Holey Graphene-Supported Single Metal Atoms as Highly Efficient Electrocatalysts

点击翻译按钮获取中文摘要

Electricity can provide the needed energy for chemical reactions such as the splitting of water into hydrogen and oxygen. Electrocatalysts are materials that are often needed for efficient and cost-effective electricity-driven, chemical reactions. Single atom catalysts (SACs) are composed of single, isolated metal atoms held on solid base (support). Supported electrocatalysts have potentially high reaction speeds, and tunable behavior, high durability, and recyclability. However, SACs are usually produced using high temperature processes that lead to complex and difficult to characterize structures. In this project, Dr. Xiangfeng Duan and his team at University of California, Los Angeles are developing a general approach for the preparation of single metal atoms supported on graphine with well-defined and systematically-tunable structures. The team uses advanced X-ray analyses and electron microscopy imaging approaches to unambiguously identify the arrangement of the single metal atoms, and matches the structures with reactivities to determine the best catalysts. The goal of this research is to define design criteria for the next generation of highly efficient electrocatalysts that could be used in mobile electronics, transportation, and renewable energy. SACs can combine the merits of both homogeneous catalysts (e.g., highly uniform active sites, tunable coordination environment and maximized atom utilization efficiency) and traditional heterogeneous catalysts (e.g., high durability, easy separation from the product, excellent recyclability, and easy integration with electrodes for electrocatalysis). In this project, Dr. Xiangfeng Duan is developing a general approach to prepare a series of single metal atoms embedded in two-dimensional graphene lattices with well-defined atomistic structure and systematically tunable metal centers (e.g., Fe, Co, Ni, Cu, Ru, Pd, Pt), then evaluating their catalytic properties towards various electrochemical processes. The team uses extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) analyses as well as high resolution transmission electron microscopy imaging approaches to unambiguously identify the local coordination configuration of the single metal atoms. These are further correlated with electrocatalytic activities through both experimental and theoretical studies to establish the structure-property relationship. The general synthesis of a series of single metal sites supported by highly crystalline graphene can allow unambiguous structural identification and systematic catalytic investigations (both experimentally and theoretically). The goal is to establish structure-property correlation and thus define the critical steps toward the rational design of SACs with tailored activity, selectivity and stability.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.