Activating MoS basal planes for hydrogen evolution through direct CVD morphology control

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2019-12, Vol.7 (48), p.2763-27611
• Main Authors: Dong, Lianqing, Guo, Shaoqiang, Wang, Yuyan, Zhang, Qinghua, Gu, Lin, Pan, Caofeng, Zhang, Junying
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c9ta08738a

Monolayer MoS 2 has emerged as an active and non-precious electrocatalyst for electrochemical hydrogen production. The atomic thinness and ultrahigh surface-to-volume ratio of the chemical vapor deposition (CVD)-grown monolayers result in an ideal material to facilitate efficient electrochemical hydrogen evolution and explore the mechanism at the atomic level. However, the active sites of pristine monolayer MoS 2 are reported to locate at the edges, leaving the basal planes inert, which limits their hydrogen evolution reaction performance. Here, we synthesize monolayer MoS 2 hexagonal flakes with high surface coverage and abundant highly distributed S vacancies as active reaction sites directly by CVD. The catalytic performance of the hexagonal MoS 2 flakes presented here is superior to that of the existing as-grown MoS 2 , exhibiting a current density of 100 mA cm −2 at −353 mV versus the reversible hydrogen electrode (RHE) with an extraordinarily low onset potential of only 41 mV. And an outstanding exchange current density of 0.091 mA cm −2 stands as the highest ever reported for all kinds of non-precious-metal doped MoS 2 catalysts. It is proved by a variety of tests that abundant S vacancies are distributed in the highly crystalline basal plane of hexagonal MoS 2 , which leads to a remarkably improved catalytic efficiency compared with that of the triangular one. The monolayer MoS 2 is further evidenced to have excellent long-term stability and high durability, maintaining a stable performance for nine months in air and retaining the initial performance after 6000 cyclic voltammetry scans. On-site defect engineering of monolayer MoS 2 for excellent hydrogen evolution reaction (HER) performance enriches insights into the structure-performance relationship in 2D materials and provides new opportunities for the design of highly active catalysts. Monolayer hexagonal MoS 2 flakes with abundant sulphur vacancies directly grown by CVD have remarkably improved catalytic efficiency compared with the triangular ones, superior to existing MoS 2 grown by CVD for electrochemical hydrogen production.