Metallic actuators have attracted a great deal of attention owing to their potential advantages over piezoelectric ceramics and conducting polymers. Here, we report different electrochemical actuation behaviors of bulk nanoporous palladium (np-Pd) fabricated by dealloying in acid (0.5 M H2SO4) and alkaline (1.0 M KOH) solutions. In the 1.0 M KOH solution, the reversible expansion/contraction of np-Pd well responds to the adsorption/desorption of involved species (H and OH). In the 0.5 M H2SO4 solution, only continuous contraction can be observed in the potential region involving the H-adsorption/desorption, but the reversible strain appears in the potential region related to the OH-adsorption/desorption. Moreover, the surface stress-charge coefficient (xi) exhibits inverse signs associated with the H-adsorption (absorption)/desorption and OH-adsorption/desorption in the alkaline solution. More importantly, the reversible strain amplitude of np-Pd can be regulated by changing the potential scan rate or by being stimulated in different electrolytes. (C) 2016 Elsevier Ltd. All rights reserved.