Ming-Jian Zhang

Bio: Ming-Jian Zhang is an academic researcher from Peking University. The author has contributed to research in topics: Materials science & Cathode. The author has an hindex of 31, co-authored 104 publications receiving 2585 citations. Previous affiliations of Ming-Jian Zhang include Brookhaven National Laboratory & University of Chicago.

Two phases of Ga2S3: promising infrared second-order nonlinear optical materials with very high laser induced damage thresholds

Abstract: Two phases of Ga2S3 with different space groups Cc and F3m were synthesized in pure phase by a facile boron–sulfur–metallic oxide reaction. They both have a good transparency in the wavelength range of 0.44–25 μm and exhibit comparatively large second-harmonic generation (SHG) effects of about 0.7 and 0.5 times that of commercial KTiOPO4 (KTP), for the monoclinic and cubic Ga2S3 respectively. The monoclinic Ga2S3 is phase-matchable at the wavelength of 1910 nm while the cubic phase is non-phase-matchable. In order to study their powder laser induced damage threshold (LIDT) properties, a single pulse powder LIDT measurement method was proposed and it was found that they have very high powder LIDTs of about 30 and 100 times that of AgGaS2 (AGS), respectively for the monoclinic and cubic phase, under a single pulse 1064 nm laser radiation with a pulse width τp of 8 ns. To gain further insights into the nonlinear optical (NLO) and LIDT properties of the monoclinic and cubic Ga2S3, calculations of second-order NLO susceptibility and lattice energy density (LED) were also performed to explain their SHG efficiencies and high LIDTs.

High-Performance and Long-Lived Cu/SiO2 Nanocatalyst for CO2 Hydrogenation

Abstract: Cu-based nanocatalysts have been widely used for CO2 hydrogenation, but their poor stability is the bottleneck for further industrial applications. A high-performance and long-lived Cu/SiO2 nanocatalyst was synthesized by an ammonia-evaporation method for CO2 hydrogenation. The conversion of CO2 reaches up to 28%, which is close to the equilibrium conversion of CO2 (30%), and the selectivity to methanol is 21.3%, which is much higher than the equilibrium selectivity (6.6%) at 320 °C and 3.0 MPa. Furthermore, after 120 h of evaluation, the conversion can be still maintained at a high value (27%), which is much better than a Cu/SiO2 catalyst prepared by traditional impregnation. The Cu+ species has been demonstrated to be the active component for the activation and conversion of CO2. The higher ratio of Cu+/(Cu0 + Cu+) and interaction between the metal and support deriving from copper phyllosilicate are mainly responsible for the high catalytic activity and excellent stability, respectively.

Electron-transfer photochromism to switch bulk second-order nonlinear optical properties with high contrast.

Abstract: The first bulk electron-transfer photochromic compound with intrinsic second-order nonlinear optical (NLO) photoswitching properties has been synthesized. This system employs an electron-transfer photoactive asymmetric viologen ligand coordinated to a zinc(II) center.

Intrinsic ripples in graphene

Abstract: The stability of two-dimensional (2D) layers and membranes is subject of a long standing theoretical debate. According to the so called Mermin-Wagner theorem, long wavelength fluctuations destroy the long-range order for 2D crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled. These dangerous fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes making that a two-dimensional membrane can exist but should present strong height fluctuations. The discovery of graphene, the first truly 2D crystal and the recent experimental observation of ripples in freely hanging graphene makes these issues especially important. Beside the academic interest, understanding the mechanisms of stability of graphene is crucial for understanding electronic transport in this material that is attracting so much interest for its unusual Dirac spectrum and electronic properties. Here we address the nature of these height fluctuations by means of straightforward atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon. We find that ripples spontaneously appear due to thermal fluctuations with a size distribution peaked around 70 \AA which is compatible with experimental findings (50-100 \AA) but not with the current understanding of stability of flexible membranes. This unexpected result seems to be due to the multiplicity of chemical bonding in carbon.

