The green transition requires new strategies to develop active and stable nanomaterials for energy conversion. We describe the preparation of Pd-Au bimetallic nanocatalysts using a surfactant-free electrodeposition method in a deep eutectic solvent (DES) and test their electrocatalytic performance for the formic acid oxidation reaction (FAOR). We use choline chloride plus urea DES to tune the composition of Pd and Au in the bimetallic nanostructures, as well as their morphology and active surface area. We measure the increase in the electrochemically active surface area (ECSA) of the prepared Pd-Au bimetallic surfaces by Cu underpotential deposition (UPD). Our results indicate a surface area increase of 5 to 12-fold compared to Pd and PdAu extended polycrystalline electrodes. We observe that the higher activity of Pd-Au nanostructures is principally due to its increased active area. Our results also reveal that Pd-Au nanostructures with ca. 50% of Pd and Au display the best activity and stability in relation to the Pd mass loading proving the synergy between Pd and Au in the bimetallic catalyst. We highlight that an in-depth analysis of the ECSA, as well as surface and electronic structure effects in bimetallic nanostructures, are crucial aspects for the rationalization of their catalytic properties.
Complementary CVs, CAs of Pd-Au electrodeposition in DES from 0.025 M PdCl2: 0.075 M AuCl3 + DES, 0.05 M PdCl2: 0.05 M AuCl3 + DES and 0.075 M PdCl2: 0.025 M AuCl3 + DES are explained. Additional FE-SEM and EDS analysis of single Au and Pd and, Pd-Au bimetallic samples from 1Pd:3Au, 1Pd:1Au and 3Pd:1Au are included. The Cu UPD of a single Pd deposit and the polycrystalline Pd and Au with the PdAu alloy are also represented. The calculated charges from the CO stripping of the samples are summarized. The FAOR of the main samples and the stability test from the main three deposits (Pd, 3Pd:Au and, Pd:Au) versus the geometric area of the electrodes are shown for a better understanding.