Reactivities of H2, O2 and H2O with the Cr surface between 77Â K and 298Â K

The quantitative reactivities of H2, O2 and H2O on the polycrystalline Cr surface prepared under ultra high vacuum condition were measured volumetrically as a function of the amount of reacted gas at pressures ranging from 10−8 Pa to 10−2 Pa and at 298 K. For the Cr-H2 system, the reactivity was measured also at 77 K. The Cr with a clean surface exhibited higher reactivity with H2 than those of Ni or Co at 298 K. Quantitative kinetic data of reactivities of H2, O2 and H2O with the Cr surface are reported, and mechanisms of the H adsorption on the Cr surface in H2, O2, and H2O exposures are discussed.