In situ visualization of ultrafast electrocatalyst on MoS2 during hydrogen evolution reaction

C-W Luo
National Yang Ming Chiao Tung University,

Keywords: hydrogen evolution reaction, HER, ultrafast carrier dynamics, transient transmittance changes, catalyst


Because of the ultrathin nature of two-dimensional (2D) transition metal dichalcogenides (TMDs) catalysts, the buildup of electrolyte ions across the nanometer-scale electrochemical double layer (ECDL) may cause the formation of excitons and trions in monolayer (ML)-MoS2 during hydrogen evolution reaction (HER), similar to those observed in gate-controlled FET devices. Using the distinct carrier relaxation dynamics of excitons and trions as sensitive descriptors, an in-situ micro-cell-based ultrafast time-resolved liquid cell microscopy (TR-LCM) is setup to simultaneously probe the ultrafast carrier dynamics and electrochemical reactions at ML-MoS2 catalyst during HER process. It is found that the whole surface of MoS2 becomes “trion-dominant” as the potential is at HER-on state while it becomes “exciton-dominant” as the potential is at HER-off state. Through 2D mapping image on the evolution of the individual constituents of excitons and trions on ML MoS2 surface during HER, the interplay between exciton/trion dynamics and electrocatalytic activity of ML MoS2 affected by electrolyte gating during HER process can be unequivocally revealed. This in-situ probing technique provides an excellent platform to explore carrier behaviors at the atomic layer/liquid electrolyte interfaces during electrocatalytic reaction of 2D TMDs.