Improving hydrogen evolution activity of two-dimensional nanosheets MoNi 4 /MoO 2.5 -NF self-supporting electrocatalyst by electrochemical-cycling activation

Alloys, especially Mo–Ni alloys, are excellent HER electrocatalysts in alkaline solution. The HER activity of the Mo–Ni alloys can be improved by grafting H 2 O dissociation promoters (metal oxides or hydroxides) to promote the dissociation of H 2 O in alkaline solution. However, most of the reported Mo–Ni alloys grafting with H 2 O dissociation promoters only have simple one-dimensional (1D) structures, which cannot further improve the catalytic performance. Compared with 1D nanomaterials, two-dimensional (2D) nanomaterials have higher specific surface area, electrical conductivity, more exposed active sites and mass transfer channels. Herein, a novel 2D nanosheets self-supporting composite electrocatalyst MoNi 4 /MoO 2.5 -NF derived from the NiMoO 4 nanosheets was reported for the first time. Benefiting from the unique 2D nanosheets structure and the synergistic effect of each component, the catalyst shows high electrocatalytic HER activity in 1 M KOH solution. The MoNi 4 /MoO 2.5 -NF needs overpotential of 49 mV to reach 10 mA cm −2 . The HER activity of MoNi 4 /MoO 2.5 -NF can be further improved through electrochemical-cycling activation (CV) process. After 10 CV cycles, the overpotential to reach 10 mA cm −2 of the catalyst decreased from 49 to 27 mV and even exceeded 20% Pt/C (32 mV). The improvement of HER performance is attributed to the increase in the electrochemically active surface area, the reduced impedance and Tafel slope after CV process. Graphical abstract