Abstract
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 NixSey 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/cm2) and for oxygen evolution reactions (OER) with an overpotential of 309 mV (η@50 mA/cm2). Moreover, to further improve catalytic activity, we doped Fe in NixSey to obtain the ternary nickel-based selenide, Fe0.2Ni0.8Se (FNSs). The HER activity of FNS increased two-fold at 10 mA/cm2, and the overpotential of OER decreased to 255 mV at 50 mA/cm2. 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.
Highlights
Hydrogen from water electrolysis has been sought after for industrial applications, because of its characteristics of a high energy density and zero emissions [1,2]
The X-ray diffraction (XRD) patterns are shown in Figure 1a, including those of prepared Nix Sey samples with different aging times
Through the X-ray photoelectron spectroscopy (XPS) results and electrochemical characterization of Nix Sey samples at different aging times, we found that this performance is the result of the comprehensive effects of many aspects, including the number of active sites in the electrochemical reaction, the valence of Ni, and the electrochemical impedance of the samples
Summary
Hydrogen from water electrolysis has been sought after for industrial applications, because of its characteristics of a high energy density and zero emissions [1,2]. By variating the aging time, the Nix Sey obtained at 80 min (168 ◦ C) showed the best catalytic activity, both for HER (225 mV at 10 mA/cm2 ) and OER (309 mV at 50 mA/cm2 ) Based on this method, we synthesized the ternary transition metal selenide, Mx Niy Sez (M = Fe, Mn and V), catalysts with different 3d electron numbers to achieve a local electron distribution [10,33,34,35,36]. We synthesized the ternary transition metal selenide, Mx Niy Sez (M = Fe, Mn and V), catalysts with different 3d electron numbers to achieve a local electron distribution [10,33,34,35,36] Among these samples, Fe0.2 Ni0.8 Se showed the best bifunctional electrochemical activities, and the overpotential of HER and OER were 124 mV (at 10 mA/cm2 ) and 255 mV (at 50 mA/cm2 ), respectively. These results may shed light on the mechanisms of designing high-performance 3d metal-based catalysts
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