(560ch) Devisable Bottom-up/ Top-Down Process Directed Facet-Engineered Pt Ni Porous Films As Efficient Oxygen Reduction Electrocatalysts

As the state-of-the-art catalysts for oxygen reduction reaction (ORR), the high cost and scarcity of Pt-based materials remain the major obstacles for their large-scale application in renewable energy industries. To produce efficient Pt-based ORR catalysts with low Pt content, a series of PtNi porous films (PFs) with abundant and facet-selectively exposed Pt active facets were rationally designed. The unique dynamic oxygen-bubble template (DOBT) formed through square-wave potential was utilized in order to realize the control of morphology and exposed Pt crystal planes in PtNi PFs. The generation and adsorption of hydroxyl species (OH_ads) on Pt centers can be tuned by the applied anodic voltage, which can affect the oxygen bubbles adsorption on Pt in DOBT. As a result, a (111) facet enriched PtNi PF (donated as Pt_3.5%Ni PF) was obtained and it shows prominent ORR activity with an onset potential of 0.94V and a limiting current of 5.3 mA cm^-2 _­at an extreme low Pt loading (0.015 mg cm^-2). The OH_ads coverage evaluation on PtNi PFs surfaces indicates that less OH^- are adsorbed on Pt_3.5%Ni PF as the existence of rich (111) facets, providing more active sites for initial O₂ adsorption for ORR process, and thus showing superior ORR activity.