Platinum single atom electrocatalysts draw extensive attention because of its outstanding catalytic efficiency compared to the metallic platinum catalyst. Tuning the loading material varies the performance of the single-atom electrocatalysts broadly. Therefore, understanding the correlation between the activity and the electronic structure of the Pt atoms at the reaction site is essential to design the new platinum single-atom electrocatalysts. Moreover, the correlation contributes to interdisciplinary connections between complex chemistry and surface chemistry. These connections can help overcoming the inaccuracy and less efficiency of the first-principles methodologies that are applicable on simulating electrocatalysis on metal electrodes under a complex environment. In this work, DFT and computational hydrogen electrode approach are used to investigate the elementary steps of oxygen reduction reaction (ORR) on two single-atom platinum electrodes including PAH loaded Pt (Pt-PAH) and graphene loaded Pt (Pt-graphene) and one metallic electrode, Pt(111) surface. Preliminary results show that the reaction free energy of the elementary steps to form O<sub>2</sub> and O* increases following the sequence of Pt-PAH, Pt-Graphene and Pt(111), while that decreases for the formation of OH*. These sequences match the increase of charge on Pt atoms from Pt-PAH (+0.88) to Pt-graphene (+0.82) and then Pt(111) (-0.04). Such a correlation indicates an analogy in the reaction mechanism on both single atom electrodes and metallic electrodes. The reaction free energies of the OOH formation differ less than 0.15 eV among all the catalysts, which indicates its irrelevance to the catalyst. These analogies can be explained as that the reaction is localized and the way that intermediates bind to Pt atoms are similar. Detailed analysis of the electronic structure will be carried out in the future. Our results will not only be applicable in predicting the performance of the new Pt single-atom catalysts, but also be important in circumventing complexities in modeling reactions on bulk electrodes under solution environments and accurately and efficiently obtaining their kinetic parameters.

First-principles investigations of the analogy in the oxygen reduction reactions on both platinum single-atomic electrocatalysts and Pt(111) surfaces

ACS Spring Meeting 2021

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