Au/Pd core-shell nanoparticles (NPs) were employed to study electro-oxidation mechanism of formate-based solutions. A series of combined studies including Raman spectroscopy, electrochemical stripping analysis, and computational simulations were conducted to understand electro-oxidation of formate-based solutions on the Au/Pd NPs. Compared to the commercial Pd black, the Au/Pd NPs showed superior catalytic activities, especially when using concentrated formate solutions. CO stripping test in conjunction with in situ Raman studies showed a lower oxidation potential (0.6 V vs. Ag/AgCl) of CO on the Au/Pd NPs than the Pd black (>0.6 V). This indicated a strong electronic coupling between Au and Pd in the core-shell NPs which could enhance the oxidation of formate species. In addition, theoretical studies suggested lower formate and hydroxyl coverages at the same applied potential for the Au/Pd NPs than the Pd black in the formate-based solutions, shedding lights on their superior formate-oxidizing ability. Crown Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.