Baihai Li

Enhanced selective CO2 adsorption on polyamine/MIL-101(Cr) composites

The global climate change induced by greenhouse gases has stimulated active research for developing efficient strategies to mitigate CO2 emission. In the present study, we prepared a series of polyamine/metal–organic framework (MOF) composites as highly selective CO2 adsorbents from a CO2/N2 mixture, which is relevant to CO2 capture in flue gas. We show that loading polyethyleneimine (PEI) into MIL-101(Cr) frameworks can significantly enhance the selective CO2 adsorption capacity at low pressure and ambient temperature. Further, the comparative study reveals that both the particle size of the MOF and the molecular-weight of PEI play an important role in the CO2 capture ability. Regarding the particle size, smaller MIL-101(Cr) particles can facilitate the loading of PEI into the inner pores and result in lower surface area/pore volume. Thus, the resulting PEI/MIL-101(Cr) composites possess lower CO2 adsorption capacity, but are compensated by higher selectivity of CO2 over N2. On the other hand, lower molecular-weight linear PEI could readily diffuse into the inner pores and effectively block the N2 adsorption. As a result, the as-prepared A-PEI-300 sample in this work exhibits an excellent CO2 uptake of 3.6 mmol g−1 and ultrahigh CO2/N2 selectivity at 0.15 bar and 25 °C. In contrast, the higher molecular-weight branched PEI is advantageous at elevated temperature, since the composites can retain high CO2 adsorption capacity owing to the large amount of primary amine groups. Overall, polyamine/MOF composites are shown to be good candidate adsorbents for CO2 capture from flue gas. To achieve the optimal CO2 capture ability, comprehensive optimization of the polyamine and MOF structures should be performed.

Water-Free Titania-Bronze Thin Films With Superfast Lithium Ion Transport

Using pulsed laser deposition, TiO2 (-) B and its recently discovered variant Ca:TiO2 (-) B (CaTi5O11) are synthesized as highly crystalline thin films for the first time by a completely water-free process. Significant enhancement in the Li-ion battery performance is achieved by manipulating the crystal orientation of the films, used as anodes, with a demonstration of extraordinary structural stability under extreme conditions.

Catalyzed activation of CO2 by a Lewis-base site in W–Cu–BTC hybrid metal organic frameworks

A metal–organic framework (MOF)-based catalyst W–Cu–BTC is designed by hybridizing highly active W ions into Cu3(BTC)2(H2O)3 (also known as Cu–BTC or HKUST-1, BTC = 1,3,5-tricarboxylate benzene) frameworks based on density functional (DFT) calculations. We show that the hybrid W–Cu node plays a pivotal role in activating CO2 according to frontier molecular orbital theory. In contrast to the Lewis-acid nature of open metal sites in most MOFs, the exposed W ion in W–Cu–BTC is identified as a Lewis-base site, evidenced by the substantial electron donation from W ion to CO2. Kinetically, the linear CO2 molecule can be readily bent by forming a CO2–W complex after overcoming a negligible activation barrier of 0.09 eV. In addition, we present calculated infrared spectra (IR) and X-Ray spectra (XPS) for reference in future experimental studies.

Prompted hydrogenation of carbon nanotubes by doping light metals

Dissociative chemisorption of H2 on the exterior wall of the (5,5) single-walled carbon nanotubes (SWCNTs) are examined using density functional theory. We show that the hydrogenation of SWCNTs can be promoted by doping light metals in the interior channel. Potassium and aluminum are identified as promising dopants, which can enhance the binding energies of H2 on the (5,5) SWCNTs by 0.5–0.7eV and reduce the H2 dissociation barriers by 0.7–1.0eV. A possible method to further improve the hydrogenation kinetics is discussed.

Spin-flip phenomena at the Co graphene Co interfaces

In the present letter, we report phenomena at the Co|Graphene|Co interfaces based on first principles calculations. The nature of Co–C–Co and Co–graphene–Co atomic bonding at the interfaces were investigated by means of density of states, electron and spin density analysis. We show that the spins are antiferromagnetic coupled across the interface via the pd-π interactions between the Gr and Co layers, as exemplified by the superexchange mechanism. As a consequence, the spin injection efficiency at the Co|Graphene|Co interfaces and junctions will be reduced.

