Relationships between Atomic Level Surface Structure and Stability/Activity of Platinum Surface Atoms in Aqueous Environments

The development of alternative energy systems for the clean production, storage, and conversion of energy is strongly dependent on our ability to understand, at atomic molecular levels, the functional links between the activity and stability of electrochemical interfaces. Whereas structure activity relationships are rapidly evolving, the corresponding structure stability relationships are still missing. This is primarily because there is no adequate experimental approach capable of monitoring the stability of well-defined single crystals in situ. Here, by utilizing the power of inductively coupled plasma mass spectrometry (ICP-MS) connected to a stationary probe and coupling this technique to the rotating disk electrode method, it was possible to simultaneously measure the dissolution rates of surface atoms (as low as 0.4 pg cm(-2) s(-1)) and correlate them with the kinetic rates of electrochemical reactions in real time. Making use of this unique probe, it was possible to establish almost atom by atom structure-stability-activity relationships for platinum single crystals in both acidic and alkaline environments. We found that the degree of stability is strongly dependent on the coordination of surface atoms (less coordinated yields less stable), the nature of covalent and noncovalent interactions (i.e., adsorption of hydroxyl groups, oxygen atoms, and halide species vs interactions between hydrated Li cations and surface oxide), the thermodynamic driving force for Pt complexation (Pt ion speciation in solution), and the nature of the electrochemical reaction (the oxygen reduction/evolution and CO oxidation reactions). These findings open new opportunities for elucidating key fundamental descriptors that govern both activity and stability trends and will ultimately assist in the development of real energy conversion and storage systems.