The “cathodic corrosion” method for nanoparticle synthesis has been used to produce Pt nano-crystals with a preferential (100) orientation. These particles are surfactant-free and electrochemically clean, featuring a significant percentage of (100) terrace sites, as confirmed by electrochemical characterization tests to establish the amount of (100) sites: blank voltammetry in H2SO4, adsorbed CO stripping, and Ge irreversible adsorption. The high catalytic activity of these preferentially oriented particles is confirmed for reactions preferring (100) sites, such as dimethyl ether oxidation, ammonia oxidation, and nitrite reduction in alkaline media. In the case of nitrite reduction it is demonstrated that, similarly to (100) terraces of a well-ordered Pt single crystal electrode, the (100) facets of the nano-crystals can steer the reaction towards the selective formation of N2. The use of an inexpensive preparation method to obtain nano-electrocatalysts that can perform selective electrocatalytic reactions such as ammonia oxidation and nitrite reduction, can pave the way for a new generation of practical catalysts for environmental and energy purposes.