Adsorption or deoxidation of H2 interacted with Fe3O4 surface under different H coverage: A DFT study

• Published in: Applied surface science Vol. 502; p. 144097
• Main Authors: Meng, Yu, Liu, Xiao-Yan, Bai, Miao-Miao, Chen, Juan, Ma, Ya-Jun, Wen, Xiao-Dong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2020
• Subjects: Density functional theory; Deoxidation; Fe3O4; H2 adsorption; Phase diagrams; Fe3O4; Density functional theory; H2 adsorption; Deoxidation; Phase diagrams
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2019.144097

[Display omitted] •For Fe3O4 surfaces, the surface O site is the most favorable adsorption site for H and the dissociated H2 is adsorbed on the adjacent surface O atoms to form surface OH.•Dissociation of H2 on Fe3O4 two surfaces are easy, and H easily migrates between O sites and from O to Fe sites.•The degree of reduction difficulty of surface O can be regulated by controlling the coverage of H by adjusting the reaction conditions. The adsorption and dissociation of H2, the migration ability of H atom, as well as the competition relationship between adsorption or deoxidation of H2 with increasing of H adsorption coverage on the Fe3O4 (1 1 1)-Fetet1 and (0 0 1)-B surfaces were systematically studied by DFT + U method. The adsorption energy and the optimal dissociation barrier of H2 on two Fe3O4 surface is about 0.04 eV and 1.0 eV, respectively. The surface O site is the most favorable adsorption site for H and the dissociated H2 is adsorbed on the adjacent surface O atoms. When H coverage is low, H preferentially adsorbs to the most stable O sites with the maximum adsorption heat. With the increasing of H coverage, the adsorption heat gradually decreases. When H coverage approaches saturated coverage, H2 reacted with surface O to form H2O become more favorable than direct adsorption. The phase diagrams of H adsorption/deoxidation at different temperature and pressure ranges were calculated. It can be found that the reduction of surface O become more favorable with the increasing of H coverage. The results indicate that the degree of reduction difficulty of surface O can be controlled by changing the coverage of H by adjusting the reaction condition.