The hydrogen–oxygen reaction on lanthanum oxide and europium oxide

Abstract

The stoichiometric hydrogen–oxygen reaction has been studied in a static system over lanthanum oxide and europium oxide at an initial hydrogen pressure of approximately 200 N m−2 from 480 to 775 K, and at different initial hydrogen pressures from 70 to 750 N m−2 over the same temperature range. Nonstoichiometric reactions were conducted at five different temperatures over lanthanum oxide and four different temperatures over europium oxide, at hydrogen–oxygen ratios in the range 0.1 to 10. After detailed kinetic analysis it is shown that the results fit an equation of the form:[Formula: see text]where k is a proportionality constant, [Formula: see text] and [Formula: see text] are the adsorption coefficients for hydrogen and oxygen, respectively, PT is the total pressure of hydrogen plus oxygen, [Formula: see text] and [Formula: see text] are the partial pressures of hydrogen and oxygen, respectively, and x equals 2 for lanthanum oxide and 1 for europium oxide. The mechanism involves the competitive adsorption of molecular hydrogen and oxygen, with the rate-determining step involving the interaction between adsorbed hydrogen molecules and adsorbed oxygen or hydrogen peroxide (double hydroxide groups).