Guilin Zhuang

Enhanced role of Al or Ga-doped graphene on the adsorption and dissociation of N2O under electric field

To find an effective strategy for the capture and decomposition of nitrous oxide (N(2)O) is very important in order to protect the ozone layer and control the effects of global warming. Based on first-principles calculations, such a strategy is proposed by the systemic study of N(2)O interaction with pristine and Al (or Ga)-doped graphene, and N(2)O dissociation on the surface of Al (or Ga)-doped graphene in an applied electric field. The calculated adsorption energy value shows the N(2)O molecule more firmly adsorbs on the surface of Al (or Ga)-doped graphene than that of pristine graphene, deriving from a stronger covalent bond between the N(2)O molecule and the Al (or Ga) atom. Furthermore, our study suggests that N(2)O molecules can be easily decomposed to N(2) and O(2) with the appropriate electric field, which reveals that Al-doped graphene may be a new candidate for control of N(2)O.

Integrating cobalt phosphide and cobalt nitride-embedded nitrogen-rich nanocarbons: high-performance bifunctional electrocatalysts for oxygen reduction and evolution

The demand for cost-effective bifunctional oxygen electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) for application in rechargeable metal–air batteries and fuel cells operated in alkaline solutions has increased over the decades. We report for the first time an easy procedure for a unique nitrogen-rich sandwich-architectured catalyst (CoNP@NC/NG) as a highly efficient bifunctional electrocatalyst for ORR and OER. Physical characterizations confirmed the coexistence of Co2P and CoxN crystal phases in the nanostructure. The as-prepared CoNP@NC/NG exhibited potent bifunctional electrochemical performance with superior positive onset potential, large kinetic current density, and outstanding stability toward both ORR and OER, thereby showing excellent activities compared with Pt/C and state-of-the-art nonprecious catalysts. The excellent performance could have originated from the robust conjugation between the Co2P and CoxN crystal structures leading to a synergistic effect of the two interfaces, and the carbon shell also increased the number of nitrogen active sites. Moreover, the integrated structure of CoNP@NC/NG provided high electrical conductivity and facilitated electron transfer. Furthermore, the rechargeable zinc–air battery testing of CoNP@NC/NG-700 revealed good performance and long-term stability. The current work provided a new pathway to design bifunctional catalysts with multiple crystal phases for energy conversion and storage.

Synergistic Effect of Nitrogen in Cobalt Nitride and Nitrogen‐Doped Hollow Carbon Spheres for the Oxygen Reduction Reaction

The need for inexpensive and high‐activity oxygen‐reduction‐reaction (ORR) electrocatalysts has attracted considerable research interest over the past years. Herein, we report a novel hybrid that contains cobalt nitride/nitrogen‐rich hollow carbon spheres (CoxN/NHCS) as a high‐performance catalyst for ORR. The CoxN nanoparticles were uniformly dispersed and confined in the hollow NHCS shell. The performance of the resulting CoxN/NHCS hybrid was comparable with that of a commercial Pt/C at the same catalyst loading toward ORR, but the mass activity of the former was 5.7 times better than that of the latter. The nitrogen in both CoxN and NHCS, especially CoxN, could weaken the adsorption of reaction intermediates (O and OOH), which follows the favorable reaction pathway on CoxN/NHCS according to the DFT‐calculated Gibbs free‐energy diagrams. Our results demonstrated a new strategy for the design and development of inexpensive, nonprecious‐metal electrocatalysts for next‐generation fuels.

A superior fluorescent sensor for Al3+ and UO22+ based on a Co(II) metal–organic framework with exposed pyrimidyl Lewis base sites

A robust 3D pcu Co(II) metal–organic framework (MOF) based on a designed bent pyrimidyl–biimidazole ligand, [Co2(dmimpym)(nda)2]n (1; dmimpym = 4,6-di(2-methyl-imidazol-1-yl)-pyrimidine, H2nda = 1,4-naphthalenedicarboxylic acid), was successfully synthesized under solvothermal conditions and characterized using single-crystal X-ray diffraction. Compound 1 has a 2-fold interpenetrated 6-connected pcu network based on a [Co2(COO)4] paddle-wheel secondary building unit (SBU). It contains exposed pyrimidyl Lewis base sites, has porosity, and exhibits ligand-based blue emission in the solid state, which render it suitable as a fluorescent sensor for the detection of metal ions. Fluorescence titration experiments reveal that 1 is highly selective for Al3+ with exclusively enhanced emission as compared to other metal ions, and the limit of detection (LOD) reaches as low as 0.7 μM. Importantly, 1 can be cycled at least five times without the loss of emission signals. Moreover, 1 is able to detect low concentration of uranyl ions via fluorescence quenching. The present study sheds light on the realization of the practical application of MOFs as luminescent sensors via tailoring of the ligand and extends the way towards low-cost transition metal-based MOF sensors.

Pt@Au Nanorods Uniformly Decorated on Pyridyne Cycloaddition Graphene as a Highly Effective Electrocatalyst for Oxygen Reduction

Preparing metal-supported graphene nanocomposites is both interesting and challenging because of their well-defined morphologies and have potential application for oxygen reduction reaction (ORR). Here, we present an easy approach to synthesizing a novel hybrid material composed of Pt@Au nanorods (NRs) uniformly dispersed on the pyridyne cycloaddition of graphene (Pt@Au-PyNG), and the material serves as a high-performance catalyst for ORR. This hybrid electrocatalyst significantly decreases the use of Pt by using Pt dispersed on Au NRs and shows a markedly high activity toward ORR. The resulting Pt@Au-PyNG hybrid displayed comparable electrocatalytic activity and better stability than commercial Pt/C in alkaline solutions toward ORR. The hybrid effectively blocks CO formation to increase catalyst resistance to CO poisoning, thereby decreasing the amount of Pt needed. Free-energy diagrams for ORR on Pt@Au (111) through dissociative and associative mechanisms show that OH or O hydrogenation is the rate-limiting step based on DFT calculations.

