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Abstract A structural model of carbon nanocoils (CNCs) on the basis of carbon nanotubes (CNTs) was proposed. The Young’s moduli and spring constants of CNCs were computed and compared with those of CNTs. Upon elongation and compression, CNCs exhibit superelastic properties that are manifested by the nearly invariant average bond lengths and the large maximum elastic strain limit. Analysis of bond angle distributions shows that the three-dimensional spiral structures of CNCs mainly account for their unique superelasticity.

A predator-prey model with sparse effect and cross-diffusion under homogeneous Neumann boundary condition are discussed. Firstly 'by means of maximum principle and Harnack inequality ,the prior estimate to the positive solutions of the model is given. Secondly 'by using the integral property ,the non-existence of the non-constant positive solutions is considered. Finally ,the Leray-Schauder degree theory is utilized for discussing the existence of the non-constant positive solutions. [ABSTRACT FROM AUTHOR]

The pursuit of highly efficient electrocatalysts for the alkaline hydrogen evolution reaction (HER) is of paramount importance for water splitting. However, it is still a formidable task in Mo 2 C-based materials because of the agglomeration and strong Mo-H binding of Mo 2 C units. Herein, a novel CeOCl-CeO 2 /Mo 2 C heterostructure nesting within a three-dimensional porous nitrogen-doped carbon matrix has been designed and used for catalyzing HER via simultaneous morphology and heterointerface engineering. As expected, the optimal CeOCl-CeO 2 (0.2)/Mo 2 C@3DNC exhibits impressive HER activity, with a low overpotential of 156 mV at a current density of 10 mA cm -2 coupled with a slight Tafel slope of 62.20 mV dec -1 . Introducing a Ce promoter, that is CeOCl and CeO 2 , would endow the interface with an internal electric field and electron redistribution between CeOCl-CeO 2 and Mo 2 C induced by the heterogeneous work function difference. Moreover, experimental investigation and density functional calculations confirm that the CeOCl-CeO 2 /Mo 2 C heterointerface can downshift the d-band center of the active Mo center, weakening the strength of the Mo-H coupling. This proposed concept, engineering Ce-based promoters into active entities involved in the heterostructure to modulate intermediate adsorption, offers a great opportunity for the design of superior electrocatalysts for energy conversion.

The modulation of the electronic structure is the effective access to achieve highly active electrocatalysts for the hydrogen evolution reaction (HER). Transition-metal phosphide-based heterostructures are very promising in enhancing HER performance but the facile fabrication and an in-depth study of the catalytic mechanisms still remain a challenge. In this work, the catalytically inactive n-type CeO x is successfully combined with p-type CoP to form the CoP/CeO x heterojunction. The crystalline-amorphous CoP/CeO x heterojunction is fabricated by the phosphorization of predesigned Co(OH) 2 /CeO x via the as-developed reduction-hydrolysis strategy. The p-n CoP/CeO x heterojunction with a strong built-in potential of 1.38 V enables the regulation of the electronic structure of active CoP within the space-charge region to enhance its intrinsic activity and facilitate the electron transfer. The functional CeO x entity and the negatively charged CoP can promote the water dissociation and optimize H adsorption, synergistically boosting the electrocatalytic HER output. As expected, the heterostructured CoP/CeO x -20:1 with the optimal ratio of Co/Ce shows significantly improved HER activity and favorable kinetics (overpotential of 118 mV at a current density of 10 mA cm -2 and Tafel slope of 77.26 mV dec -1 ). The present study may provide new insight into the integration of crystalline and amorphous entities into the p-n heterojunction as a highly efficient electrocatalyst for energy storage and conversion.