Programmable Electrodeposition of Ptni Alloy Porous Film for Oxygen Reduction

Abstract

Oxygen reduction reaction (ORR) is a critical process in many emerging energy technologies, such as fuel cells and metal-air batteries, determining the energy conversion efficiency of devices.However, the complex electron transfer pathways involved in the oxygen-oxygen (O-O) bond cleavage makes ORR kinetically sluggish. Platinum (Pt)-based materials are the state-of-the-art ORR catalysts due to their proper surface electronic structures toward efficient cleavage of O-O bond. However, the high cost and limited natural availability of Pt severely hinder its large-scale commercial application for ORR. Even though many Pt-free catalysts have been claimed in recent years as alternatives to Pt, their ORR performances and production costs still can not really compete with Pt. Hence, it is of vital importance but very challenging to develop efficient ORR catalysts with low Pt loading. In this work, we used O2 bubbles as gaseous templates to fabricate PtNi nanoporous films with ultra-low Pt loading, which could be achieved through controlling oxygen evolution reaction (OER) during the programmable synthesis process. The rationally designed nanoporous PtNi catalysts have selectively exposed Pt (111) facets with ultra-low Pt loading (0.015 mg cm-2) for ORR. We discovered that the adsorbed O2 bubbles on the Pt surfaces act as protection agents, preventing Pt oxidation and dissolution. As a result, the enriched Pt (111) facets are preferentially exposed on the surface of PtNi PFs, showing superior ORR activity to other low-Pt catalysts.