Synchrotron X-ray diffraction studies of inorganic materials and heterogeneous catalysts

Abstract

The special features of synchrotron X-radiation and the types of instrumentation required for a range of synchrotron X-ray diffraction experiments are outlined. A diverse range of applications to inorganic and heterogeneous catalyst systems are discussed. Grazing incidence X-ray diffraction experiments have revealed a number of surface structures and followed surface phase transformations; similar studies of boundary and interfacial structures are cited. Experiments on catalytic metals dispersed on supports have exploited anomalous scattering effects. High-resolution powder diffraction has assisted phase identifications, provided quantitative data on peak broadening (such as arise from particle size effects or stacking disorder), enabled studies of subtle superstructures and a growing number of ab initio structure solutions, and permitted Rietveld refinements of a range of inorganic materials. The potential for performing measurements on individual crystallites in the micrometre size regime has been demonstrated; a small number of successful single-crystal structure refinements have been described. Single-crystal Laue methods have been also applied successfully to structure refinements and solutions; this configuration potentially permits data sufficient for structure definition to be recorded on a nano-microsecond time scale. A range of studies that are time-resolved (currently on somewhat longer scales), and various studies under non-ambient conditions (such as at high or low temperatures, at extreme pressures, or under applied magnetic and electric fields) have also been described. These various applications of synchrotron X-ray diffraction techniques to inorganic and heterogeneous catalyst systems both illustrate already substantial contributions to our understanding, and promise still greater advances from future applications.