Self-Assembled Coral-like Hierarchical Architecture Constructed by NiSe₂ Nanocrystals with Comparable...

For the first time, self-assembled coral-like hierarchical architecture constructed by NiSe₂ nanocrystals has been synthesized via a facile one-pot DMF-solvothermal method. Compared with hydrothermally synthesized NiSe₂ (H-NiSe₂), the DMF-solvothermally synthesized nanocrystalline NiSe₂ (DNC-NiSe₂) 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/cm² 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 NiSe₂-based catalysts, and even lower than that of precious platinum (Pt) catalyst (30.8 mV dec^-1). The superior HER performance of DNC-NiSe₂ 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 NiSe₂ nanocrystals. The DNC-NiSe₂ is promising to be a viable alternative to precious metal catalysts for hydrogen evolution.