Programmable Exposure of Pt Active Facets for Efficient Oxygen Reduction
Pt-based materials are the state-of-the-art catalysts for oxygen reduction reaction (ORR), but their high cost and scarcity remain the major obstacles for large-scale applications in renewable energy industries. To produce efficient ORR catalysts with low Pt content, PtNi porous films (PFs) with sufficiently exposed Pt active sites were rationally designed through a programmable approach combining electrochemical bottom-up (electrodeposition) and topdown (anodization) processes. The unique dynamic oxygen-bubble template (DOBT) programmably controlled by square-wave potential was utilized to tune the catalyst morphology and expose Pt active facets in PtNi PFs. Here, the surface-bounded species such as hydroxyl anions (OH*, *=surface site) on the exposed PtNi PFs surfaces were adjusted by the applied anodic voltage, further affecting the dynamic oxygen (O 2 ) bubbles adsorption on Pt. As a result, PtNi PF with enriched Pt (111) facets (denoted as Pt 3.5% Ni PF) was obtained, showing prominent ORR activity with an onset potential of 0.92 V (vs. RHE) at an ultra-low Pt loading (0.015 mg cm -2 ). The adsorbed OHads coverage estimation shows fewer OHads on Pt 3.5% Ni PF than other PtNi PFs, indicating that enriched Pt (111) facets in the catalysts enable facilitated O 2 adsorption for oxygen reduction and thus leading to superior ORR activity