Quasitemplate synthesis of nanostructured palladium electroplates

By means of quasitemplate electrodeposition of palladium from palladium chloride solutions with additions of polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP), palladium deposits with high specific surface areas (up to 50 m(2) g(-1)) are synthesized. The specific surface areas of the deposits tend to increase with an increase in the chain length of a polymeric additive. Some of the deposits synthesized exhibit a high hydrogen sorption capacity and in this respect resemble the highly defective palladium deposits formed at hydride formation potentials in the absence of polymer additives. According to SEM and STM data, the details of globular micrometer-scale structure of the deposits depend on the polymer nature. PEG addition results in the oriented growth of the rows of nanoparticles, whereas PVP does not affect the mutual orientation of the latter. The minimal diameter of the imaged separated particles in the globulas equals 5 nm for PEG-Pd and at least 15 nm for PVP-Pd. Comparison with electrochemically determined true surface areas demonstrates rare coalescence of nanoparticles. Electrodes formed in PVP-containing solutions are found to exhibit enhanced electrocatalytic activity towards NO3- electroreduction at the potentials close to the reversible hydrogen electrode. (C) 2002 Elsevier Science Ltd. All rights reserved.