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

Hydrogen production from methane in a dielectric barrier discharge using oxide zinc and chromium as catalyst

“…5). Although it is still ambiguous, the existence of Cr on the surface of catalyst seemed able to affect the kinetics of the H 2 reaction (Kato et al, 2006). This finding also mentioned that Cr could adsorb more hydrogen atoms than Co and Ni and possibly perform H 2 formation on the surface of the catalyst.…”

Effects of O2 and H2O preadsorptions on the H2 reactivity with the Cr surface

“…Owing to the endothermic reaction for the Cr-H system, the reaction process is expected to take place only in the surface region. Further details of the reaction kinetics of a gas (H 2 , O 2 , H 2 O) with the clean surface of Cr were reported in the previous paper [2]. In the present study, in order to examine the poisoning effects of O 2 and H 2 O preadsorptions on the H 2 reactivity, the clean surface of Cr was intentionally contaminated by exposing to O 2 or H 2 O gases with the amounts of 5 and 14 ML for each gas before H 2 exposure (shown in Fig.…”

“…Fig. 1 shows the reactivity of a gas (H 2 , O 2 , H 2 O) with the clean surface of Cr as a function of the amount of gas molecules reacted N gas at 298 K, and also, the reactivity of H atoms dissociated from H 2 O molecules is shown, which was calculated from the partial pressure of H 2 molecules desorbed in H 2 O adsorption [2]. At the initial stage, the reactivities of H 2 , O 2 and H 2 O with the clean surface of Cr were measured as the highest reaction probability r gas = 1.…”

“…Our previous study was made to clarify the kinetic properties of a clean Cr surface on the reactivities of H 2 , O 2 , and H 2 O gases under UHV condition at 298 K and also for H 2 at 77 K. As well, the reactivity of H atoms dissociated from H 2 O molecules was measured in comparison with that of H 2 molecules at 298 K. We reported that the Cr surface exhibits a much higher reactivity with H 2 compared to Ni and Co surfaces, and that the uptake of H atoms in H 2 O adsorption on the Cr surface is higher than in the adsorption of H 2 molecules as a result of the formation of the hydroxide layers [2]. In the present study, we aimed to investigate quantitatively the effects of O 2 and H 2 O preadsorption layers on the H 2 reactivity with the Cr surface by using the same UHV technique.…”

“…In our group, the surface features of Ti-Cr based alloys and its compositional element Cr have been focused on [1,2]. Cr is an interesting element because of its high oxidation states and catalytic properties.…”