Studies on the Electrochemical Stability of Preferentially (100)‐Oriented Pt Prepared through Three Different Methods

The electrochemical stability of the Pt(100) surface is investigated by electrochemical methods and morphological and structural characterization. Preferentially (100)-oriented Pt is prepared by three different methods: use of water-in-oil microemulsions, electrodeposition and electrochemical faceting. The loss of the Pt(100) sites particularly the wide (100) surface domains during the potential cycling is confirmed by the hydrogen-desorption profile in H2SO4 solution, the decreasing specific activity for ammonia electro-oxidation and the decreasing proportion of Pt(100) sites as characterized by irreversible Ge adsorption. This is consistent with TEM observations that show that the well-defined cubic Pt nanocubes change to a polycrystalline structure, whereas the sharp tips of electrodeposited Pt nanoparticles become rounded/blunt or disappear after 300 potential cycles. Noticeably, the bulk Pt disk electrode treated by electrochemical faceting exhibits a much higher electrochemical stability compared to preferentially (100)-oriented Pt nanoparticles. The high electrochemical stability is probably related to its preparation procedure, which involves high-frequency selective electrodissolution/electrodeposition of Pt atoms coupled to the periodic adsorption/desorption of oxygen-containing species and hydrogen adatoms.