Surface modified metal hydride alloys for carbon dioxide reduction into hydrocarbons

Abstract

Metal alloys are one of few materials that are capable of acting as catalyst precursors in Sabatier reactions, reducing poisonous CO2 gas into different useful hydrocarbons. However, optimal reduction of CO2 through these materials takes place at relatively elevated temperatures due to poisoning-intolerance and deterioration of hydrogen absorption/desorption kinetics resulting from the surface chemical action of electrophilic gases at lower or room temperature. This work presents results of the feasibility study focused on improving hydriding kinetics and poisoning-tolerance, which are prerequisites properties that a material should possess to be a suitable catalyst precursor for Sabatier reaction, of the metal hydride (MH) materials. The studies in this work included: (i) element substitution and (ii) surface modification procedure. The substrate alloys investigated had the compositions LaNi4.8-xSnx and TiMn1.52, where x was 0.2. The activation performances of the materials were estimated by measurement of H2 absorption kinetics in the absence of vacuum heating, after long-term exposure to air. The presence of oxide layers on the alloy surface resulted in the deterioration of H sorption kinetics for the parent alloys. To overcome impurity effects, surface-modification technique through autocatalytic palladium deposition was employed. The activation performances and kinetics of the surface-modified were found to be superior to that of the unmodified AB2 and AB5 alloys. Based on this observation, it was seen that surface-modified MH materials based on the alloy substrate and Pd nanostructured coatings may be utilised as catalysts precursors for CO2 reduction into hydrocarbons.