Nickel-Based Selenides with a Fractal Structure as an Excellent Bifunctional Electrocatalyst for Water Splitting

Nickel-based selenides are believed to be promising non-precious metal electrocatalysts, and have been widely used for both oxygen evolution reactions (OER) and hydrogen evolution reactions (HER). Here, we control the aging time to prepare Ni(x)Se(y) with different fractal structures as a bifunctional catalyst. An obtained sample with an aging time of 80 min shows outstanding electrocatalytic performance for hydrogen evolution reactions (HER) with an overpotential of 225 mV (η@10 mA/cm(2)) and for oxygen evolution reactions (OER) with an overpotential of 309 mV (η@50 mA/cm(2)). Moreover, to further improve catalytic activity, we doped Fe in Ni(x)Se(y) to obtain the ternary nickel-based selenide, Fe(0.2)Ni(0.8)Se (FNSs). The HER activity of FNS increased two-fold at 10 mA/cm(2), and the overpotential of OER decreased to 255 mV at 50 mA/cm(2). The synthetic strategy and research results of this work have a certain reference value for other low-cost and high-efficiency transition metal catalysts for electrocatalytic water splitting.