Annotation for the dissertation Pyrite type transition metal dichalcogenides for oxygen evolution Author's name: M.Sc. Yunpeng Zuo Supervisor's name: Ing. Kment Štěpán, Ph.D. Annotation Electrocatalytic water splitting is a green pathway to produce hydrogen in large quantities, which involves two half-reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). OER is the kinetic bottleneck of water splitting, which requires a high standard overpotential with the four-electron-proton-coupled processes, thus it is particularly important to develop OER catalysts. Pyrite-type transition metal dichalcogenides (MX2, where M = Fe, Co, Ni et al., and X = S or Se) have been promising electrocatalytic materials for the OER, but the catalysts still require further improvement due to the easy oxidization of surface atoms and the intrinsically low activity. Ongoing research found that multimetallic compounds generally have better water splitting activity than single metal compounds. Furthermore, boron-doping can effectively optimize the adsorption energy of OER intermediates. We focused on designing and synthesizing functionalized catalysts for the electrocatalytic water-splitting reaction. A range of pyrite-type transition metal dichalcogenides (MX2, where M = Fe, Co, Ni et al., and X = S or Se), especially boron-doped polymetallic sulfides and selenides were developed. Specially, we synthesized the FeCoNiBS in situ coated by amorphous FeCoNiBx and fabricated heteroepitaxial pyrite Ni-selenide through dual-cation substitution and boron doping as the efficient and durable heterogeneous catalysts for OER. The spherical aberration-corrected transmission electron microscopy clearly shows that the obtained sulfides exhibit different phases with an approximately 2 nm amorphous layer on the external surface. This hybrid catalyst exhibits superior OER activity with an attractive overpotential of 419.4 mV vs. RHE at 100 mA cm-2 in 1 M KOH solution and excellent stability over 10 h. The fabricated Ni-pyrite selenides showed a special crystallineamorphous structure. After dual-cation substitution and boron doping, the overpotential improved from 543 mV to 279.8 mV at 10 mA cm2 with Tafel slope from 161 to 59.5 mV dec1. In conclusion, our studies focused on building efficient pyrite-type transition metal dichalcogenides for OER. The cations and boron doping can modulate the intrinsic electronic structure of pyrite-type sulfide/selenide for highly active OER performance. The discoveries underscore the importance of modulating OER property by using multiple elements, which provides an advantageous method for engineering the electrical structure of pyrite-type sulfide/selenide for superior OER catalysis, as well as general guidance on the minimization of activity loss with valence engineering. Original publications: Yunpeng Zuo,et al. Valence engineering via dual-cation and boron doping in pyrite selenide for highly efficient oxygen evolution. ACS Nano, 2019, Volume 13, Issue 10, Pages 11469-11476.(IF: 15.88) Yunpeng Zuo,et al. Spatially confined formation of single atoms in highly porous carbon nitride nanoreactors. ACS Nano, 2021, Volume 15, Issue 4, Pages 7790-7798. (IF: 15.88) Yunpeng Zuo, et al. Self-reconstruction mediates isolated Pt-tailored nanoframes for highly efficient catalysis. J. Mater. Chem. A, 2021, Volume 9, Pages 22501-22508. (IF: 12.732)Annotation for the dissertation Pyrite type transition metal dichalcogenides for oxygen evolution Author's name: M.Sc. Yunpeng Zuo Supervisor's name: Ing. Kment Štěpán, Ph.D. Annotation Electrocatalytic water splitting is a green pathway to produce hydrogen in large quantities, which involves two half-reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). OER is the kinetic bottleneck of water splitting, which requires a high standard overpotential with the four-electron-proton-coupled processes, thus it is particularly important to develop OER catalysts. Pyrite-type transition metal dichalcogenides (MX2, where M = Fe, Co, Ni et al., and X = S or Se) have been promising electrocatalytic materials for the OER, but the catalysts still require further improvement due to the easy oxidization of surface atoms and the intrinsically low activity. Ongoing research found that multimetallic compounds generally have better water splitting activity than single metal compounds. Furthermore, boron-doping can effectively optimize the adsorption energy of OER intermediates. We focused on designing and synthesizing functionalized catalysts for the electrocatalytic water-splitting reaction. A range of pyrite-type transition metal dichalcogenides (MX2, where M = Fe, Co, Ni et al., and X = S or Se), especially boron-doped polymetallic sulfides and selenides were developed. Specially, we synthesized the FeCoNiBS in situ coated by amorphous FeCoNiBx and fabricated heteroepitaxial pyrite Ni-selenide through dual-cation substitution and boron doping as the efficient and durable heterogeneous catalysts for OER. The spherical aberration-corrected transmission electron microscopy clearly shows that the obtained sulfides exhibit different phases with an approximately 2 nm amorphous layer on the external surface. This hybrid catalyst exhibits superior OER activity with an attractive overpotential of 419.4 mV vs. RHE at 100 mA cm-2 in 1 M KOH solution and excellent stability over 10 h. The fabricated Ni-pyrite selenides showed a special crystallineamorphous structure. After dual-cation substitution and boron doping, the overpotential improved from 543 mV to 279.8 mV at 10 mA cm2 with Tafel slope from 161 to 59.5 mV dec1. In conclusion, our studies focused on building efficient pyrite-type transition metal dichalcogenides for OER. The cations and boron doping can modulate the intrinsic electronic structure of pyrite-type sulfide/selenide for highly active OER performance. The discoveries underscore the importance of modulating OER property by using multiple elements, which provides an advantageous method for engineering the electrical structure of pyrite-type sulfide/selenide for superior OER catalysis, as well as general guidance on the minimization of activity loss with valence engineering. Original publications: Yunpeng Zuo,et al. Valence engineering via dual-cation and boron doping in pyrite selenide for highly efficient oxygen evolution. ACS Nano, 2019, Volume 13, Issue 10, Pages 11469-11476.(IF: 15.88) Yunpeng Zuo,et al. Spatially confined formation of single atoms in highly porous carbon nitride nanoreactors. ACS Nano, 2021, Volume 15, Issue 4, Pages 7790-7798. (IF: 15.88) Yunpeng Zuo, et al. Self-reconstruction mediates isolated Pt-tailored nanoframes for highly efficient catalysis. J. Mater. Chem. A, 2021, Volume 9, Pages 22501-22508. (IF: 12.732)