高熵合金结构与储氢性能的中子衍射和理论研究

High entropy alloy (HEA) is demonstrated to be very promising for hydrogen energy storage; however, the research is still in its infancy stage, i.e. some fundamental questions remain unclear and hydrogen storage efficiency needs to be improved. This project aims to study HEA for hydrogen storage application from both theoretical and experimental points of view. Combined in-situ neutron diffraction and computational materials simulation will be used to solve the critical question of hydrogen occupancy and its structural evolution. A density functional theory (DFT) method based on quantum mechanics will be used to gain deeper understanding of the interaction between hydrogen atom and HEA elements as well as the underlying physical mechanism. Through theoretical HEA element design and high-performance DFT calculation, new types of high efficiency hydrogen storage HEA candidates will be predicted. Then experiments will be carried out to synthesize these HEAs to study the structure and understand the effects of element and lattice distortion on the hydrogen storage properties. Theoretical and experimental studies will be combined for further materials screening to identify the most suitable elements of HEA and improve the hydrogen storage efficiency. We propose in this project to examine the hydrogen occupancy by combined in-situ neutron diffraction and DFT calculations. The results will be illuminating to reveal the hydrogen storage mechanism of HEA and identify effective strategy towards enhancing hydrogen storage performance of HEA, thus providing important guidance for application of hydrogen energy.

高熵合金是一种极具潜力的储氢能源材料，但相关研究处于起步阶段，有许多科学问题不明确，影响了储氢性能的提升。本课题拟对高熵合金储氢应用相关的科学问题进行理论和实验研究。针对氢原子占位不明确这一关键问题，结合中国工程物理研究院先进原位中子衍射平台和计算材料学模拟，确定其结构信息并揭示其演变规律。采用基于量子力学的密度泛函理论从原子层次理解氢与高熵合金元素相互作用的物理机制，填补理论研究空白。通过高性能计算和成分设计，理论预测性能优异的新型储氢高熵合金，并结合实验研究其结构与性能，总结合金元素和晶格畸变对储氢性能的影响规律。进一步结合理论和实验进行筛选，寻找最佳成分配比，以实现高熵合金储氢性能的提升。本项目结合密度泛函理论和原位中子衍射方法研究高熵合金的储氢性能，其研究结果将有利于揭示高熵合金材料的储氢机制，获得性能良好的储氢体系以及提高储氢量的一般性规律，对氢能应用有重要的参考价值和指导意义。

高熵合金是一种极具潜力的储氢能源材料，但相关研究处于起步阶段，有许多科学问题不明确，影响了储氢性能的提升。本课题结合第一性计算模拟和中子衍射实验研究，探索了氢元素在一系列高熵合金体系中的实际占据位置及其演变规律以及氢与高熵合金元素相互作用的物理机制，并通过成分设计、组分优化以及掺杂调控提出了提升高熵合金储氢能力的具体方法，获得了具有高储氢量、低热稳定性的储氢高熵合金模型。研究发现，BCC相高熵合金氢化物中，氢倾向于占据八面体间隙位置；而在FCC相高熵合金氢化物中，氢更倾向于占据四面体间隙位置；高熵合金在吸氢后会发生结构相变，这种相变来源于氢与氢之间的排斥作用随氢浓度的增加而增强；氢在脱附过程中以原子形式脱附；适量的贵金属掺杂可提升高熵合金的储氢量。本研究提出具有高储氢量、低热稳定性的储氢高熵合金模型为：质量较小、同时包含氢亲和金属元素和非氢亲和金属元素、金属组分具有较高的电负性、金属元素的原子尺寸较小、体系的化学无序度较高、含有少量的贵金属元素的高熵合金。本项目的研究结果揭示了高熵合金材料的储氢机制，获得了性能良好的储氢体系以及提高储氢量的一般性规律，这对氢能的应用有重要的参考价值和指导意义。