With the intensifying global need for alternative energy, there is strong interest in new approaches for generating and using energy efficiently, and for sustainably storing energy as chemical fuels. Efficient energy transformations involving chemical bonds rely on effective catalysts to lower reaction kinetic barriers. The increased variety of available structural and chemical configurations in vapor phase condensed nanoparticles has the potential for new and improved heterogeneous catalysts. Here we report on elemental and alloy nanoparticles formed via vapour phase condensation. The vapor phase source is a three-target magnetron sputter source operating into a relatively high-pressure inert gas environment. The sputtered atoms are cooled by collisions with the inert gas molecules, resulting in condensation into nanoparticles. By controlling the inert gas pressure and composition, the length of the condensation zone and other experimental variables the particle size distribution can be tuned. A quadrupole mass spectrometer is used to characterize the size distribution and select a size to impinge on the sample surface. We report on copper-silver alloy nanoparticles for the oxygen reduction reaction, and on rhenium nanoparticles incorporated into an electrode structure for electrochemical ammonia production. We discuss use of appropriate underlayers to facilitate particle adhesion in chemical environments. The effect of structure, size and composition on electrochemistry is explored.