Perpendicularly anchored ReSe2 nanoflakes on reduced graphene oxide support for highly efficient hydrogen evolution reactions.

• Few-layered ReSe 2 nanoflakes are vertically arranged on rGO. • Mechanism of vertical growth of ReSe 2 on rGO is clarified by DFT calculation. • Plentiful exposed edges/corners on ReSe 2 facilitate the generation of active sites for electrocatalysis. • Improved electrical conductivity and electrochemical stability of ReSe 2 are realized after hybrid with rGO. • Prominent HER performance is measured with a low overpotential and small Tafel slope. Hydrogen evolution reaction (HER) by water splitting has made a significant contribution to producing large amounts of hydrogen gas as the next generation fuel. Development of highly efficient, economically viable, and electrochemically stable HER electrocatalysts has accordingly become a prerequisite for practical implementation of large scale water electrolysis. Mono/few-layered transition metal dichalcogenide (TMD) based HER-electrocatalysts have recently garnered great interest due to their diverse tunable electrochemical properties. However, they still face intrinsic limitations such as self-aggregation, rare active sites, high electrical resistance, and long-term electrochemical instability. To tackle these challenges, we designed and synthesized a novel electrocatalyst comprising active site-rich rhenium diselenide (ReSe 2) nanoflakes perpendicularly anchored on a reduced graphene oxide (rGO) nanosheet support via a facile one-step hydrothermal synthesis. The rGO support provides a growing platform for few-layered ReSe 2 nanoflakes while facilitating plentiful exposure of edge/corner sites of ReSe 2 , highly desirable for maximizing the catalytic activity of ReSe 2 @rGO. The synthesized ReSe 2 @rGO exhibits a low overpotential of 145.3 mV at a current density of 10 mA·cm−2 with a Tafel slope of 40.7 mV·dec−1 for the HER process due to the synergistic combination of high surface density of unsaturated coordination sites, remarkably accelerated electron transfer, and enhanced electrochemical stability. This outcome suggests using structurally regulated hybridization of TMDs and graphene as a platform toolkit for developing high performance HER catalysts. [ABSTRACT FROM AUTHOR]