Electromagnetic susceptibility characterization of double SOI device

Abstract Under a research project of monolithic pixel detectors, a double silicon on insulator (DSOI) structure was introduced based on fully depleted SOI (FDSOI) technology. It not merely integrates the sensor and readout circuit on the same processed wafer, but also increases radiation tolerance. Electromagnetic susceptibility (EMS) is also an important reliability issue in pixel detectors. The readout circuit should avoid false signal generation due to coupled noise from the substrate. This paper evaluates the performance of DSOI devices regarding total ionizing dose (TID) effect compensation in transistors by applying a negative bias to the middle silicon layer, and evaluates the electromagnetic susceptibility of the substrate by a ring oscillator. The experiment results show that the DSOI device is able to compensate for TID, and the threshold voltage and leakage current are recoverable. However, the reduction of TID effect on the DSOI device is at the expense of increasing susceptibility to electromagnetic interference (EMI) on the substrate.

Atomic structure of defects and interfaces in TiO2-B and Ca:TiO2-B (CaTi5O11) films grown on SrTiO3

The bronze polymorph of titanium dioxide, TiO2-B, characterized by a crystal structure with a relatively open layered geometry, is a material of interest for various energy applications, including photovoltaics, catalysts, and high-rate energy storage devices. The related phase, CaTi5O11, which serves as an effective template layer, when deposited on (100) SrTiO3, for the growth of high quality single crystalline films of TiO2-B, is also of interest for such applications. For both materials, a detailed understanding of the film growth and defect structure is deemed critical to the successful realization of these applications in thin film devices. Thus, using results obtained with aberration-corrected transmission electron microscopy, we present an analysis of the defects and interfacial structure in CaTi5O11 films grown on (100) and (110) SrTiO3 substrates, as well as in the TiO2-B film grown on (001) CaTi5O11.

Surface-termination-dependent Pd bonding and aggregation of nanoparticles on LaFeO3 (001)

The bonding and morphology of Pd clusters deposited on the LaO- and FeO2-terminated LaFeO3 (001) surface were studied using periodic density functional methods together with scanning transmission electron microscopy. We show that Pd tends to aggregate to three-dimensional (3D) clusters on both terminations since the Pd-Pd cohesive energy is larger than the Pd-LaFeO3 adhesive energy. However, from the kinetic point of view, Pd migration on the LaO termination is facile, while stronger interactions between Pd and the FeO2 termination significantly hinder the migration of Pd. Furthermore, molecular dynamics simulations demonstrate that Pd would agglomerate into 3D metallic and PdOx particles on the LaO and FeO2 terminations, respectively, and hint at the possibility of partial penetration of the PdOx particles into the surface, as observed experimentally.

Microcontroller susceptibility variations to EFT burst during accelerated aging

Abstract With deterioration of the electromagnetic environment, microcontroller unit (MCU) electromagnetic susceptibility (EMS) to transient burst interference has become a focus of academia and enterprise. Most electromagnetic compatibility (EMC) studies of MCUs have not taken the effects of aging into account. However, component aging can degrade the physical parameters of an MCU and change its immunity to EMI. This paper proposes a time-equivalent interval accelerated aging methodology combining DC electrical and high temperature stresses. The test results show variations in susceptibility to electrical fast transients (EFT) burst revealing increasing susceptibility. The reasons for MCU immunity drifts in the aging process are discussed.

A first-principles study of CO oxidation by surface oxygen on Pt-incorporated perovskite catalyst (CaPtxTi1−xO3)

In the present work, we investigated the structural and catalytic properties of a prototype system Pt-doped CaTiO3 by means of first principles calculations. We paid particular attention to the aggregation and penetration of Pt on different surfaces of CaTiO3, and subsequent CO oxidation by surface oxygen atoms on Pt-doped CaTiO3. Our calculations indicate that CO oxidation can potentially take place when Pt is doped on the first layer of CaTiO3(001). The activation barriers are calculated to be 0.20–0.45 eV. The possibly induced O vacancy on the surface will produce a magnetic behavior by breaking the spin density symmetry due to one Pt–O bond cleavage. Our study is expected to provide an insight into the catalytic behavior of Pt ions in Pt-doped perovskite toward the oxidation of exhaust gas.