He-Yun Du, Yi-Fan Huang, Deniz Wong, Mao-Feng Tseng, Yi-Hsin Lee, Chen-Hao Wang, Cheng-Lan Lin, Germar Hoffmann, Kuei-Hsien Chen & Li-Chyong Chen 

Nature Communications, 12, Article number: 1321 (2021)

https://www.nature.com/articles/s41467-021-21660-z

Abstract

Layered MoS₂ is considered as one of the most promising two-dimensional photocatalytic materials for hydrogen evolution and water splitting; however, the electronic structure at the MoS₂-liquid interface is so far insufficiently resolved. Measuring and understanding the band offset at the surfaces of MoS₂ are crucial for understanding catalytic reactions and to achieve further improvements in performance. Herein, the heterogeneous charge transfer behavior of MoS₂ flakes of various layer numbers and sizes is addressed with high spatial resolution in organic solutions using the ferrocene/ferrocenium (Fc/Fc⁺) redox pair as a probe in near-field scanning electrochemical microscopy, i.e. in close nm probe-sample proximity. Redox mapping reveals an area and layer dependent reactivity for MoS₂ with a detailed insight into the local processes as band offset and confinement of the faradaic current obtained. In combination with additional characterization methods, we deduce a band alignment occurring at the liquid-solid interface.