Highly active and stable layered ternary transition metal chalcogenide for hydrogen evolution reaction

Highlights: • Single layered ternary transition metal chalcogenides have been synthesized for highly active and stable electrocatalyst. • Se-doping plays an essential role to exfoliate Cu₂Mo(S_1-ySe_y)₄ for high electrochemical active surface. • Se-doping strategy can be implemented to exfoliate and enhance electrocatalytic activity of transition metals chalcogens. Layered ternary transition metal chalcogenides (TTMCs) material has great potentials that can overcome to the limitation of active sites which is challenging in binary transition metal chalcogenides (BTMC), such as MoS₂, towards electrochemical hydrogen production. Here, we demonstrate TTMC material which contains two transition metals Cu and Mo with chalcogen S. The TTMC, Cu₂MoS₄ has been successfully synthesized by a facile solution-processed method. Moreover, by anion doping such as Se in as the synthesized Cu₂MoS₄, it has been found that TTMC can be exfoliated into single layer nanosheets. Furthermore, by controlling the number of layers, single layers TTMC exhibit the highest electrocatalytic activity towards hydrogen evolution reaction (HER) because the single layers can provide more catalytic active sites than multilayers and bulk. The onset potential for hydrogen generation is −96 mV for single layer TTMC electrode material with corresponding Tafel slope 52 mV/decade. After 1000 cycles with continuous electrolysis in acid electrolyte for 15 h, the electrode material preserves its structure and robust catalytic activity perfectly. Our new TTMC materials show highly active electrocatalytic performance and high stability which overcome the intrinsic limitation of BTMC. As a result, our work can guide new strategy for the developments of real applications of TMCs in HER.