manganate/graphene nanosheets with enhanced lithium storage capability', ACS Nano, vol. 8, no. 8, pp. 8610-8616.View/Download from: Publisher's site
Hybrid inorganic/graphene two-dimensional (2D) nanostructures can offer vastly open large surface areas for ion transport and storage and enhanced electron transport, representing a promising material platform for next-generation energy storage. Here we report chemically integrated hybrid ZnMn2O4/graphene nanosheets synthesized via a facile two-step method for greatly enhanced lithium storage capability. The hybrid 2D nanosheets are composed of ultrafine ZnMn2O4 nanocrystals with a mean diameter of ∼4 nm attached to and well dispersed on the surface of reduced graphene oxide sheets. The hybrid nanosheets based anode offers a high capacity of ∼800 mAh g-1 at a current rate of 500 mA g -1, excellent rate capability, and long-term cyclability with reversible capacity of ∼650 mAh g-1 over 1500 cycles at a current density of 2000 mA g-1. Moreover, when tested in a temperature range of ∼0-60 °C, the designed anode can maintain high discharge capacities from 570 to 820 mAh g-1. © 2014 American Chemical Society.
Xiong, P, Hu, C, Fan, Y, Zhang, W, Zhu, J & Wang, X 2014, 'Ternary manganese ferrite/graphene/polyaniline nanostructure with enhanced electrochemical capacitance performance', Journal of Power Sources, vol. 266, pp. 384-392.View/Download from: Publisher's site
A ternary manganese ferrite/graphene/polyaniline (MGP) nanostructure is designed and synthesized via a facile two-step approach. This nanostructure exhibits outstanding electrochemical performances, such as high specific capacitance (454.8 F g-1 at 0.2 A g-1), excellent rate capability (75.8% capacity retention at 5 A g-1), and good cycling stability (76.4% capacity retention after 5000 cycles at 2 A g-1), which are superior to those of its individual components (manganese ferrite, reduced-graphene oxide, polyaniline) and corresponding binary hybrids (manganese ferrite/graphene (MG), manganese ferrite/polyaniline (MP), and graphene/polyaniline (GP)). A symmetric supercapacitor device using the as-obtained hybrid has been fabricated and tested. The device exhibits a high specific capacitance of 307.2 F g-1 at 0.1 A g-1 with a maximum energy density of 13.5 W h kg-1. The high electrochemical performance of ternary MGP can be attributed to its well-designed nanostructure and the synergistic effect of the individual components. © 2014 Elsevier B.V. All rights reserved.
Xiong, P, Huang, H & Wang, X 2014, 'Design and synthesis of ternary cobalt ferrite/graphene/polyaniline hierarchical nanocomposites for high-performance supercapacitors This work is dedicated to Professor MIN Enze on the occasion of his 90th birthday.', Journal of Power Sources, vol. 245, pp. 937-946.View/Download from: Publisher's site
A ternary cobalt ferrite/graphene/polyaniline nanocomposite (CGP) is designed and fabricated via a facile two-step approach: cobalt ferrite nanoparticles dispersed on graphene sheets are achieved by a hydrothermal method, followed by coating with polyaniline (PANI) through in situ polymerization process. Electrochemical measurements demonstrate that the specific capacitance of the resulting ternary hybrid (CGP) is up to 1133.3 F g-1 at a scan rate of 1 mV s-1 and 767.7 F g-1 at a current density of 0.1 A g-1 using a three-electrode system, while 716.4 F g-1 at a scan rate of 1 mV s-1 and 392.3 F g-1 at a current density of 0.1 A g-1 using a two-electrode system, which are significantly higher than those of pure CoFe2O4, graphene and PANI, or binary CoFe 2O4/graphene, CoFe2O4/PANI and graphene/PANI hybrids. In addition, over 96% of the initial capacitance can be retained after repeating test for 5000 cycles, demonstrating a high cycling stability. The extraordinary electrochemical performance of the ternary CGP nanocomposite can be attributed to its well-designed nanostructure and the synergistic effects of the individual components. © 2013 Elsevier Ltd. All rights reserved.
