Synthesis of Janus MoSSe on Ti-Au and its application for One-Step lithography fabrication of electrochemical micro-reactors

• Preparation of Janus MoSSe on Ti-Au substrates at room-temperature. • Different electronic conditions for MoS 2 lead to different reaction results. • Development of a method for rapid preparation of electrochemical devices. The prevalent method for synthesizing Janus transition metal dichalcogenides (Janus TMD) generally involves replacing the top layer chalcogen atoms in a monolayer TMD precursor with a different chalcogen atoms. Numerous studies have investigated various techniques for Janus TMD synthesis, but there is a notable gap in literature regarding their formation on conductive substrates. Our research bridges this gap by demonstrating the successful fabrication of Janus MoSSe on Ti-Au substrates using a room-temperature plasma-assisted substitution (RT-PAS) method. In contrast to the conditions of converting MoS 2 to Janus MoSSe on sapphire and SiO 2 /Si substrates, the conversion process on Ti-Au substrates requires significantly higher hydrogen plasma energy or longer irradiation time. The discrepancies in the interaction between MoS 2 and hydrogen plasma across diverse substrates were elucidated by using Raman spectroscopy, the first-principles calculations and X-ray photoelectron spectroscopy analysis. Subsequently, we employed a one-step lithography process to construct electrochemical micro-reactors on the Ti-Au substrates, and it is revealed that Janus MoSSe outperforms pristine MoS 2 in hydrogen evolution reaction (HER) performance. This study sheds light on the intricate interactions between TMD materials and plasma within varied electronic environment, and paves a way for the rapid fabrication of devices tailored for microelectrochemical measurements of low-dimensional materials.