| Metallic glass（MG）with long-range disordered atomic arrangement usually possesses a unique combination of physical and chemical properties.However,it is great difficult to investigate the correlation between the structure and properties of MGs due to their disordered characteristics.Recent studies have shown that the characteristics of metastable energy of MGs can bridge the structure and properties,which is expected to achieve the tuning of the physical and chemical properties.The pursuit of high-energy MG is expected to improve its plasticity,friction resistance,catalytic performance,etc.,leading the widely concerned by researchers.In addition,high-energy MGs have more significant structural inhomogeneity and complex relaxation behaviors theoretically.Therefore,exploring the dynamics of high-energy MGs is of great significance for understanding the nature of glassy states and recognizing scientific problems in condensed matter physics.To solve these problems,we developed two kinds of high-energy MGs,nano-structure metallic glass（NG）and metallic glassy wire（MGW）.The structural and dynamic heterogeneity of high-energy MGs were systematically studied by relaxation behavior,and the correlation between energy state and catalytic performance of MGs was established.Furthermore,the feasibility of industrial application of high-energy NG in direct urea fuel cells（DUFC）was verified for the first time.The main investigations are as follows:（1）Ni-P NG was prepared by pulsed electrodeposition.The unique microstructure and energy state of Ni-P NG were systematically characterized.The method of stress relaxation was applied to investigate the structure and dynamic heterogeneity of NG,and the mechanical property of Ni-P NG was studied by combining the stress relaxation behavior with the structural characteristics.The results directly proved that Ni-P NG possesses the higher energy state,and the structural and dynamic inhomogeneity of Ni-P NG are stronger than that of conventional MG.During the stress relaxation,Ni-P NG exhibited larger value of n,higher volume fraction of liquid-like region,and faster relaxation kinetic process.Moreover,an anomalous peak is observed in the activation energy spectra of NG at 435 K,which may relate to a hidden poly-amorphous phase transition in Ni-P NGs.Furthermore,the mechanical property of Ni-P NG was also investigated by combining the structural characteristics.It is found that Ni-P NG has obvious room temperature tensile plasticity and lower tensile strength than that of MG with the identical composition,and the strain of tensile deformation is up to 10.67%on room temperature.（2）Various MGWs were prepared by the method of Taylor–Ulitovsky.The relaxation behavior of MGW has been studied systematically by dynamic modulus spectrum（DMS）,and a newα’relaxation mode betweenαrelaxation andβrelaxation has been discovered.Moreover,the excitation ofα’relaxation can only appear in an intermediated range of energy state,which is related to the surface topology around the potential energy landscape（PEL）energy state.Correspondingly,the effective cooling rate for exciting theα’relaxation is estimated to be about107-108 K/s.In addition,α’relaxation is found to be a universal relaxation mode,which is not only found in MGWs,but also in some rejuvenated MG bulks（or ribbons）and NGs with high energy state.Finally,it is shown that the activation ofα’relaxation can significantly affects the mechanical behavior of metallic glass at high temperature and can notably improve the homogeneous tensile deformability of metallic glasses.（3）The relationship between microstructure,energy state and catalytic performance of Ni-P NG prepared by pulsed electrodeposition was systematically studied.In this study,the high energy state of NG（including volume energy and surface energy）is attributed to its unique heterogeneous microstructure,which significantly improves the catalytic performance of NG,including urea oxidation reaction（UOR）,oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）.Specifically,modified Ni-P NG require potential of mere 1.360 V at a current density of 10 m A cm-2,with a Tafel slope of 13 m V dec-1,which is the best UOR performance in Ni-based alloys.This work demonstrates that the nanostructurization of MGs provides a universal and effective pathway to upgrade the energy state of MGs for the design of high-performance catalysts in energy conversion.（4）A low-cost and high-performance hierarchical porous NG（HPNG）electrode was developed for direct urea fuel cells（DUFC）,and the application of high-energy NG in DUFC was realized for the first time.The industrial-scale production of Ni-P HPNG electrodes demonstrated one of the best performances reported so far on UOR,achieving a potential of1.33 V at the current density（j）of 10 m A cm-2,as well as the Tafel slope of 9.77 m V dec-1.A DUFC was designed using a membrane electrode assembly（MEA）system with HPNG-40 as anode electrode material.Furthermore,a DUFC system with Ni-P HPNG anode electrode shows a performance breakthrough as indicated the open-circuit voltage（OCV）of 0.89 V,the maximum power density of 38.15 m W cm-2 and the maximum current density of 254 m A cm-2for 0.5 M urea.Meanwhile,this DUFC system achieves a urea degradation efficiency as high as～50%within 30 min,achieving an organic combination of high pollution reduction and high productivity. |
