A multi-step induced strategy to fabricate core–shell Pt–Ni alloy as symmetric electrocatalysts for overall water splitting

Devising an electrocatalyst with brilliant efficiency and satisfactory durability for hydrogen production is of considerable demand, especially for large-scale application. Herein, we adopt a multi-step consequential induced strategy to construct a bifunctional electrocatalyst for the overall water splitting. Graphene oxide (GO) was used as a carbon matrix and in situ oxygen source, which was supported by the octahedral PtNi alloy to form the Pt_xNi_y–GO precursor. When calcinating in Ar atmosphere, the oxygen in GO induced the surface segregation of Ni from the PtNi octahedron to form a core–shell structure of Pt_x@Ni_y. Then, the surface- enriched Ni continuously induced the reformation of C in reduced graphene oxide (rGO) to enhance the degree of graphitization. This multi-step induction formed a nanocatalyst Pt_x@Ni_y–rGO which has very high catalytic efficiency and stability. By optimizing the feeding ratio of PtNi (Pt: Ni = 1:2), the electrolytic overall water splitting at 10 mA·cm⁻² can be driven by an electrolytic voltage of as low as 1.485 V, and hydrogen evolution reaction (HER) only needs an overpotential of 37 mV in 1.0 M KOH aqueous solution. Additionally, the catalyst exhibited consistent existence form in both HER and oxygen evolution reaction (OER), which was verified by switching the anode and cathode of the cell in the electrolysis of water. This work provides a new idea for the synthesis and evaluation of the bifunctional catalysts for water splitting.