Switch on ORR Performance of NiOx Supported Pd Nano-Islands via Optimized Pt-Loading Mediated Surface and Subsurface Configuration Controls

Yi-Jia Wu^1*, Dinesh Bhalothia¹, Che Yan¹, Tsan-Yao Chen¹

¹Department of Engineering and System Science, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Yi-Jia Wu, email:wuikea8586@gmail.com

Development of efficient nanocatalysts (NCs) with low noble-metal loading that accelerate sluggish oxygen reduction reaction (ORR) kinetics are highly desirable. In this study, nanocatalysts (NCs) comprising NiOx supported Pd nano-islands and sub-nanometer Pt clusters mask (NPP) is developed. By cross-referencing results of structural characterizations and electrochemical analysis, we demonstrated that the oxide structure can be suppressed accompanied with the increase of Ni intermix by decorating proper amount of Pt clusters mask in surface and thus boost the ORR performance of NPP NCs. In optimum case with a Pt loading of 9 wt.%, the Pt decorated Ni@Pd NC shows a mass activity of ~22.74-fold (1523.7 mA mg-1) and ~26.8-fold (671.5 mA mg-1) as compared to that of commercial Pt catalyst at 0.85 volt (vs. RHE) (67.1 mA mg-1) and 0.90 volt (vs. RHE) (24.5 mA mg-1). Such an optimization is attributed to a proper control of surface coverage and size of Pt clusters. It protects the surface form oxidation and thus leaving high density of reaction sites for oxygen adsorption in ORR. Further increasing the Pt contents results in a high density of nucleation sites and high extent of homoatomic clustering of Pt atoms in NiOx@Pd surface. Such a scenario reduces the surface coverage of Pt clusters, in this event, suppress the ORR activity of NPP NCs. The result obtained in this study is very intriguing and is an important clue for the development of next-generation ORR catalysts.

Keywords: oxygen reduction reaction, nanocatalysts, fuel cell, platinum, electrochemical