Heterogeneous electrocatalysts with well-defined surface and catalytic site structures for clean energy and fuel conversions

Rational design and synthesis of efficient catalysts are paramount to the development of electrochemical devices for clean energy and fuel conversion. Heterogeneous electrocatalytic materials are promising for the easy integration of electrochemical devices; however, the structural complexity of heterogeneous electrocatalysts makes it a great challenge to elucidate the surface catalytic sites and the reaction mechanisms. This dissertation is centered on the chemical synthesis of heterogeneous electrocatalysts with well-defined catalytic site and surface structures that enables the fundamental understanding of structure-property relationship for the design and production of improved electrocatalysts.
Two chemical approaches to synthesizing well-defined heterogeneous electrocatalysts are covered in this dissertation. First, solution-based colloidal synthesis of nanocrystals provides an effective strategy to achieve atomically precise control of nanocrystal surfaces and interfaces as well as uniform sizes, shapes and compositions. The well-defined nanocrystals can be used as model catalysts with minimized structural complexity, leading to accurate qualitative and quantitative analyses of surface catalytic sites. Second, well-defined molecular catalysts are heterogenized and immobilized onto conductive carbon supports, which allows for the modulation of catalytic site coordination structure for the enhanced electrocatalysis.
This dissertation begins with an overview of heterogeneous electrocatalysis for clean energy electrochemical devices, including water electrolyzers and proton exchange membrane fuel cells (Chapters 1). The solution-based colloidal synthesis of well-defined nanocrystals is then summarized in Chapter 2. Based on this synthetic strategy, a series of core/shell and single-site nanocrystals are created for a variety of important electrocatalytic reactions, including the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) for water electrolyzers and the oxygen reduction reaction (ORR) for proton exchange membrane fuel cells, which is highlighted in Chapters 3-7. The immobilization of Co and Ir molecular catalysts onto conductive carbon supports using novel non-covalent strategies is reported in Chapters 8 and 9, which allows the heterogenization of molecular catalysts for the OER.