Oxygen Diffusion in Platinum Electrodes: A Molecular Dynamics Study of the Role of Extended Defects

AF Zurhelle and W Stehling and R Waser and RA De Souza and S Menzel, ADVANCED MATERIALS INTERFACES, 9, 2101257 (2022).

DOI: 10.1002/admi.202101257

Platinum serves as a model electrode in solid-state electrochemistry and as the inert electrode in redox-based resistive random-access memory (ReRAM) technology. Experimental work has proposed that oxygen may diffuse faster along platinum's extended defects, but quantitative, unambiguous transport data do not exist. In this study, the diffusion of oxygen atoms in crystalline platinum and along its extended defects is studied as a function of temperature by means of molecular dynamics (MD) simulations with the ReaxFF interatomic potentials. The MD simulations indicate that platinum vacancies trap oxygen atoms, inhibiting their diffusion through the platinum lattice and leading to a high activation enthalpy of diffusion of around 3 eV. This picture of trapping is supported by static density-functional-theory calculations. MD simulations of selected dislocations and selected grain boundaries indicate that oxygen diffusion is much faster along these extended defects than through the Pt lattice at temperatures below 1400 K, exhibiting a much lower activation enthalpy of approximate to 0.7 eV for all extended defects examined. Producing specific electrode microstructures with controlled densities and types of extended defects thus offers a new avenue to improve the performance of ReRAM devices and to prevent device failure.

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