AB-INITIO STUDY OF HYDRAZINE DECOMPOSITION ON THE SURFACE OF CATALAYST M-NI(111) (M = PT, PD, RH, IR)

• Main Author: Irwansyah
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/75445
• Institution: Institut Teknologi Bandung

Hydrogen production plays a crucial role as a future energy source. Fuel cells are devices that utilize electrochemical reactions involving oxygen (O2) and hydrogen (H2) to generate electricity. One of the candidate sources of H2 used in fuel cells is hydrazine (N2H4), which contains 12.5% H2 content. H2 is produced through the decomposition of N2H4 on the catalyst surface via adsorption, reaction, and desorption stages. The use of catalysts in the N2H4 decomposition process is crucial in determining the stability of N2H4 adsorption and bond cleavage, either through N-H or N-N bond cleavage routes. Bimetallic catalysts based on nickel (Ni) with pure metal impurities have been indicated to produce H2 with high selectivity. Modeling and computational-based research can be employed to explore the mechanisms behind this high selectivity. Understanding these mechanisms can be utilized to design even better catalysts. Ab-initio methods based on Density Functional Theory (DFT) are employed to study the adsorption and bond cleavage reactions of N-N and N-H on various surfaces of M-Ni(111) catalysts (M = Pt, Pd, Ir, and Rh) and various possible sites. N2H4 can be adsorbed in three conformations: anti, gauche, and cis. The adsorption strength trend of N2H4 is found to follow the sequence Ir-Ni(111) > Rh-Ni(111) > Pt-Ni(111) > Pd-Ni(111), and the cis conformation is identified as the most stable conformation for all surfaces except for Ir-Ni(111). The calculation results reveal strong adsorption on Ir-Ni(111), which influences the preference of the structure towards the anti conformation. Thermodynamically, for all surfaces investigated in this study, N-N bond cleavage is found to be more favorable than N-H bond cleavage. However, the bond cleavage energy on Ir-Ni(111) indicates that N-H bond cleavage is the most exothermic compared to N-H bond cleavage on other surfaces. This indicates a tendency towards the selectivity of H2 production through N-N bond cleavage. Furthermore, variations in bond cleavage energies with respect to the position of N2H4 on various sites are also observed.