Xiong, P, Zhu, J & Wang, X 2013, 'Cadmium sulfide-ferrite nanocomposite as a magnetically recyclable photocatalyst with enhanced visible-light-driven photocatalytic activity and photostability', Industrial and Engineering Chemistry Research, vol. 52, no. 48, pp. 17126-17133.View/Download from: Publisher's site
We report a facile strategy to fabricate a cadmium sulfide-ferrite (CdS-MFe2O4, M = Zn, Co) nanocomposite with differing ferrite content via a two-step hydrothermal method and demonstrate its application as a magnetically recyclable photocatalyst with enhanced visible-light-driven photocatalytic activity and photostability. The photocatalytic activities of as-prepared photocatalysts are evaluated by the degradation of rhodamine B (RhB) and 4-chlorophenol (4-CP) in aqueous solution under visible-light irradiation. Compared with pure CdS, both CdS-ZnFe 2O4 and CdS-CoFe2O4 show more broad absorption in the visible-light region, which favors the visible-light utilization for better photocatalytic performance. Moreover, the surface area of cadmium sulfide-ferrite is much higher than that of pure CdS, also resulting in enhanced photocatalytic activity. Furthermore, the synergic effects of CdS and ferrites can reduce the recombination probability of photogenerated electron-hole pairs and enhance the charge separation efficiency, leading to high photocatalytic performance and remarkable inhibited photocorrosion. © 2013 American Chemical Society.
Sun, J, Fu, Y, Xiong, P, Sun, X, Xu, B & Wang, X 2013, 'A magnetically separable P25/CoFe<inf>2</inf>O<inf>4</inf>/graphene catalyst with enhanced adsorption capacity and visible-light-driven photocatalytic activity', RSC Advances, vol. 3, no. 44, pp. 22490-22497.View/Download from: Publisher's site
A straightforward strategy is designed for the fabrication of a magnetically separable P25/CoFe2O4/graphene photocatalyst with differing P25 contents via a facile one step hydrothermal approach. TEM observations show that graphene sheets are exfoliated and decorated with well-dispersed TiO2 and CoFe2O4 nanoparticles. The adsorption capacity and visible-light-driven photocatalytic activity are evaluated in terms of the efficiencies of adsorption and photodegradation of various dyes, including methylene blue (MB), methyl orange (MO) and neutral dark yellow (DY). The evaluation results demonstrate that the P25/CoFe 2O4/graphene photocatalyst exhibits the best performance among P25/CoFe2O4/graphene (PCG), CoFe2O 4/graphene (CG), P25/CoFe2O4 (PC) and P25/graphene (PG) photocatalysts, not only in the adsorption progress, but also in the photocatalytic degradation. The significant enhancement after combination can be attributed to the synergistic effect among individual components. Furthermore, CoFe2O4 nanoparticles themselves have excellent magnetic properties, which are largely maintained in the composite, and therefore, it is no longer necessary to introduce additional magnetic supports for magnetic separation in a suspension system. © The Royal Society of Chemistry 2013.
Xiong, P, Wang, L, Sun, X, Xu, B & Wang, X 2013, 'Ternary titania-cobalt ferrite-polyaniline nanocomposite: A magnetically recyclable hybrid for adsorption and photodegradation of dyes under visible light', Industrial and Engineering Chemistry Research, vol. 52, no. 30, pp. 10105-10113.View/Download from: Publisher's site
A straightforward strategy is designed for the fabrication of magnetically recyclable ternary titania-cobalt ferrite-polyaniline (P25-CoFe 2O4-PANI) photocatalysts with differing P25/CoFe 2O4 ratio. The pseudo-second-order and Langmuir models are found to be most suitable for describing the adsorption of methyl orange (MO) onto the photocatalysts. The photocatalytic activity of P25-CoFe 2O4-PANI is evaluated by the degradation of various dyes under visible light irradiation, and the results show that the ternary P25-CoFe2O4-PANI photocatalyst exhibits high photocatalytic activity due to the good adsorption capacity of the hybrid and the introduction of P25, which can further improve the separation of the light-induced electron-hole pairs. The degradation of anionic dyes is much more effective than that of cationic dyes due to the negatively charged groups of anionic dyes undergo electrostatic attraction with the positively charged backbone of PANI, and such an effective adsorption helps in promoting the degradation. © 2013 American Chemical Society.
Xiong, P, Chen, Q, He, M, Sun, X & Wang, X 2012, 'Cobalt ferrite-polyaniline heteroarchitecture: A magnetically recyclable photocatalyst with highly enhanced performances', Journal of Materials Chemistry, vol. 22, no. 34, pp. 17485-17493.View/Download from: Publisher's site
A cobalt ferrite-polyaniline photocatalyst is successfully prepared by in situ oxidative polymerization. The excellent magnetic properties of CoFe 2O 4 are maintained in the composite to some extent, and therefore the photocatalyst can be separated easily by an external magnetic field. A significant adsorption can be observed in the case of the anionic dyes and neutral dyes because the negatively charged groups or the electron-rich groups of these dyes undergo chemical interactions with the positively charged backbone of polyaniline (PANI). Such an adsorption helps in promoting the photodegradation of the dyes. It is interesting that although CoFe 2O 4 alone is an inactive visible-light-driven photocatalyst, the combination of CoFe 2O 4 nanoparticles with PANI leads to high photocatalytic activity for the degradation of the dyes under visible light irradiation. The dramatic enhancement in photoactivity can be attributed to the excited state electrons in PANI which can migrate to the conduction band (CB) of CoFe 2O 4, and the photogenerated holes in the valence band (VB) of CoFe 2O 4 which can directly transfer to the HOMO of PANI, effectively preventing a direct recombination of electrons and holes. Due to electrostatic repulsion, the cationic dyes containing positively charged groups cannot easily gain access to the positively charged backbone of PANI, giving very low photodegradation rates. © 2012 The Royal Society of Chemistry.
