▎ 摘　　要

Great interests have been focused on high entropy alloys, a new class of single-phase solid solution materials, because of their unique physical and chemical properties. Herein, CoNiCuMgZn high entropy alloy (HEA) has been homogeneously embedded onto ultrathin two-dimensional (2D) holey graphene conducting substrates via a simple anchoring and alloying strategy. During the growth of the HEA, graphene oxide is employed as both direct template and reductant. By modulating the initial input amounts of metal sources, the particle sizes of HEA can be finely regulated from 40 to 200 nm. Benefiting from the synergistic effect between the excellent electronic conductivity of graphene and the abundant catalytic sites of HEA particles, the obtained material displays remarkable catalytic activity and stability for hydrogen evolution reaction compared to previous reported nonnoble-metal catalysts. The density functional theory calculation unveils that the unique embedded structure of HEA onto graphene benefits to the H* sorption and promotes the catalytic kinetics. This work is of great importance in the practical utilization of HEA and indeed give a brilliant perspective in fabricating HEA as efficient electrocatalysts for water splitting.