Robust Cluster Building Unit: Icosanuclear Heteropolyoxocopperate Templated by Carbonate

The encapsulation of carbonate derived from atmospheric CO2 has resulted in an icosanuclear heteropolyoxocopperate, isolated as a metal-organic 1D chain, 2D sheet, or 3D framework, in which the Cu20 nanocluster represents the first eight-capped α-Keggin polyoxometalate with the late-transition-metal Cu(II) as the polyatom, CO3(2-) as the heteroanion, and OH(-) and suc(2-) or glu(2-) (H2suc=succinic acid; H2glu=glutaric acid) as the terminal ligands, which suggests a conceptual similarity to classical polyoxometalates. Even in the presence of competitive SO4(2-) in the assembly system, the CO3(2-) anion is still captured as a template to direct the formation of the Cu20 nanocluster, which indicates the stronger templation ability of CO3(2-) compared with SO4(2-). When other aliphatic dicarboxylates, such as glutaric acid, were used as ligands, the CO3(2-)-templated Cu20 nanocluster was maintained and acted as a cluster building unit (CBU) to be linked by two glutarate bridges to generate a distinct 1D metal-organic chain. This report presents not only a rare example of a huge anion-templated transition-metal cluster, but also its use as a robust CBU to construct novel coordination architectures. Variable-temperature magnetic susceptibility studies revealed that an antiferromagnetic interaction exists within the Cu20 nanocluster. The correlation between the coordination structure and the electron paramagnetic resonance spectra recorded of both powder and single-crystal samples are discussed in detail.

Pyridyne cycloaddition of graphene: “external” active sites for oxygen reduction reaction

“External” nitrogen doped graphene sheets via pyridyne cycloaddition were fabricated, which can serve as feasible Pt alternatives for oxygen reduction reaction electrocatalysts. Notably, the excellent ORR performance of PyNGs can be attributed to the possible adsorption and catalytic site of the ortho-carbon of “external” nitrogen.

Synergistic effect of S,N-co-doped mesoporous carbon materials with high performance for oxygen-reduction reaction and Li-ion batteries

S,N-co-doped porous carbon (SNPC) materials are good candidates for the cathodic oxygen-reduction reaction (ORR) and lithium-ion batteries (LIBs). However, SNPC gives low yield and is expensive. Herein, we report a new and efficient method for synthesizing a S,N-co-doped mesoporous carbon material through the carbonization of S,N-containing precursors in molten ZnCl2, where ZnCl2 served as the ionic solvent and Lewis acid catalyst. The resultant SNPC-800 showed a mesoporous structure with a specific surface area of 1235 m2 g−1 and a mesopore-size range of 10–45 nm, which were considerably larger than those obtained through the carbonization of ionic liquids and fabrication of graphene oxides. Furthermore, ORR measurements indicated good catalytic activity, comparable to the commercial Pt/C catalyst. Also the SNPC-800 material exhibited excellent catalytic stability, and high methanol tolerance compared to the commercial Pt/C catalyst. Density functional theory calculation results revealed that the catalytic properties originated from the synergistic effect of the S/N dopant and that the main catalytic reaction path followed an associative mechanism. LIB tests further showed high reversible capacity, as well as excellent cycling stability and rate performance.

A Large π‐Extended Carbon Nanoring Based on Nanographene Units: Bottom‐Up Synthesis, Photophysical Properties, and Selective Complexation with Fullerene C70

Herein we report the organoplatinum-mediated bottom-up synthesis, characterization, and properties of a novel large π-extended carbon nanoring based on a nanographene hexa-peri-hexabenzocoronene (HBC) building unit. This tubular structure can be considered as an example of the longitudinal extension of the cycloparaphenylene scaffold to form a large π-extended carbon nanotube (CNT) segment. The cyclic tetramer of a tetramesityl HBC ([4]CHBC) was synthesized by the reaction of a 2,11-diborylated hexa-peri-hexabenzocoronene with a platinum complex, followed by reductive elimination. The structure of this tubular molecule was further confirmed by physical characterization. Theoretical calculations indicate that the strain energy of this nanoring is as high as 49.18 kcal mol-1 . The selective supramolecular host-guest interaction between [4]CHBC and C70 was also investigated.

Electric field induced silicon carbide nanotubes: a promising gas sensor for detecting SO2

Finding an effective strategy for detecting SO2 gas is very important in order to solve the problem of pollution of SO2. Based on the first-principles density functional theory (DFT) calculations, we herein explore the possibility of using (5, 5) silicon carbide nanotubes (SiCNTs) with an external electric field (EF) as a potential gas sensor for SO2 detection. It is found that SO2 molecules can be chemisorbed to the Si?C bonds of SiCNTs and can generate a different charge distribution under the EF, resulting in the breaking of some S?C bonds. It is these broken S?C bonds that induce a decrease in the band gap. Furthermore, with the concentration of SO2 exceeding 20%, the band gap of SiCNT under an EF of 9.00?V?nm?1 would be reduced from 1.75?eV for SiCNT to zero, indicating the transformation from a semiconductor to a conductor. Hence, with an appropriate EF, SiCNTs can effectively respond to SO2 and serve as sensors for detecting SO2 gas.