Substantial efforts have been devot

Substantial efforts have been devoted for developing clean energy and replacing fossil fuels to achieve sustainable improvement and environmental conservation of human society. Electro-chemical hydrogen evolution reaction (HER) has recently attracted attention as a promising clean and renewable energy technology [1–5]. Noble metal Pt is currently the state-of-the-art catalyst for electrocatalytic HER. Unfortunately, the wide-range usage of Pt is limited by its scarcity and high cost. Therefore, earth-abundant and efficient electrocatalysts must be urgently developed.Transition metal dichalcogenides (TMDCs), such as MoS2, CoS2,and NiS2, have been widely studied in various areas due to their unique mechanical and electronic properties which render their numerous potential applications in catalysis, lithiumbatteries, and hydrogen storage. Among TMDCs, MoS2 is a layered compound with atoms within the layer covalently bonded with layers coupled through weak Van de Waals interactions. This material shows great potential as an electrocatalyst for HER because of its abundant exposed edge sites and electron transfer-favoring layered structure. Unfortunately, MoS2 only performs efficiently as a catalyst in a strongly acidic solution. Its activity in neutral and alkaline solutions is relatively poor due to its unstable properties at high pH, thus limiting its application in water splitting systems. Therefore, cost-effective HER catalysts that are efficient over a wide pH range must be developed.