Synthesis of uniform bulk nanoporous palladium with tunable structure

This work presents systematic investigations on the synthesis of hierarchical nanoporous Pd via electrochemical dealloying of CuPd alloys in sulfuric acid. The impact of electrode potential, dealloying temperature, and additional annealing on microstructure and morphology is explored. Dealloying Cu85Pd15 in 1M sulfuric acid at elevated temperature provides a facile strategy to produce bulk nanoporous Pd samples which are uniform, hierarchically nanoporous, and free of macro-scale cracks. The question “Why will one-step template-free dealloying yield a hierarchical and not unimodal nanoporous structure?” is discussed. The impact of passivation and of a percolating Cu-rich cluster on the pore structure is inspected. A structural instability concept for dealloying of dilute master alloys is preferred as the underlying mechanism. Nanoporous Pd with classical, unimodal pore structure and tunable ligament size ranging from 80 to 270 nm emerges when the as-prepared hierarchical nanoporous Pd is annealed. The material of this study may provide a model system that complements nanoporous Au for studies of bulk nanoscale metal networks as functional and structural materials.