Structure and reactivity of Ni-Au nanoparticle catalysts

We discuss the design of a Ni-Au nanoparticle catalyst system, which is bas ed on the detailed experimental and theoretical understanding of the alloyi ng and the chemical reaction processes on single-crystal surfaces. The allo y formation and structure of Ni-Au catalysts supported on SiO2 and on MgAl2 O4 are simulated by Monte Carlo schemes as well as experimentally studied b y a combination of in situ X-ray absorption fine structure, transmission el ectron microscopy, and in situ X-ray powder diffraction. On-line mass spect rometry is used to follow the reactivity of the catalyst and thermogravimet ric analysis provided information on the deposition rate of carbon during s team reforming of n-butane. The simulations and the experiments give eviden ce for the formation of a Ni-Au surface alloy on the Ni particles fur both supports. The Ni-Au catalysts exhibiting the surface alloy are active for s team reforming and are more resistant toward carbon formation than the pure Ni catalyst. Blocking of highly reactive Ni edge and kink sites by Au atom s is presumably the reason for the increased robustness of the Ni-Au cataly st.