Self-Assembled Coral-like Hierarchical Architecture Constructed by NiSe2 Nanocrystals with Comparable Hydrogen-Evolution Performance of Precious Platinum Catalyst

For the first time, self-assembled coral-like hierarchical architecture constructed by NiSe 2 nanocrystals has been synthesized via a facile one-pot DMF-solvothermal method. Compared with hydrothermally synthesized NiSe 2 (H-NiSe 2 ), the DMF-solvothermally synthesized nanocrystalline NiSe 2 (DNC-NiSe 2 ) exhibits superior performance of hydrogen evolution reaction (HER): it has a very low onset overpotential of ∼136 mV (vs RHE), a very high cathode current density of 40 mA/cm 2 at ∼200 mV (vs RHE), and an excellent long-term stability; most importantly, it delivers an ultrasmall Tafel slope of 29.4 mV dec –1, which is the lowest ever reported for NiSe 2 -based catalysts, and even lower than that of precious platinum (Pt) catalyst (30.8 mV dec –1 ). The superior HER performance of DNC-NiSe 2 is attributed to the unique self-assembled coral-like network, which is a benefit to form abundant active sites and facilitates the charge transportation due to the inherent high conductivity of NiSe 2 nanocrystals. The DNC-NiSe 2 is promising to be a viable alternative to precious metal catalysts for hydrogen evolution.