Bimetallic modification of carbon electrodes through spontaneous deposition of Ag and Pd on cathodically pretreated substrates

In the present study, a new approach is proposed for the electrochemical synthesis of bimetallic heterostructures consisting of Pd and Ag. It is based on the possibility of spontaneous deposition of metals on different types of carbon electrodes (mesoporous carbon, MC, carbon nanofibers, CNF, and single-walled carbon nanotubes, SWCNT), cathodically pretreated in a supporting electrolyte, in the absence of deposited metal ions. The formation of the bimetallic nanoparticles (NPs) is achieved by subsequent deposition of metals in aqueous solutions of the respective metal salts without the addition of stabilizing species. The process is monitored by measuring open circuit potential (OCP) transients in the metal coating solutions. The metal NPs were characterized by SEM, EDX analysis and GDEOS. Examination of the two deposition sequences, Pd-Ag and Ag-Pd, shows that in both cases the surface density of the deposited NPs is on the order of 10 10 cm −2 . The average NP sizes depend on the type of carbon substrate and the deposition sequence, with the smallest NPs (13 nm) found for Pd-Ag in the case of MC and the largest NPs (33 nm) for Ag-Pd in the case of SWCNT. For all Ag-Pd/carbon samples, the NPs were found to be bimetallic, whereas in the case of Pd-Ag, in addition to the predominant number of bimetallic NPs, individual NPs consisting of only one of the two metals were also observed. The study opens a new perspective for the preparation of bimetallic NP electrocatalysts deposited directly on carbon substrates.