Preparation of phosphorus-doped carbon nanospheres and their electrocatalytic performance for O_2 reduction

Phosphorus-doped carbon nanospheres without any metal residues were synthesized and characterized. The results revealed that the doping phosphorus atoms could significantly improve the electrocatalytic activity of graphitic carbon for the oxygen-reduction reaction （ORR） both in acidic and alkaline media, and the materials exhibited high electrocatalytic activity, long-term stability, and excellent tolerance to crossover effects especially in alkaline media. Quantum mechanics calculations with the density functional theory demonstrated that the changes in charge density and energetic characteristics of frontier orbitals for the P-doped graphene sheet could facilitate the ORR.

Dynamic carbon surface chemistry: Revealing the role of carbon in electrolytic water oxidation

Carbon materials have been widely used as electrodes, but the mechanistic roles are still not clear due to the complexity of the carbon surface chemistry. Herein we clarify that intrinsic material properties of carbon have to be activated by extrinsic factors. Pure carbon has no catalytic activity when used as electrode for electrocatalytic water oxidation. The evolution of oxygen functional groups on the carbon surface with increasing potential and the subsequent formation of real active sites with iron impurities from the electrolyte have been confirmed. These in-situ formed active sites protect the carbon from deep oxidation. This unprecedented finding not only provides insight into the dynamic evolution of carbon electrode surface chemistry and raises awareness of the need for detailed surface analysis under operando conditions, but also suggests a direction for the development of scalable and high-performance carbonbased electrode systems for various electrochemical applications.

Catalytic effect of alkali carbonates on CO_2 gasification of Pingshuo coal

Na2CO3, Li2CO3, and K2CO3 were used as additives to Pingshuo （PS） coal that was subsequently gasified under a CO2 stream. The catalytic gasification of coal samples by CO2 in the presence single or mixed alkali carbonates was investigated by thermogravimetric analysis. The experimental results indicate that the catalytic effect of Li2CO3 is significantly larger than that of Na2CO3 or K2CO3. The catalytic effect of the mixed, bi-metal carbonate containing Li2C03 and Na2C03, or Li2CO3, and K2C03, is related to the compo- sition of the catalyst and the proportion of the two components. The bi-metal carbonates having a mole ratio of 9：1 （lri：x） has the largest catalytic effect for PS coal gasification. A synergistic effect between Li and K, or Na, carbonate appears at temperatures greater than 1300 K. An un-reacted shrinking core model is suitable for kinetic analysis of catalytic gasification of coal samples in the presence of alkali carbonates. It is inappropriate, however, to evaluate the catalytic effect only by the activation energy obtained from the kinetic calculations.

Endoplasmic-reticulum-like catalyst coating on separator to enhance polysulfides conversion for lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries with high theoretical specific energy of 2600 Wh kg^(-1) are one of promising candidates for next-generation energy storage devices.However,the severe shuttle effect of intermediate polysulfides leads to rapid capacity decay during battery cycling,especially at high sulfur loading and high current density.Herein,the MnO nanoparticles covered carbon with endoplasmic-reticulum-like structure(MnO@ERC)as separator coating for Li-S batteries is proposed.The MnO@ERC coating can act as upper current collector to enhance electrical conductivity of cathode and decrease the interface impedance of the whole battery.More importantly,both the polar MnO nanoparticles and Mn_(3)O_(4) formed at the end of the charging process can catalyze the conversion of lithium polysulfides,which is convinced by the high adsorption energy and the elongate S–S bond.As a result,Li-S batteries based on MnO@ERC coating separator showed stable cycle for 350 cycles under 0.5C,high discharge specific capacity of 783.6m Ah g^(-1) after 100 cycles at 0.2 C,534.7 m Ah g^(-1) after 100 cycles under the sulfur loading of 5.26 mg cm;and low self-discharge rate of 9.1%after resting 48 h..

Novel hydrazine-bridged covalent triazine polymer for CO_2 capture and catalytic conversion

Carbon dioxide（CO_2） capture and catalytic conversion has become an attractive and challenging strategy for CO_2 utilization since it is an abundant, inexpensive, and renewable C1 resource and a main greenhouse gas. Herein, a novel hydrazine-bridged covalent triazine polymer（HB-CTP） was first designed and synthesized through simple polymerization of cyanuric chloride with 2,4,6-trihydrazinyl-1,3,5-triazine. The resultant HB-CTP exhibited good CO_2 capture capacity（8.2 wt%, 0 °C, and 0.1 MPa） as well as satisfactory recyclability after five consecutive adsorption-desorption cycles. Such a polymer was subsequently employed as a metal-free heterogeneous catalyst for the cyclo-addition of CO_2 with various epoxides under mild and solvent-free conditions,affording cyclic carbonates with good to excellent yields（67%–99%） and high functional-group tolerance. The incorporation of hydrazine linkages into HB-CTP＇s architecture was suggested to play the key role in activating epoxides through hydrogen bonding. Moreover, HB-CTP can be reused at least five times without significant loss of its catalytic activity.

Cesium carbonate supported on hydroxyapatite coated Ni_(0.5)Zn_(0.5)Fe_2O_4 magnetic nanoparticles as an efficient and green catalyst for the synthesis of pyrano[2,3-c]pyrazoles

Cesium carbonate supported on hydroxyapatite coated Nio.sZno.sFe2O4 magnetic nanoparticles （Nio.sZno.sFe2O4@Hap-Cs2CO3） was found to be magnetically separable, highly efficient, green and recyclable heterogeneous catalyst. The synthesized nanocatalyst has been characterized with several methods （FT-IR, SEM, TEM, XRD and XRF） and these analyzes confirmed which the cesium carbonate is well supported to catalyst surface. After full characterization, its catalytic activity was investigated in the synthesis of pyranopyrazole derivatives and the reactions were carried out at room temperature in 50：50 water/ethanol with excellent yields （88-95%）. More importantly, the Nio.5Zno.sFe204@Hap-Cs2CO3 was easily separated from the reaction mixture by external magnetic field and efficiently reused at least six runs without any loss of its catalytic activity. Thus, the developed nanomagnetic base catalyst is potentially useful for the green and economic production of organic compounds.

N-methylation of quinolines with CO2 and H2 catalyzed by Ru-triphos complexes

N-methyl-tetrahydroquinolines(MTHQs) are a kind of very useful chemicals, which can be obtained from N-methylation of amines.However, the methylation of quinolines which is a kind of highly unsaturated nitrogen-containing heterocyclic aromatic compounds has not been reported. In this work, we report the first work for the synthesis of MTHQs by methylation of quinolines using CO_2 and H_2. It was found that Ru(acac)_3-triphos [triphos: 1,1,1-tris(diphenylphosphinomethyl)ethanl] complex was very active and selective for the N-methylation reaction of quinolines, and the yield of the desired product could reach 99%.

Ruthenium-promoted reductive transformation of CO2

The reductive transformation of CO_2 to energy related products including formic acid, CO, formamide, methanol and methylamine could be a promising option to supply renewable energy. In this aspect, ruthenium has found wide application in hydrogenation of various carbonyl groups, and has successfully been applied to reductive transformation of CO_2 with high catalytic efficiency and excellent selectivity. In addition, ruthenium complexes have also served as effective photosensitizers for CO_2 photoreduction.Classified by reductive products, this review summarizes and updates advances in the Ru-catalyzed reduction of CO_2 along with catalyst development on the basis of mechanistic understanding at a molecular level.