QCM-D studies of polypyrrole influence on structure stabilization of β phase of Ni(OH)2 nanoparticles during electrochemical cycling

Pure β badly crystallized, β_bc-Ni(OH)₂, and hybrid β_bc-Ni(OH)₂/polypyrrole nanoparticles (NPs) were synthesized and immobilized by electrophoretic deposition. The influence of polypyrrole (Ppy) on the structural stability with cycling was evaluated by Quartz Crystal Microbalance with Dissipation. The results show that Ppy stabilizes the NP structure avoiding stress features provoked by the formation of γ-NiOOH. Ppy remains oxidized during the entire process and, as it is doped with a big counter anion such as dodecylbenzenesulfonate (DBS⁻) which is not removed during cycling, avoids volumetric changes of Ni(OH)₂ leading to higher cyclability.