Xiong, P, Fu, Y, Wang, L & Wang, X 2012, 'Multi-walled carbon nanotubes supported nickel ferrite: A magnetically recyclable photocatalyst with high photocatalytic activity on degradation of phenols', Chemical Engineering Journal, vol. 195-196, pp. 149-157.View/Download from: Publisher's site
A magnetically recyclable and highly photocatalytic NiFe 2O 4/multi-walled carbon nanotubes (NiFe 2O 4/MWNT) photocatalyst with differing MWNT content has been successfully prepared via a one-step hydrothermal method. In this study, NiFe 2O 4 is not only used as the magnetic material but also acts as the photocatalyst. It is interesting that in the presence of MWNT the poorly active nanocrystals of NiFe 2O 4 are dramatically converted into a highly active catalyst. The highly photocatalytic activities are evaluated by the degradation of phenol, o-nitrophenol (ONP), p-nitrophenol (PNP), and picric acid (PA) under ultraviolet light irradiation. The significant enhancement in photoactivity can be attributed to the synergistic effect between NiFe 2O 4 and MWNT: the effective charge transfer from NiFe 2O 4 to MWNT and thus the suppressed recombination of electron-hole pairs of the composite. Moreover, the remarkable magnetic properties of NiFe 2O 4/MWNT give a more convenient way to recycle the photocatalysts. © 2012 Elsevier B.V.
Zhang, S, Xiong, P, Yang, X & Wang, X 2011, 'Novel PEG functionalized graphene nanosheets: Enhancement of dispersibility and thermal stability', Nanoscale, vol. 3, no. 5, pp. 2169-2174.View/Download from: Publisher's site
A series of polyethylene glycol (PEG) functionalized graphene sheet hybrid materials (FGHMs) have been successfully synthesized via ester linkages. Interestingly, our products can be dispersed in both polar/protic solvents and nonpolar/nonprotic ones, which differ significantly from previously reported systems and are of great value in the wide-spread application of these "carbon nanosheet" based materials by solution-phase processing. Furthermore, the addition of PEG-modified carbon nanosheets as nanofillers significantly improves the thermal stability of the bulk polymers. In our case, an increase of 35 K in thermal stability can be obtained for PEG4000 after filling with as low as 1 wt % of the PEG modified carbon sheets, suggesting their great potential as novel nanofillers in industry. © 2011 The Royal Society of Chemistry.
Fu, Y, Xiong, P, Chen, H, Sun, X & Wang, X 2012, 'High photocatalytic activity of magnetically separable manganese ferrite - Graphene heteroarchitectures', Industrial and Engineering Chemistry Research, pp. 725-731.View/Download from: Publisher's site
A simple and straightforward strategy was developed to fabricate magnetically separable MnFe 2O 4-graphene photocatalysts with differing graphene content. It was found that graphene sheets were fully exfoliated and decorated with MnFe 2O 4 nanocrystals having an average diameter of 5.65 nm and a narrow particle size distribution. It is very interesting that, although MnFe 2O 4 alone is photocatalytically inactive under visible light irradiation, the combination of MnFe 2O 4 nanoparticles with graphene sheets leads to high photocatalytic activity for the degradation of methylene blue under visible light irradiation. The strong magnetic property of MnFe 2O 4 nanoparticles can be used for magnetic separation in a suspension system, and therefore it does not require additional magnetic components as is the usual case. Consequently, the MnFe 2O 4-graphene system becomes a dual function photocatalyst. The significant enhancement in photoactivity under visible light irradiation can be ascribed to the reduction of graphene oxide (GO), because the photogenerated electrons of MnFe 2O 4 can transfer easily from the conduction band to the reduced GO, effectively preventing a direct recombination of electrons and holes. Hydroxyl radicals play the role of main oxidant in the MnFe 2O 4-graphene system, and the radicals' oxidation reaction is obviously dominant. © 2011 American Chemical Society.