Zhanjiang Normal University

About: Zhanjiang Normal University is a education organization based out in Zhanjiang, China. It is known for research contribution in the topics: Photocatalysis & Photoluminescence. The organization has 1768 authors who have published 1587 publications receiving 14933 citations.

Graphene-like MoS2/amorphous carbon composites with high capacity and excellent stability as anode materials for lithium ion batteries

Abstract: A facile process to synthesize graphene-like MoS2/amorphous carbon (a-C) composites was developed. MoS2/C composites were firstly prepared by hydrothermal method employing sodium molybdate, sulfocarbamide and glucose as starting materials. The graphene-like MoS2/a-C composites were obtained after annealing at 800 °C in H2/N2. The samples were characterized by XRD, SEM, EDS and HRTEM. It was confirmed that in the composites MoS2 has a structure of single-layer, which is named graphene-like nanostructure. The graphene-like MoS2 nanosheets were uniformly dispersed in amorphous carbon. The interlaminar distance of the adjacent graphene-like MoS2 nanosheets in the composites measured was ∼1.0 nm. The mechanism of the formation of the graphene-like MoS2/a-C composites was investigated. The graphene-like MoS2/a-C composites exhibited high capacity and excellent cyclic stability used as anode materials for Li-ion batteries. The composite prepared by adding 1.0 g of glucose in hydrothermal solution exhibited the highest reversible capacity (962 mAh g−1) and excellent cyclic stability. After 100 cycles, it still retained 912 mAh g−1. The significant improvements in the electrochemical properties of the graphene-like MoS2/a-C composites could be attributed to the graphene-like structure of the MoS2 nanosheets and the synergistic effects of graphene-like MoS2 and amorphous carbon.

A carbon nitride/TiO2 nanotube array heterojunction visible-light photocatalyst: synthesis, characterization, and photoelectrochemical properties

Abstract: A carbon nitride/TiO2 nanotube array (CN/TNT) heterojunction photocatalyst with visible-light response was prepared by a simple electrochemical method. The photocatalyst was characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The photoelectrochemical properties and photocatalytic activities of the obtained-samples were systematically tested under visible light irradiation. The activity of heterojunction photocatalyst CN/TNTs is higher than that of TNTs. The obviously increased performance of CN/TNTs is ascribed mainly to enhancement of electron–hole separations both at the interface and in the semiconductors.

P-V criticality of topological black holes in Lovelock-Born-Infeld gravity

Abstract: To understand the effect of third order Lovelock gravity, $$P$$ – $$V$$ criticality of topological AdS black holes in Lovelock–Born–Infeld gravity is investigated. The thermodynamics is further explored with some more extensions and in some more detail than the previous literature. A detailed analysis of the limit case $$\beta \rightarrow \infty $$ is performed for the seven-dimensional black holes. It is shown that, for the spherical topology, $$P$$ – $$V$$ criticality exists for both the uncharged and the charged cases. Our results demonstrate again that the charge is not the indispensable condition of $$P$$ – $$V$$ criticality. It may be attributed to the effect of higher derivative terms of the curvature because similar phenomenon was also found for Gauss–Bonnet black holes. For $$k=0$$ , there would be no $$P$$ – $$V$$ criticality. Interesting findings occur in the case $$k=-1$$ , in which positive solutions of critical points are found for both the uncharged and the charged cases. However, the $$P$$ – $$v$$ diagram is quite strange. To check whether these findings are physical, we give the analysis on the non-negative definiteness condition of the entropy. It is shown that, for any nontrivial value of $$\alpha $$ , the entropy is always positive for any specific volume $$v$$ . Since no $$P$$ – $$V$$ criticality exists for $$k=-1$$ in Einstein gravity and Gauss–Bonnet gravity, we can relate our findings with the peculiar property of third order Lovelock gravity. The entropy in third order Lovelock gravity consists of extra terms which are absent in the Gauss–Bonnet black holes, which makes the critical points satisfy the constraint of non-negative definiteness condition of the entropy. We also check the Gibbs free energy graph and “swallow tail” behavior can be observed. Moreover, the effect of nonlinear electrodynamics is also included in our research.

Electronic synergism of pyridinic- and graphitic-nitrogen on N-doped carbons for the oxygen reduction reaction

Abstract: Nitrogen-doped carbon materials (NCs) are extensively studied for the oxygen reduction reaction (ORR). However, the nature of active sites of pyridinic nitrogen (NP) or graphitic nitrogen (NG) on NCs is still under debate. Herein, we demonstrated that the ORR activity of NCs in alkaline media depended on the electronic synergism between NP and NG, rather than any single type of N. We measured the transferable electrons of NCs by absorption spectroscopy using 7′7′8′8-tetracyanoquinodimethane as an electron acceptor. The transferable electron amount of NCs is relevant to either NP or NG, leading to the [NP] : [NG] ratio as an electron transfer descriptor of NCs in a reverse volcano curve manner across nineteen NCs. The similar dependence of ORR activity on the [NP] : [NG] ratio of NCs was also discovered, demonstrating the synergistic effect of NP and NG. These results provide a new angle to understand the nature of ORR activity of NCs and optimize the ORR catalyst.