Collaborative Research: Understanding the Materials Chemistry to Engage Anion Uptake and Release in Layered Transition Metal Oxides and Hydroxides

能够承载阴离子的层状过渡金属氧化物和氢氧化物材料具有许多与能源和环境相关的应用。然而，大多数金属氧化物和氢氧化物不能可逆地吸收和释放阴离子，限制了它们在各种设备中的可持续应用。在该项目中，由材料研究部固态与材料化学项目支持，研究团队旨在了解氯离子和硫酸盐阴离子如何在层状材料中移动，并开发层状过渡金属氧化物和氢氧化物材料库，用于可逆阴离子的吸收和释放。利用原子尺度模型和量子理论建立了层状氧化物的性质数据库，并获得了阴离子与层状材料之间原子相互作用的基本见解。理论和实验的紧密结合有助于确定负离子在寄主材料层间区域插入和提取的潜在机制，并建立材料局部结构、阴离子和水分子在氯离子和硫酸盐可逆寄存到层状金属氢氧化物中的基本作用。该项目加强了研究团队的教育和推广工作，通过一系列针对普通公众、高中学生和教师、本科生和研究生的活动，增加代表性不足群体的科学参与和参与。层状双氢氧化物（LDHs）具有二维带正电的纳米片和带负电的离子以及层间区域的结构水分子，在广泛的能源和环境相关应用中具有优势，包括多价阴离子电池、高容量海水淡化和离子修复。然而，对于局部结构及其与阴离子的原子相互作用如何影响LDHs中可逆阴离子的摄取和释放，缺乏基本的理解。该项目由材料研究部固态与材料化学项目支持，研究团队旨在了解过渡金属氧化物和氢氧化物层状材料中阴离子插入和提取过程中离子水合作用、原子输运、材料缺陷和电荷转移之间的相互作用。该团队提出合成Fe-和Co-基LDH， [M2+1-x(M/Ni)3+x(HO−)2]x+ [(An−)n/2·yH2O]x- (M: Fe, Co； A：插入阴离子基团如Cl-和SO42-)，其中Ni3+掺杂固定了层间结构水并稳定了层间结构。该团队计划在原子建模的指导下，优化LDH的局部结构（例如，无序和位点缺陷）和远程结构（例如，层间距离，晶相），以协助阴离子的摄取和释放。该团队计划使用中子/ x射线全散射和对分布函数分析以及x射线吸收光谱来研究LDHs的金属-氧（M-O）八面体如何与阴离子、水和阳离子相互作用。密度泛函数理论计算，先进的采样和分子动力学模拟被用来获得原子尺度的见解之间的相互作用的M-O八面体在提出的LDHs，阴离子和水，为实验调整LDHs的界面结构提供指导。实验和建模工作之间的交织性质通过实验和模拟相互通知，提供了更好地解决结构细节。通过本科生研究人员交流项目、高中学生和教师的实践活动以及本科生和研究生的高级研究培训经验，教育和推广工作促进了团队的目标，即增加代表性不足群体学生的参与。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical SummaryLayered transition metal oxide and hydroxide materials capable of hosting anions could have many energy- and environment-related applications. However, most metal oxides and hydroxides cannot reversibly uptake and release anions, limiting their sustainable applications in various devices. In this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, the research team aims to understand how chloride and sulfate anions move in the layered materials and develop a library of layered transition metal oxide and hydroxide materials for reversible anion uptake and release. Atomic-scale modeling and quantum theory are used to build a property database of layered oxides, and gain fundamental insights into atomic interactions between anion and layered materials. The close integration of theory and experiment helps determine the underlying mechanisms of the anion insertion and extraction in the interlayer region of the host materials and to establish the fundamental roles of material local structures, anion, and water molecules for reversible hosting of chloride and sulfate into layered metal hydroxides. This project enhances education and outreach efforts by the research team to increase scientific engagement and participation from underrepresented groups through a range of activities aimed at the general public, high school students and teachers, undergraduate students, and graduate students.Technical SummaryLayered double hydroxides (LDHs) have two-dimensional positively charged nanosheets and host negatively charged ions and structural water molecules in the interlayer regions, offering advantages in a wide range of energy- and environment-related applications, including multivalent anion batteries, high-capacity desalination, and ion remediation. However, there is a lack of fundamental understanding of how the local structure and their atomic interaction with anions affect the reversible anion uptake and release in LDHs. In this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, the research team aims to understand the interplay between ion-hydration, atomic transport, material defect, and charge transfer on anion insertion and extraction in transition metal oxide and hydroxide layered materials. The team proposes to synthesize Fe- and Co-based LDH, [M2+1-x(M/Ni)3+x(HO−)2]x+ [(An−)n/2 · yH2O]x- (M: Fe, Co; A: inserted anion groups such as Cl- and SO42-,), where Ni3+-doping immobilizes the structural water in the interlayers and stabilizes the interlayer structure. The team plans to optimize LDH local structures (e.g., disorder and site defect) and long-range structure (e.g., interlayer distance, crystalline phase), guided by atomic modeling, to assist the anion uptake and release. The team plans to use neutron/X-ray total scattering and pair distribution function analysis and X-ray absorption spectroscopy to study how metal-oxygen (M-O) octahedra of LDHs interact with anions, water, and cation. The density functional theory calculations, advanced sampling, and molecular dynamics simulations are used to gain atomic-scale insights into interactions between M-O octahedra in the proposed LDHs, anions, and water, providing guidelines for experimentally tuning the interfacial structuring of the LDHs. The interwoven nature between the experimental and modeling efforts provides better-resolved structural details via experiments and simulations informing each other. The education and outreach efforts advance the team's goals to increase participation of students from underrepresented groups via an undergraduate researcher exchange program, hands-on activities for high school students and teachers, and advanced research training experiences for undergraduate and graduate students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.