New Efficient Electrocatalyst for the Hydrogen Evolution Reaction: Erecting a V₂Se₉@Poly(3,4-ethylenedioxythiophene) Nanosheet Array with a Specific Active Facet Exposed

To obtain catalysts with remarkable activity for the hydrogen evolution reaction (HER), rational design and synthesis of catalysts with rich active sites are very urgent. Herein, we reported, for the first time, V 2 Se 9 nanosheet arrays exposed with the highly active (100) facet as a new efficient catalyst for HER. The highly active but thermodynamically instable (100) facet was converted from V 2 O 5 based on a low crystal-mismatch strategy. Furthermore, conductive poly(3,4-ethylenedioxythiophene) (PEDOT) acting as a co-catalyst further contributed to the redistribution of charge and reduction of hydrogen adsorption energy. Due to the strong synergistic effect between V 2 Se 9 and PEDOT, the resulting material, noted as V 2 Se 9 @PEDOT NSs/NF, exhibited excellent electrocatalytic performance among selenide catalysts, for example, a small overpotential of 72 mV at 10 mA cm –2, a low Tafel slope of 36.5 mV dec –1, and remarkable durability. Simultaneously, density functional theory (DFT) computations proved that the adsorption free energy of H* (Δ G H* ) for V 2 Se 9 @PEDOT NSs/NF (0.09 eV) is comparable to that of Pt (around 0.09 eV).