Thermodynamics of the formation of surface PtO2 stripes on Pt(111) in the absence of subsurface oxygen

• Published in: Physical chemistry chemical physics : PCCP 2020-05, Vol.22 (19), p.10634-10640
• Main Authors: Hanselman, Selwyn, McCrum, Ian T, Rost, Marcel J, Koper, Marc T M
• Format: Article
• Language: English
• Subjects: Computer simulation; Density functional theory; Energy of formation; Free energy; Heat of formation; Internal energy; Mathematical analysis; Oxidation; Platinum; Roughening; Thermodynamics
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c9cp05107d

This paper examines the thermodynamics of PtO2 stripes formed as intermediates of Pt(111) surface oxidation as a function of the degree of dilation parallel to the stripes, using density functional theory and atomistic thermodynamics. Internal energy calculations predict 7/8 and 8/9 stripe structures to dominate at standard temperature and pressure, which contain 7 or 8 elevated PtO2 units per 8 or 9 supporting surface Pt atoms, respectively. Moreover, we found a thermodynamic optimum with respect to mean in-stripe Pt–Pt spacing close to that of α-PtO2. Vibrational zero point energies, including bulk layer contributions, make a small but significant contribution to the stripe free energies, leading to the 6/7 stripe being most stable, although the 7/8 structure is still close in free energy. These findings correspond closely to experimental observations, providing insight into the driving force for oxide stripe formation and structure as the initial intermediate of platinum surface oxidation, and aiding our understanding of platinum catalysts and surface roughening under oxidative conditions.