Three-dimensional porous Au nanocoral structure decorated with Pt submonolayer via galvanic displacement of copper adatoms for electrooxidation of formic acid

Three-dimensional (3D) porous Au nanocoral network (GNN) structure was fabricated on glassy carbon (GC) electrode by one-step, template-free electrodeposition and decorated with ultrathin Pt film by combining the underpotential deposition (UPD) of copper adatoms and the galvanic displacement (GD) between PtCl₆^2- and Cu. The thickness of Pt atomic layers can be controlled precisely by repeating the UPD–GD process. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) were employed to characterize the morphology of GNN and Pt_n/GNN (n, the cycles of repeating the UPD–GD process). Cyclic voltammometric and chronoamperometric tests indicate that all Pt_n/GNN samples effectively support the direct oxidation of formic acid and show higher electrocatalytic performance than the commercial Pt/C catalyst (Pt, 20 wt %, Johnson Matthey Co.), where Pt₁/GNN completely eliminates the indirect oxidation of formic acid, exhibiting the best electrocatalytic activity and stability among all Pt_n/GNN samples due to the optimal coverage and distribution of Pt atoms on GNN.