  I present here the results of the first principles studies of the adsorption
energetics of the intermediates of the oxygen electro-reduction reaction (ORR)
on the Se modified Ru(0001) surface. The calculations were performed for the
1/3 ML and 1/6 ML coverage of Se, as well as for the clean Ru(0001) as a
reference. The binding energies of O and OH on Ru(0001) are found to decrease
significantly upon the presence of the Se and this effect to be increasing with
the Se coverage. The Se surface modification is found not to change Ru LDOS
noticeably. However, Se atoms accept electronic charge from the surface and
thus become negatively charged. As a result, they repeal electrostatically the
adsorbed negatively charged O and OH intermediates, and this way reduce their
binding energies. This effect provide an alternative way of tuning reactivity
of the catalyst surfaces. Since for the Ru case, reduction of the O and OH
binding energies makes ORR energetically favorable, Se modification
dramatically improve the ORR rate on Ru. Adsorption of O2 and co-adsorption of
the ORR intermediates and water have also been studied. The effect of the
co-adsorption on the binding energies of O and OH are discussed.
