Hydrogen production: a DFT study of the hydrogen/ iron-nickel cell interactions

S. SIMONETTI; I. SALAZAR-EHUAN; G. CANTO

Conferencia; 20th World Hydrogen Energy Conference 2014; 2014

The reaction between Fe90Ni10 and Fe95Ni5 alloys, and water has been investigated by Hirao et al. The hydride formed is smaller in the iron-nickel-water system than in the iron-water system, although the hydrogen content in iron-nickel hydride is not significantly different. The results indicate that the existence of nickel in iron tend to reduce the amount of hydrogen supplied. The effect on the hydrogen production depends upon the metal added. As general feature, during the acidogenesis phase, nickel reduces, while iron increases, the percentage of dihydrogen in the biogas. We have performed calculations using the SIESTA code to study the interactions of hydrogen in a Fe50Ni50 cell. H debilitates the original metal-metal bonds by forming strong H-metal interactions. The Fe-H interaction is stronger than the Ni-H interaction. The H-metal exchange contributes to this process. After H adsorption, the strength of the nearest Fe-Fe, Fe-Ni and Ni-Ni bonds decreases to about 89 %, 15% and 1%, respectively. Then, the Fe-Fe bond is the most affected. The adsorption of additional H atoms modified the metal-metal strength in a lesser percent but more metallic bonds are affected. The H-H interaction is small; then, an H2 molecule is not formed.