Noble-Metal-Free MoS₂ Platelets with Promising Catalytic Performance in Hydrogen Evolution Reaction for the Post-Lithium-Ion Battery

In search of a practical alternative catalyst to costly and rare noble metals for hydrogen evolution reaction (HER), here we propose a lamellar electrode architecture out of engineered 2D MoS2 platelets that are stable in harsh electrochemical conditions, densified in the catalytically active sites, and enhanced in the interlamellar charge transfer. Energetic ion bombardment such as Ar ion beam milling (IBM) as a large-scale surface engineering technique can successfully create numerous edge states onto the MoS2 lamella with an observable penetration depth of ∼10 nm for the first time, leading to an excellent onset overpotential of 33.3 mV at 0.1 mA/cm2. Interlamellar charge transfer enhancement by raising the metallic portion of 1T-phase MoS2 and also by inserting conductive rGO platelets in the lamella turns out to improve the HER catalytic activity remarkably. The promising results obtained in an aqueous electrolyte with rarely reported 1 M LiOH imply a potential use in seawater splitting toward energy carrier storage. Equipped in a Li–water battery cell, our engineered MoS2 lamella electrode reveals, for the first time, a remarkable discharge performance supplying >2.2 V stably for more than 2.5 days, lending it potential adaptability to energy storage systems such as battery and fuel cells.