Low-temperature ortho-para conversion of hydrogen on silver

Abstract

A study of the low temperature ortho-para conversion of hydrogen on sintered silver particles was carried out to probe the surface for paramagnetic chemisorbed species. No paramagnetic structure of chemisorbed oxygen was found. Hydrogen chemisorbs on silver below room temperature only in the presence of adsorbed oxygen. No paramagnetic surface structure results. On the other hand, hydrogen chemisorbed at high temperatures gives a strongly paramagnetic surface; it appears to be chemisorbed in atomic form at centres containing firmly bound residual oxygen atoms and is not easily removed. This may explain the reported existence of a strongly bound paramagnetic form of oxygen and generally must be considered in adsorption studies on “bare” surfaces produced by hydrogen reduction.