Precise observation of growth of surface oxide layer for Pd and Cu nanoparticles during oxidative/reductive gases cyclic flow studied by real-time-resolved XAFS spectroscopy

Matsumura, Daiju   ; Nishihata, Yasuo; Okajima, Yuka*

We have demonstrated in situ and real-time-resolved X-ray absorption fine structure (XAFS) observation for oscillatory creation and removal reactions of surface oxide layer of Pd and Cu metal nanoparticles during cyclic flow of oxidative and reductive gases every 10 s. Pd and Cu -edges XAFS spectra were collected at about 1-2 Hz. Precise observation of edge position was utilized for monitoring surface oxidation and reduction reactions. Reaction rate of surface oxide layer creation by NO for Pd metal nanoparticle is faster in the case of H/NO cyclic ow than in CO/NO. Fast and two-step surface oxidation and reduction reactions were revealed in Cu metal nanoparticles.