Showing papers by "Xiaobo Chen published in 2015"
TL;DR: In this paper, a critical review highlights some key factors influencing the efficiency of heterogeneous semiconductors for solar water splitting (i.e. improved charge separation and transfer, promoted optical absorption, optimized band gap position, lowered cost and toxicity, and enhanced stability and water splitting kinetics).
Abstract: There is a growing interest in the conversion of water and solar energy into clean and renewable H2 fuels using earth-abundant materials due to the depletion of fossil fuel and its serious environmental impact. This critical review highlights some key factors influencing the efficiency of heterogeneous semiconductors for solar water splitting (i.e. improved charge separation and transfer, promoted optical absorption, optimized band gap position, lowered cost and toxicity, and enhanced stability and water splitting kinetics). Moreover, different engineering strategies, such as band structure engineering, micro/nano engineering, bionic engineering, co-catalyst engineering, surface/interface engineering of heterogeneous semiconductors are summarized and discussed thoroughly. The synergistic effects of the different engineering strategies, especially for the combination of co-catalyst loading and other strategies seem to be more promising for the development of highly efficient photocatalysts. A thorough understanding of electron and hole transfer thermodynamics and kinetics at the fundamental level is also important for elucidating the key efficiency-limiting step and designing highly efficient solar-to-fuel conversion systems. In this review, we provide not only a summary of the recent progress in the different engineering strategies of heterogeneous semiconductors for solar water splitting, but also some potential opportunities for designing and optimizing solar cells, photocatalysts for the reduction of CO2 and pollutant degradation, and electrocatalysts for water splitting.
1,489 citations
TL;DR: The recent progress in the investigation of black TiO2 nanomaterials has been reviewed here, and special emphasis has been given on their fabrication methods along with their various chemical/physical properties and applications.
Abstract: In the past few decades, there has been a wide research interest in titanium dioxide (TiO2) nanomaterials due to their applications in photocatalytic hydrogen generation and environmental pollution removal. Improving the optical absorption properties of TiO2 nanomaterials has been successfully demonstrated to enhance their photocatalytic activities, especially in the report of black TiO2 nanoparticles. The recent progress in the investigation of black TiO2 nanomaterials has been reviewed here, and special emphasis has been given on their fabrication methods along with their various chemical/physical properties and applications.
1,103 citations
TL;DR: In this article, a three-dimensional core/shell Co/Co3O4 nanosheets composed of a metallic cobalt core and an amorphous cobalt oxide shell were used for the electrochemical hydrogen evolution reaction (HER).
Abstract: Earth-abundant, low-cost electrocatalysts with outstanding catalytic activity in the electrochemical hydrogen evolution reaction (HER) are critical in realizing the hydrogen economy to lift our future welfare and civilization. Here we report that excellent HER activity has been achieved with three-dimensional core/shell Co/Co3O4 nanosheets composed of a metallic cobalt core and an amorphous cobalt oxide shell. A benchmark HER current density of 10 mA cm(-2) has been achieved at an overpotential of ∼90 mV in 1 M KOH. The excellent activity is enabled with the unique metal/oxide core/shell structure, which allows high electrical conductivity in the core and high catalytic activity on the shell. This finding may open a door to the design and fabrication of earth-abundant, low-cost metal oxide electrocatalysts with satisfactory hydrogen evolution reaction activities.
461 citations
TL;DR: In this article, the authors proposed that the synergistic effect between the Ni core and the amorphous NiO shell can accelerate both Volmer and Heyrovsky processes to drive HER at low overpotentials.
229 citations
TL;DR: This design dramatically improves ORR activity, enhances fuel cell output (200-300% power improvement), and enables superior stability (no observed degradation within 500 h of operation) from 600 to 800 °C.
Abstract: Reluctant oxygen-reduction-reaction (ORR) activity has been a long-standing challenge limiting cell performance for solid oxide fuel cells (SOFCs) in both centralized and distributed power applications. We report here that this challenge has been tackled with coloading of (La,Sr)MnO3 (LSM) and Y2O3 stabilized zirconia (YSZ) nanoparticles within a porous YSZ framework. This design dramatically improves ORR activity, enhances fuel cell output (200–300% power improvement), and enables superior stability (no observed degradation within 500 h of operation) from 600 to 800 °C. The improved performance is attributed to the intimate contacts between nanoparticulate YSZ and LSM particles in the three-phase boundaries in the cathode.
146 citations
TL;DR: It is demonstrated that ZnO and TiO2 nanoparticles can be fabricated as good microwave absorbers using a 2D electron gas plasma resonance at the disorder/order interface generated by a hydrogenation process, paving the way for new applications for wide bandgap semiconductors, especially in the μeV regime.
