Hydrogen generation due to water splitting on Si - terminated 4H-Sic(0001) surfaces

• Published in: Surface science 2018-02, Vol.668, p.68-72
• Main Authors: Li, Qingfang, Li, Qiqi, Yang, Cuihong, Rao, Weifeng
• Format: Article
• Language: English
• Subjects: Barriers; Chemical reactions; First principles; First-principles calculation; Hydrogen production; Hydrogenation; Reaction mechanisms; Semiconductors; SiC surface; Silicon carbide; Vacancies; Vacancy defects; Water; Water splitting
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2017.10.017

•The first H splitting from water on the 4H-SiC(0001) surface can occure with ground-state electronic structure.•The C and Si vacancies can form easier in SiC(0001) surface than in SiC bulk and nanoribbons.•The introduction of C/Si vacancies can enhance photocatalytic activities of SiC(0001) surface. [Display omitted] The chemical reactions of hydrogen gas generation via water splitting on Si-terminated 4H-SiC surfaces with or without C/Si vacancies were studied by using first-principles. We studied the reaction mechanisms of hydrogen generation on the 4H-SiC(0001) surface. Our calculations demonstrate that there are major rearrangements in surface when H2O approaches the SiC(0001) surface. The first H splitting from water can occur with ground-state electronic structures. The second H splitting involves an energy barrier of 0.65 eV. However, the energy barrier for two H atoms desorbing from the Si-face and forming H2 gas is 3.04 eV. In addition, it is found that C and Si vacancies can form easier in SiC(0001)surfaces than in SiC bulk and nanoribbons. The C/Si vacancies introduced can enhance photocatalytic activities. It is easier to split OH on SiC(0001) surface with vacancies compared to the case of clean SiC surface. H2 can form on the 4H-SiC(0001) surface with C and Si vacancies if the energy barriers of 1.02 and 2.28 eV are surmounted, respectively. Therefore, SiC(0001) surface with C vacancy has potential applications in photocatalytic water-splitting.