Controlling the Reactivity and Interactions between Hydrogen and Palladium Nanoparticles via Management of the Particle Diameter

Tailoring the interactions between hydrogen and palladium is crucial for numerous industrial and research applications. The fine control of Pd nanoparticles (NPs) diameter is promising to address this problem when other means, i. e. temperature, pressure, or cell voltage, are set by the ongoing process. We investigate the electrochemical behaviour of Pd NPs in the presence of hydrogen over a large range of particle diameters, between 3.8–21.5 nm. The study is carried out in both a three-electrode setup and a proton pump. A linear relationship between the H/Pd ratios and the NPs diameter is evidenced. The increase in particle size is accompanied by an extension of the loading duration to reach a stable hydride. Beyond H absorption, the HER and HOR kinetics are examined as a function of the particle diameter. The smaller the particle the higher the catalytic activity, with exchange currents ranging between approx. 1.7–9.8 mA mg_Pd⁻¹.