摘要
镁氢化物的结构热力学稳定性高、释放氢动力学缓慢等延缓了其实用化进程,研究者通过向其掺杂适量的具有催化效应的合金元素或化合物来改善该问题。MgH_(2)氢化物释放氢难易程度与其反应焓变和活化能有关,其机制主要有:较大颗粒或大块材料中镁形核生长——MgH_(2)基体表面的氢原子扩散模型;微米或纳米级的Mg形核生长——新形成镁外层的氢原子扩散模型。掺杂金属元素(M、RE)或二元氧化物或卤化物的催化作用在于形成的(M或RE)-H削弱了Mg-H键的结合能力,在机械球磨的协助下,二元氧化物或卤化物促进MgH_(2)形成丰富的缺陷并增大其比表面积、诱导Mg表面改性、激发Mg-H解离等。掺杂三元或多元化合物的贡献在于改善复合材料的微观特性、降低释放氢的起始温度和释放氢反应的活化能、提高释放氢速率。掺杂化合物对MgH_(2)的催化机制主要为:调整了MgH_(2)释放氢的反应途径、增加释放氢的反应活性点、在MgH_(2)基体中分布均匀、具有独特的化学活性、与MgH_(2)反应原位形成的产物——金属单质、氧化物或氟化物或合金、氢化物等具有多相协同催化作用。本文归纳了改善MgH_(2)释放氢掺杂的三元或多元化合物的催化作用与机制,提出了改善MgH_(2)释放氢的热力学和动力学的研究措施并展望了其应用前景,以期为研制出使用条件温和、热力学/动力学条件不苛刻的MgH_(2)氢化物提供参考。
The high structural thermodynamic stability and slow kinetics of hydrogen release of magnesium hydride have slowed down its practicalization process,and researchers have improved the problem by doping it with appropriate amounts of alloying elements or compounds with catalytic effects.The difficulty of releasing hydrogen from MgH_(2)hydride is related to its reaction enthalpy change and activation energy.The main mechanisms are:Mg nucleation growth in larger particles or bulk materials—hydrogen atom diffusion model on the surface of MgH_(2)matrix;micron or nanoscale Mg nucleation growth—a hydrogen atom diffusion model for the newly formed magnesium outer layer.The catalytic effect of doping metal elements(M,RE)or binary oxides or halides is that the formed(M or RE)-H weakens the binding ability of Mg-H bonds.With the assistance of mechanical ball milling,the binary oxides or halides promote MgH_(2)to form abundant defects and larger specific surface area,induce Mg surface modification,stimulate Mg-H dissociation,etc.The contribution of doping ternary or multi-component compounds is to improve the microscopic properties of composite materials,reduce the initial temperature of hydrogen release and the activation energy of hydrogen release reaction,and increase the rate of hydrogen release;the main catalytic mechanism is that these compounds can adjust the hydrogen release reaction pathway of MgH_(2),increase the reactive sites for releasing hydrogen,uniform distribution in MgH_(2)matrix,unique chemical activity,products formed in situ by reaction with MgH_(2)—metal element,oxide or fluoride or alloy,hydride have multiphase synergy catalysis.This article summarizes the catalytic effects and mechanisms of hydrogen-doped ternary or multi-element compounds to improve the release of hydrogen from MgH_(2).The obstacles and mechanisms of hydrogen release from MgH_(2),the catalytic effects of metals and compounds,especially the catalytic effects and mechanisms of ternary or multi-element compounds,are introduced.In this paper,the catalytic action and mechanism of improving the ternary or multi-component compounds doped with hydrogen release from MgH_(2)are summarized,and research measures to improve the thermodynamics and kinetics of hydrogen released by MgH_(2)are put forward and look forward to its application prospects,hoping to provide a reference for the development of MgH_(2)hydrides with mild use conditions and less severe thermodynamic/kinetic conditions.
作者
董小平
张昭卿
杨丽颖
忻胜海
李健
DONG Xiaoping;ZHANG Zhaoqing;YANG Liying;XIN Shenghai;LI Jian(College of Quality and Technical Supervision,Hebei University,Baoding 071002,Hebei,China;Hebei New Energy Vehicle Power System Lightweight Technology Innovation Center(under preparation),Baoding 071002,Hebei,China;Baoding New Energy Vehicle Power Engineering Technology Research Center,Baoding 071002,Hebei,China)
出处
《材料导报》
CSCD
北大核心
2023年第17期28-35,共8页
Materials Reports
基金
河北省自然科学基金(E2021201032)
2023年河北省和河北大学校级大学生创新创业训练项目(S202310075044,2023232)
教育部“春晖计划”合作研究项目(202200397)
河北大学2022年实验室开放项目(sy202266)。
