Non-bonding modulations between single atomic cerium and monodispersed selenium sites towards efficient oxygen reduction

Currently,dual atomic catalysts(DACs)with neighboring active sites for oxygen reduction reaction(ORR)still meet lots of challenges in the synthesis,especially the construction of atomic pairs of elements from different blocks of the periodic table.Herein,a“rare earth(Ce)-metalloid(Se)”non-bonding heteronuclear diatomic electrocatalyst has been constructed for ORR by rational coordination and carbon support defect engineering.Encouraging,the optimized Ce-Se diatomic catalysts(Ce-Se DAs/NC)displayed a half-wave potential of 0.886 V vs.reversible hydrogen electrode(RHE)and excellent stability,which surpass those of separate Ce or Se single atoms and most single/dual atomic catalysts ever reported.In addition,a primary zinc-air battery constructed using Ce-Se DAs/NC delivers a higher peak power density(209.2 mW·cm^(−2))and specific capacity(786.4 mAh·gZn^(−1))than state-of-the-art noble metal catalysts Pt/C.Theoretical calculations reveal that the Ce-Se DAs/NC has improved the electroactivity of the Ce-N_(4)region due to the electron transfer towards the nearby Se specific activity(SA)sites.Meanwhile,the more electron-rich Se sites promote the adsorptions of key intermediates,which results in the optimal performances of ORR on Ce-Se DAs/NC.This work provides new perspectives on electronic structure modulations via non-bonded long-range coordination micro-environment engineering in DACs for efficient electrocatalysis.

Molecular mechanics on bonding and non-bonding interactions in (atom@C_(60))

The interactions between the embedded atom X (X=Li,Na,K,Rb,Cs; F,Cl,Br,I) and C60cage in the endohedral-form complexes (X@C60) are calculated and discussed according to molecular mechanics from the point of view of the bonding and non-bonding.It is found from the computational results that for atoms with radii larger than Li’s,their locations with the minimum interaction in (X@C60) are at the cage center,while atom Li has an off-center location with the minimum interaction deviation of-0.05 nm,and the cage-environment in C60 can be regarded as sphero-symmetry in the region with radius r of ~0.2 nm.It is shown that the interaction between X and C60 cage is of non-bonding characteristic,and this non-bonding interaction is not purely electrostatic.The repulsion and dispersion in non-bonding interactions should not be neglected,which make important contribution to the location with minimum interaction of X,at center or off center.Some rules about the variations of interactions with atomic radii have been

金属材料内部缺陷试块的热压扩散连接制备方法

针对空腔类缺陷的人工模拟无损检测试块的研制,提出热压扩散连接技术的制备方法。利用热压扩散连接方法,制备内部含有三种不同规格尺寸人工模拟缺陷的试块。分析结果表明,试块连接区域熔合较好,熔合线难以区分;基体组织未发生明显变化;试块内缺陷尺寸发生变化且呈现一定变化规律,变形率与缺陷边界夹角和缺陷所呈角度大小有关。试块宏观尺寸呈现一定的形变,无损检测及金相分析结果显示人工缺陷边界清晰,基体连接区域扩散连接充分且组织无有害缺陷。热压扩散连接法应用于空腔类缺陷的人工模拟无损检测试块的研制工作具有可行性。

Interaction between the alkali atoms and the C_(60) cage in the endohedral complexes (Alkali@C_(60))

At present, research interest in C60 is mainly focused on its complexes and its chemical modification and doping. Putting an atom （or a radical） or a molecule into another molecule to form a stable compound is a completely new novel field in chemistry. The quite large cavity in football-like C60 cage has put forward the possibility of trapping inside it an atom or a radical to form the endohedral complexes (X@C60). The alkali-containing complex (Alkali@C60) formed from C60 cage and alkali atoms is one kind of this endohedral complex. On these entirely new endohedral complexes, much valuable