Fig. 2: Synthetic approach of double-layer Pt NSs.

a Layered K_yPtO_x was synthesized by the solid-state-reaction of a mixture of K₂CO₃ and PtO₂. b The acid-treated form, layered H_yPtO_x, was prepared via the ion-exchange reaction. c PtO_x NS was obtained via exfoliation of layered H_yPtO_x. d Pt NS was synthesized via topotactic reduction of PtO_x NS.