Characterization of Model Nanocatalysts by X-ray Absorption Spectroscopy

Nanoparticles, due to their finite sizes, demonstrate enhanced catalytic properties compared with their bulk counterparts. In order to understand their mechanisms of work and design new and better nanocatalysts, fundamental understanding of the structural and electronic properties is required. Well-defined nanoclusters are most attractive for such purpose. Their unique shapes, compositional motifs, enhanced strain, electronic and structural heterogeneities, and their dynamic changes caused by the environment are all important descriptors of catalytic activity. The main challenge toward their systematic investigation is the scarcity of techniques that can characterize these attributes of structure with high spatial, energy, and temporal resolutions. In this chapter, we summarize a number of methods of extended X-ray absorption fine structure (EXAFS) spectroscopy recently developed for characterization of well-defined nanocatalysts. We demonstrate how EXAFS enables the determination of their structure, size, shape, and compositional motifs. We also describe challenges that impede accuracy of EXAFS methods and discuss corrective strategies.