Analysis of hydrogen and deuterium absorption kinetics in Pd nanofilms

An electrochemical quartz crystal microbalance was used to study the kinetics of hydrogen or deuterium absorption in a Pd nanofilm. The Pd film in a thickness of 120 nm was deposited on a quartz crystal. Hydrogen was electrolytically charged into the film and monitored by the frequency shift from the microbalance. The kinetics curves of hydrogen or deuterium absorption in the nano-scaled Pd thin film were obtained at reduction potentials ranging from -1.2 to -1.5 V. Based on the Fickʹs law, the diffusion rates of hydrogen or deuterium in the film were slower than those in bulk Pd by several orders of magnitude. It is proposed that surface effect was the dominant factor for hydrogen/deuterium absorption in the nano-scaled Pd film. By modifying the Fickʹs law with a first order reaction equation, the kinetics could be interpreted by a surface-controlled process.