Why Pt Survives but Pd Suffers From SO_x Poisoning?

Abstract

Pd is more prone to sulfation compared to Pt. Given the chemical similarity between Pt and Pd, the radical divide in their tendencies for sulfation remains a puzzle. We explain this intriguing difference using an extensive first-principles thermodynamics analysis and computed bulk and surface phase diagrams. In practically relevant temperatures and O2 and SO3 partial pressures, we find that Pt and Pd show significantly different tendencies for oxidation and sulfation. PdO formation is favored even at low oxygen chemical potential; however, PtO2 formation is not favorable in catalytically relevant conditions. Similarly, PdSO4, and adsorbed SO3 and oxygen species on clean and oxidized surfaces are highly favored, whereas PtSO4 formation does not occur at typical temperature and pressure conditions. Finally, several descriptors are identified that correlate to heightened sulfation tendencies, such as the critical O chemical potential for bulk oxide and surface oxide formation, chemical potentials O and SO3 for bulk sulfate formation, and SO3 binding strength on metal surface-oxide layers, which can be used to explore promising sulfur resistant catalysts.

Role of filler and its heterostructure on moisture sorption mechanisms in polyimide films

“…DFT computations showed that the (001) face has the highest binding affinity to water. Unlike other typical systems (for example, H 2 O on fcc metal surfaces 42 ), our results show that hydrogen bonding between H 2 O molecules on (002) surfaces leads to an increase in binding strength with increase in surface coverage. Finally, first principles thermodynamics calculations were used to construct phase diagrams for realistic temperature and pressure environments.…”

“…The represent the temperature and pressure dependent chemical potential term. Chemical potential of H 2 O can be calculated as: which contains the DFT computed energy of an isolated H 2 O molecule and chemical potential with temperature and pressure dependence (computation details can be found in refs 42 , 64 ).…”

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