Se-Rich MoSe₂ Nanosheets and Their Superior Electrocatalytic Performance for Hydrogen Evolution Reaction

Ik Seon Kwon 권익선 (제1저자, 박사과정), In Hye Kwak, Tekalign Terfa Debela, Hafiz Ghulam Abbas, Yun Chang Park, Jae-pyoung Ahn, Jeunghee Park (박정희 교수님),*  and Hong Seok Kang*

ACS Nano 2020, 14, 6295-6304 (Impact factor: 14.588)

Abstract : Two-dimensional MoSe2 has emerged as a promising electrocatalyst for the hydrogen evolution reaction (HER), although its catalytic activity needs to be further improved. Herein, we report Serich MoSe2 nanosheets synthesized using a hydrothermal reaction, displaying much enhanced HER performance at the Se/Mo ratio of 2.3. The transition from the 2H to the 1T′ phase occurred as Se/Mo exceeded 2. Structural analysis revealed the presence of Se adatoms as well as the formation of Se−Se bonding. Based on first-principles calculations, we propose two equally stable Se-rich structures. In the first one, excess Se atoms bridge two MoSe2 layers via the interlayer Se−Se bonds. In the second one, the Se atoms substitute for the Mo atoms, and extra Se atoms are added closest to the Mo-substituted Se. Calculation of Gibbs free energy along the reaction path indicates that the Se adatoms of the second model are the most active sites for HER.