Abstract: Electromagnetic interactions in the microelectronvolt (μeV) or microwave region have numerous important applications in both civil and military fields, such as electronic communications, signal protection, and antireflective coatings on airplanes against microwave detection. Traditionally, nonmagnetic wide-bandgap metal oxide semiconductors lack these μeV electronic transitions and applications. Here, we demonstrate that these metal oxides can be fabricated as good microwave absorbers using a 2D electron gas plasma resonance at the disorder/order interface generated by a hydrogenation process. Using ZnO and TiO2 nanoparticles as examples, we show that large absorption with reflection loss values as large as −49.0 dB (99.99999%) is obtained in the microwave region. The frequency of absorption can be tuned with the particle size and hydrogenation condition. These results may pave the way for new applications for wide bandgap semiconductors, especially in the μeV regime.
99 citations
TL;DR: In this paper, the authors reported that hydrogenation has largely improved the microwave absorption of BaTiO3 nanoparticles, which is attributed to the increased resonance of polar rotations with the incident electromagnetic field which is amplified by the increased interfacial polarization caused by the built-in electrical field along the boundaries between different grains created within these nanoparticles.
Abstract: Microwave absorbing materials (MAMs) have numerous important applications in electronic communications, signal protection, radar dodging, etc. Although it has been proposed as a promising MAM, BaTiO3 has a high reflection coefficient at the interface with air, causing a large reflection. Thus, its efficiency of microwave absorption is not satisfactory. Here, we report that hydrogenation has largely improved the microwave absorption of BaTiO3 nanoparticles. Hydrogenation is performed on BaTiO3 nanoparticles by treating pristine BaTiO3 nanoparticles at 700 °C for 4 hours in a pure H2 environment. The enhanced microwave absorption efficiency with a reflection loss value (−36.9 dB) is attributed to the increased resonance of polar rotations with the incident electromagnetic field which is amplified by the increased interfacial polarization caused by the built-in electrical field along the boundaries between different grains created within these nanoparticles.
97 citations
TL;DR: The ultrathin tungsten oxide nanowires exhibited a high photocatalytic activity for the degradation of Rhodamine B under visible light, likely due to their enhanced visible-light absorption and the presence of oxygen vacancies as discussed by the authors.
Abstract: Ultrathin tungsten oxide nanowires with diameter of around 1.1 nm have been fabricated through a simple oleylamine (OA) assisted nonhydrolytic process. In the process, the amount of OA, reaction temperature and time impacted on controlling the formation of tungsten oxide ultrathin nanowires. At high W/OA molar ratios (>1 : 1), oriented attachment of OA molecules resulted in the preferential growth of nanowires along the [001] direction. At low W/OA molar ratios, small nanoparticles self-assembled into ultrathin nanowires. The ultrathin tungsten oxide nanowires exhibited a high photocatalytic activity for the degradation of Rhodamine B under visible light, likely due to their enhanced visible-light absorption and the presence of oxygen vacancies.
89 citations
TL;DR: In this paper, the authors present a concise overview of past research efforts on TiO2 nanomaterials as anode materials for Li-ion rechargeable batteries, focusing on research examples that illustrate the importance of the nanometer-scale, shape, dimensionality, and morphology of the titanium dioxide (TiO2) materials to their electrochemical properties for Li ion storage.
Abstract: With the increased focus on sustainable energy, Li-ion rechargeable batteries are playing more important roles in energy storage and utilization. Owing to their high safety, low cost, and moderate capacity, titanium dioxide (TiO2) nanomaterials have been considered as promising alternative anode materials for Li-ion rechargeable batteries. Here, we present a concise overview of past research efforts on TiO2 nanomaterials as anode materials for Li-ion rechargeable batteries. We focus on research examples that illustrate the importance of the nanometer-scale, shape, dimensionality, and morphology of the TiO2 nanomaterials to their electrochemical properties for Li-ion storage. Representative examples are given for nanoparticles, nanowires, nanotubes, nanosheets, and three-dimensional materials, as well as amorphous structures. Approaches to improve the performance of TiO2 nanomaterials such as carbon coating, bulk doping, self-structural modification, and compositing are surveyed briefly. Progress in the use of TiO2 nanomaterials in full-cell configurations is also reviewed. Finally, the challenges for the practical applications of TiO2 nanomaterials in Li-ion rechargeable batteries are discussed briefly.
74 citations
14 Jun 2015
TL;DR: In this article, the up-to-date developments of TiO2 nanomaterials are discussed, focusing on their synthesis and also covering their properties, modifications, and applications.
Abstract: As a versatile material of photocatalytic properties, low cost, good biocompatibility, and high chemical stability, titanium dioxide (TiO2), especially at the nanometer scale, have been investigated extensively and intensively in applications from energy and environment to health. To date, various preparation methods have been developed to synthesize TiO2 nanomaterials with well-controlled shape (e.g., nanorod, nanowire, and nanotube) and desired properties. This article briefly introduces the up-to-date developments of TiO2 nanomaterials. It focuses on their synthesis and also covers their properties, modifications, and applications.
