Experimental and theoretical investigation of the cycle durability against CO and degradation mechanism of the LaNi5 hydrogen storage alloy

First-principles investigation of LaMg2Ni and its hydrides

“…This suggests Ni atom is an active site on La-Mg-Ni alloy surface for H adsorption. Similar result is found on La-Ni systems 25,26 . It is worth noting that a H-adsorbed LaMg 2 Ni (100) system with relatively lower hydrogen absorption energy exhibits rather weaker Ni-H interactions, as noted E ads = − 0.565 eV and BO s…”

“…The exchange-correlation function was treated by the generalized gradient approximation of Perdew-Wang 91 (GGA-PW91) 22 . The ultrasoft pseudopotentials with valence states 5s 2 5p 6 5d 1 6s 2 for La, 2p 6 3s 2 for Mg, 3d 8 4s 2 for Ni and 1s 1 8,[11][12][13] , and Ni atom on La-Ni alloy surface has good catalysis on the surface activity and the initial steps of hydrogen storage (hydrogen adsorption and dissociation) [24][25][26] . For these facts, here, the initial positions of H on LaMg 2 Ni (100) surface is on the bridge site of La-Ni atoms, the top site of La atom and the top site of Ni atom, as shown in Fig.…”

High temperature hydrogenation of Ti–V alloys: The effect of cycling and carbon monoxide on the bulk and surface properties

“…7). A similar recovery of the hydrogenation behavior has also been observed to occur during low temperature cycling of LaNi 5 [30] and TieMn alloys [9] in hydrogen gas containing, respectively, 0.1 and 0.5% CO. The reason for this recoverability is probably associated with removal of carbon/carbon monoxide from the alloy surface and thus reactivation of the active sites for hydrogen adsorption.…”

“…This agrees well with the results of an investigation on LaNi 5 [10], showing that, at high interaction temperatures above 300 C, CO decomposes at the metal surface, leading to deposition of carbon and formation of methane and a surface oxide. Even at low interaction temperatures, CO has been shown to dissociate on a LaNi 5 surface, but at those conditions the reaction products were methane and H 2 O [30]. The effect of carbon contamination appears to be related to the gas composition and temperature, and it has been shown in previous works that gas mixtures containing carbon monoxide reduce the number of active surface sites for metalehydrogen interaction [23,24,31].…”

CO Adsorption on a LaNi5 Hydrogen Storage Alloy Surface: A Theoretical Investigation

“…[5,6] Extensive experimental work has been done on their structures and properties, and theoretical calculations based on DFT have made important contributions to the understanding of their structures and stabilities. [7][8][9] For practical applications, hydrogen storage alloys must resist deterioration due to unavoidable impurities, such as carbon monoxide, present in hydrogen produced by steam reforming. [10] Work on the hydrogen absorbing-desorbing cycle durability by using H 2 with 300 ppm O 2 , H 2 O or CO has revealed that the presence of CO has the severest effect on hydrogen storage ability.…”