Nitrogen-Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High-Areal-Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium-Sulfur Batteries

Abstract: As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium-sulfur (Li-S) batteries. In this paper, a mesoporous nitrogen-doped carbon (MPNC)-sulfur nanocomposite is reported as a novel cathode for advanced Li-S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verifi ed by X-ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables the behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC-sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh cm −2 with a high sulfur loading (4.2 mg S cm −2 ) and a sulfur content (70 wt%). A high areal capacity (≈3.3 mAh cm −2 ) is demonstrated by using the novel cathode, which is crucial for the practical application of Li-S batteries. It is believed that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon-sulfur composite cathodes for Li-S batteries.

Active Materials for Aqueous Zinc Ion Batteries: Synthesis, Crystal Structure, Morphology, and Electrochemistry

Abstract: Aqueous zinc ion batteries (ZIBs) are truly promising contenders for the future large-scale electrical energy storage applications due to their cost-effectiveness, environmental friendliness, intri...

Research progress of perovskite materials in photocatalysis- and photovoltaics-related energy conversion and environmental treatment.

Abstract: Meeting the growing global energy demand is one of the important challenges of the 21st century. Currently over 80% of the world's energy requirements are supplied by the combustion of fossil fuels, which promotes global warming and has deleterious effects on our environment. Moreover, fossil fuels are non-renewable energy and will eventually be exhausted due to the high consumption rate. A new type of alternative energy that is clean, renewable and inexpensive is urgently needed. Several candidates are currently available such as hydraulic power, wind force and nuclear power. Solar energy is particularly attractive because it is essentially clean and inexhaustible. A year's worth of sunlight would provide more than 100 times the energy of the world's entire known fossil fuel reserves. Photocatalysis and photovoltaics are two of the most important routes for the utilization of solar energy. However, environmental protection is also critical to realize a sustainable future, and water pollution is a serious problem of current society. Photocatalysis is also an essential route for the degradation of organic dyes in wastewater. A type of compound with the defined structure of perovskite (ABX3) was observed to play important roles in photocatalysis and photovoltaics. These materials can be used as photocatalysts for water splitting reaction for hydrogen production and photo-degradation of organic dyes in wastewater as well as for photoanodes in dye-sensitized solar cells and light absorbers in perovskite-based solar cells for electricity generation. In this review paper, the recent progress of perovskites for applications in these fields is comprehensively summarized. A description of the basic principles of the water splitting reaction, photo-degradation of organic dyes and solar cells as well as the requirements for efficient photocatalysts is first provided. Then, emphasis is placed on the designation and strategies for perovskite catalysts to improve their photocatalytic activity and/or light adsorption capability. Comments on current and future challenges are also provided. The main purpose of this review paper is to provide a current summary of recent progress in perovskite materials for use in these important areas and to provide some useful guidelines for future development in these hot research areas.

Nanostructured materials for photocatalysis

Abstract: Photocatalysis is a green technology which converts abundantly available photonic energy into useful chemical energy. With a rapid rise of flow photoreactors in the last decade, the design and development of novel semiconductor photocatalysts is happening at a blistering rate. Currently, developed synthetic approaches have allowed the design of diverse modified/unmodified semiconductor materials exhibiting enhanced performances in heterogeneous photocatalysis. In this review, we have classified the so far reported highly efficient modified/unmodified semiconductor photocatalysts into four different categories based on the elemental composition, band gap engineering and charge carrier migration mechanism in composite photocatalysts. The recent synthetic developments are reported for each novel semiconductor photocatalyst within the four different categories, namely: pure semiconductors, solid solutions, type-II heterojunction nanocomposites and Z-scheme. The motivation behind the synthetic upgrading of modified/unmodified (pure) semiconductor photocatalysts along with their particular photochemical applications and photoreactor systems have been thoroughly reviewed.