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.