Support Materials and Anion Composition as Stimuli for Understanding the Structures, Properties, and Behavior of Electrocatalysts
Abstract (summary)
The ability of water electrolysis and fuel cell technologies to replace existing fossil fuel infrastructure for energy generation and storage is currently hindered by their limited economic viability. To make water electrolysis and fuel cells more viable, we need to develop improved catalyst materials with high activity and durability while minimizing their cost. Such improvements require a deepened understanding of the relationships between catalyst structure, materials properties, and electrocatalytic behavior. In this work, we progress toward this goal by leveraging catalyst support materials and anion composition as vehicles for elucidating these relationships.
We begin by laying the foundation for the succeeding chapters, elaborating on the motivations, electrochemical reactions, scientific approaches, and experimental techniques we employ. We then examine the relationships between the support material, electronic structure, and anion composition of state-of-the-art water oxidation catalyst SrIrO3. By depositing thin films of SrIrO3 on single crystal substrates with varying lattice parameters, we impose various strain states on the material, which we then relate to changes to its electronic states and the favorability of oxygen vacancy formation using in situ and ex situ X-ray diffraction and absorption methods. We later take the reverse approach; instead of altering crystal structure to study anion composition, we investigate the effects of nonuniform anion composition on the crystal structure of novel perovskite oxynitride CaW(O,N)3. Through co-refinement of x-ray and neutron diffraction data, we shed light on the effectiveness of different methods for modelling anion arrangements in heteroanionic materials.
Building upon the discovery of an oxynitride, we demonstrate the applicability of oxynitrides as hydrogen evolution electrocatalysts, where we employ potentiostatic and potentiodynamic measurement techniques to demonstrate the activation of γ-Mo1−ε(NxOy)Hz at reducing potentials. We subsequently combine the “modification of support materials” approach with electrochemical analysis as we consider the impact of graphene support materials on the electrochemical behavior of commercial Pt/C for the oxygen reduction reaction. The use of both idealized and application-minded experimental setups allows us to begin to apply our new fundamental understandings toward practical and tangible impacts. Finally, we summarize our most significant results and provide potential directions for future research in these fields.
Indexing (details)
Chemistry;
Engineering
0537: Engineering
0485: Chemistry
