Hollow nanoparticles made of a noble metal and a non-noble metal can be synthesized by a combination of galvanic replacement and the nanoscale Kirkendall effect. In these nanostructures, a metallic shell composed of individual nanocrystallites interconnected via grain boundaries surrounds a central cavity that is accessible to molecules through nanometre-sized pores. Moreover, because atomic vacancies enter the metal lattice during their formation, the surface of hollow metal nanoparticles is jagged both at the atomic and the nanometre scale. That gives them specific electrocatalytic properties, which are illustrated with reactions of increasing complexity (CO_ads monolayer electrooxidation, oxygen reduction reaction, methanol and ethanol electrooxidation) and rationalized with Density Functional Theory calculations.