Two-dimensional (2D) transition metal dichalcogenides (TMDs) have been made in improving the NRR for the significant effort in catalytic activity due to its unique crystal structures, electronic properties, and promising nonprecious catalysts. However, many studies have provided solutions to activate the inert basal plane with low improvement. With highly asymmetric configuration, Janus monolayer with intrinsic strain and electric field can enable a way to tune the activity in TMDs-based catalysts. Although the first successful experimental synthesis of Janus structure (MoSSe) has gained significant interest and become a fast-growing TMDs-based material, the structure remains limited in the low dimensional and hard to expose the edges site to enhance the catalytic activity. Besides the common benefits of 2D TMDs, such as high surface area, short carrier migration distance, and tunable electronic structure. In this regard, the inherent structural asymmetry of Janus WSSe nanowalls as a new means to enhance the NRR activity was investigated. Janus TMDs nanowalls as the catalyst by taking advantage of its introduction of in-gap states with a shift in the Fermi level in nitrogen adsorbed system because of Janus asymmetry from the origin of stimulating NRR activity. Raman spectra showthe related main modes for WSSe Janus structure as shown in Fig. 1a, for which peaks at 271 and 333 nm can be found, respectively. The linear sweep voltammetric (LSV) curves of the catalysts as shown in Fig. 1b confirm the onset potential of the NRR, which increases with the different materials. Janus WSSe Janus nanowalls exhibit outstanding NRR performance over its parent materials (WS₂ and WSe₂). The results should propose a new path to design high performance and a novel structure for Janus TMD-based catalysts.

Fig1. (a) Evolution of Raman spectra in the WSSe nanowalls as a function of chemical composition (b) LSV curves for WS₂, WSe₂, WS_2-XSe_2-2X alloy, and WSSe Janus nanowalls