Keywords:
titanium dioxide;
nanomaterials;
synthesis;
modification;
application
73 citations
TL;DR: In the past few decades, there has been a wide research interest in titanium dioxide (TiO2) nanomaterials due to their applications in photocatalytic hydrogen generation and environmental pollution removal.
Abstract: In the past few decades, there has been a wide research interest in titanium dioxide (TiO2) nanomaterials due to their applications in photocatalytic hydrogen generation and environmental pollution removal. Improving the optical absorption properties of TiO2 nanomaterials has been successfully demonstrated to enhance their photocatalytic activities, especially in the report of black TiO2 nanoparticles. The recent progress in the investigation of black TiO2 nanomaterials has been reviewed here, and special emphasis has been given on their fabrication methods along with their various chemical/physical properties and applications.
TL;DR: The Ag2S/Ag2Mo3O10 nanoheterostructure enhances the photocatalytic activity on the degradations of Rhodamine B and glyphosate under visible light due to the improved absorption of visible light and effective separation of charge carriers in the nano heterostructure.
Abstract: Ag2Mo3O10 nanorods decorated with Ag2 S nanoparticles have been synthesized by an anion-exchange route. With thiourea as the sulfur source, sulfur ions replace [Mo3O10](2-) units of active sites on the surface of Ag2Mo3O10 nanorods, forming Ag2Mo3O10 nanorods decorated with Ag2S nanoparticles. This induces enhanced absorption in the visible-light region. Ag2 S nanoparticles decorate the surface of Ag2Mo3O10 nanorods uniformly with a suitable amount of thiourea. The Ag2S/Ag2Mo3O10 nanoheterostructure enhances the photocatalytic activity on the degradations of Rhodamine B and glyphosate under visible light. This enhancement is attributed to the improved absorption of visible light and effective separation of charge carriers in the nanoheterostructure. Meanwhile, the Ag2S/Ag2Mo3O10 nanoheterostructure displays good photocatalytic stability based on cyclic photocatalytic experiments.
TL;DR: The chiral stationary phase for high-performance black titanium dioxide nanomaterials shows good chiral recognition ability and high uniformity tosilicon dioxide, which is a promising property for nanofiltration of titanium dioxide.
Abstract: Correction for ‘Black titanium dioxide (TiO2) nanomaterials’ by Xiaobo Chen et al., Chem. Soc. Rev., 2015, DOI: 10.1039/c4cs00330f
01 Aug 2015
TL;DR: In this paper, the authors found that the reaction temperature plays an important role in the formation and photocatalytic activity of TiO2 nanosheets, and the best performance in hydrogen generation was achieved with synergistic effects between TiO 2 nanoparticles and TiOF2 particles.
Abstract: The rapid depletion of fossil fuel reserves has triggered an urgent need for developing clean energy solutions, for example, using sunlight to produce hydrogen with benign photocatalysts. The discovery of (001) faceted TiO2 has inspired intensive studies of this model photocatalyst. Here, we found that the reaction temperature plays an important role in the formation and photocatalytic activity of TiO2 nanosheets. Small anatase TiO2 nanoparticles are formed at low temperatures, large anatase TiO2 nanosheets appear along with some TiOF2 crystals as the temperature increases, and pure (001) faceted TiO2 nanosheets are formed at high temperatures. The photocatalytic activity of the TiO2 nanoparticles/nanosheets in hydrogen generation increases when the temperature increases. The (001) facet of TiO2 shows better photocatalytic activity over other facets, and the best performance in hydrogen generation is achieved with synergistic effects between TiO2 nanosheets and TiOF2 particles.
TL;DR: This study proposes an energetic-beam controlled growth method that not only significantly lowers the growth temperature but also makes it possible to grow high-quality graphene with the desired size and patterns directly on the SiC substrate.
Abstract: Thermal decomposition of single-crystal SiC is one of the popular methods for growing graphene. However, the mechanism of graphene formation on the SiC surface is poorly understood, and the application of this method is also hampered by its high growth temperature. In this study, based on the ab initio calculations, we propose a vacancy assisted Si–C bond flipping model for the dynamic process of graphene growth on SiC. The fact that the critical stages during growth take place at different energy costs allows us to propose an energetic-beam controlled growth method that not only significantly lowers the growth temperature but also makes it possible to grow high-quality graphene with the desired size and patterns directly on the SiC substrate.
TL;DR: In this article, a novel graphene oxide-Ag-C 6 H 5 Ag 3 O 7 nanocomposite was prepared by a facile precipitation reaction with the aid of photo-reduction.