Palladium nanoparticles (Pd NPs) were synthesised by the reduction-by-solvent method using polyvinylpirrolidone (PVP) as capping agent. The non-static interaction between PVP and the metallic surface may change the properties of the NPs due to the different possible interactions, either through the O or N atoms of the PVP. In order to analyse these effects and their repercussion in their catalytic performance, Pd NPs with various PVP/Pd molar ratios (1, 10 and 20) were prepared, deposited on silica and tested in the formic acid decomposition reaction. The catalytic tests were conducted using catalysts prepared by loading NPs with three different time lapses between their purification and their deposition on the silica support (1 day, 1 month, and 6 months). CO adsorption, FTIR spectroscopy, XPS and TEM characterisation were used to determine the accessibility of the Pd NPs surface sites, electronic state of Pd and the average NPs size, respectively. The H 2 production from the formic acid decomposition reaction has a strong dependence with the Pd surface features, which in turn are related to the NPs aging time due to the progressive removal of the PVP.