X-Ray Photoelectron Spectroscopy (XPS) is a surface-sensitive analytical technique used to determine the elemental composition and chemical state of materials. It works by irradiating a sample with X-rays, which causes the emission of photoelectrons. By measuring the kinetic energy of these emitted electrons, researchers can identify the elements present and their chemical states. XPS is particularly useful in fields like materials science, chemistry, and nanotechnology. It provides valuable information about the surface properties of solids, including thin films and coatings, making it essential for studying catalysts, semiconductors, and other advanced materials.