It is shown experimentally that the electric charge of unsupported catalyst particles has a major influence on the methanation of CO with nanosized Ni particles as catalyst at temperatures between 680K and 720K. Neutral particles showed an apparent activation energy of 148kJ/mol, significantly higher than the apparent activation energies of 43kJ/mol and 60kJ/mol for negatively and positively charged particles, respectively. The obtained activation energies are comparable to energies obtained for different sites on alumina supported nickel catalysts. The change in activation energy can be qualitatively explained by different electron interchange between the chemisorbed species and the catalyst. We suggest that the observed effect of electron enhancement or depletion on catalysis is also a governing effect in strong metal support interaction (SMSI), where the displacement of electrons is related to the contact potential between catalyst and substrate.
Charge dependent catalytic activity of gasborne nanoparticles
C. Peineke, P. Davoodi, M. Seipenbusch, A. Weber, A. Schmidt-Ott
J. Nanosc. Nanotechnol., accepted for publication 2010