Various techniques are employed to characterize the internal structures of catalyst materials. X-ray diffraction (XRD) can provide information on the crystalline structure, while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) offer insights into the morphology and size of particles. BET surface area analysis measures the specific surface area, and porosimetry determines pore size distribution. These techniques are essential for understanding the relationship between structure and function in catalysis.