(Invited) Contributions of Phase, Sulfur Vacancies, and Edges to the Hydrogen Evolution Reaction Catalytic Activity of Porous Molybdenum Disulfide Nanosheets

Abstract

Contributions of Phase, Sulfur Vacancies, and Edges to the Hydrogen Evolution Reaction Catalytic Activity of Porous Molybdenum Disulfide Nanosheets Ying Yin,1 Jiecai Han,1 and Bo Song2, * 1Centre for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080, China 2Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080, China Molybdenum disulfide (MoS2) is a promising non-precious catalyst for the hydrogen evolution reaction (HER) that has been extensively studied due to its excellent performance, but the lack of understanding on the factors that impact its catalytic activity hinders further design and enhancement of MoS2-based electrocatalysts. Here, by using novel porous MoS2 nanosheets synthesized through a liquid ammonia-assisted lithiation route, we systematically investigated the contributions of crystal structure (phase), edges, and sulfur vacancies (S-vacancies) to the catalytic activity towards HER from five representative MoS2 nanosheet samples, including 2H and 1T-phase, porous 2H and 1T-phase, and sulfur compensated porous 2H-phase. Superior HER catalytic activity was achieved in the porous 1T-phase MoS2 nanosheets that have even more edges and S-vacancies than conventional 1T-phase MoS2. A comparative study revealed that not only phase serves as the key role in determining the HER performance, as 1T-phase MoS2 always outperforms the corresponding 2H-phase MoS2 samples, but also both edges and S-vacancies also contribute significantly to the catalytic activity in porous MoS2 samples. Then, using combined defect characterization techniques of electron spin resonance (ESR) spectroscopy and positron annihilation lifetime spectroscopy (PALS) to quantify the S-vacancies, the contributions of each factor were individually elucidated. This study presents new insights and opens up new avenues for designing electrocatalysts based on MoS2 or other layered materials with enhanced HER performance. *Corresponding Author: songbo@hit.edu.cn