X-RAY PHOTOELECTRON-SPECTROSCOPY AND DIFFRACTOMETRY OF MNOX CATALYSTS - SURFACE TO BULK COMPOSITION RELATIONSHIPS

Surface and bulk analyses of variously-composed, synthetic MnO(x) catalysts were carried out by means of X-ray photoelectron spectroscopy (XPS) and diffractometry (XRD), respectively. The data obtained were processed for a comprehensive assessment of bulk and surface compositions, surface oxidation state, and crystallite size. The XPS data processing revealed that a credible assessment of the surface composition (MnOx(OH)y(OH2)z necessitates: (i) the implementation of experimental sensitivity factors determined on a local reference surface maintaining a close chemical similarity to the test materials, and (ii) the fine evaluation of contributions of various oxygen-containing surface species to the O 1s electron emission. The most prominent result of the present investigation is that the exposure of the bulk composition at the surface is quite proportioned. Such a surface to bulk intimacy is thought to enable genesizing the surface composition appropriate for certain catalytic and selectivity, via a possible control over the bulk formation events [16].