In the past decades, there has been an ongoing search for tailor-made active metal nanoparticles for the use as electrocatalysts. An upcoming versatile and green method for the synthesis of nanoparticles is electrodeposition. However, the state-of-the-art electrodeposited metal particle sizes are in the range of 50-200 sun. Production of high surface area metallic electrocatalysts with small particle sizes is a serious limitation of electrodeposition, i.e., the Gordian Knot. In this article, we present a novel and facile approach by combining electrodeposition with controlled cathodic corrosion to obtain tailor-made nanoparticles down to the single atom. Via controlled cathodic corrosion treatment, relatively big electrodeposited metal nanoparticles (Ag, Pt, Pd, Ni, etc.) are effectively broken down and evenly dispersed on the carbon electrode surface, without particle detachment. The same electrochemical phenomenon is also utilized for in-situ electrocatalysts reactivation, referred as redis-persion, of the degraded electrocatalysts. The two new concepts open new possibilities and applications for the electrodeposition as a metal nanoparticles production method and in-situ regeneration solutions for electrochemical energy conversion reactors like fuel cells and electrolyzers; as the two pillars of a near-future transition to sustainable energy.