Highly Dispersed Carbon Supported Pdnimo Core with Pt Monolayer Shell Electrocatalysts for Oxygen Reduction Reaction

Abstract

Platinum (Pt/C) and its alloys are still the dominant catalyst material for polymer electrolyte membrane fuel cell and are not always stable under conditions of PEMC operation.1 It still has some draw backs which include its high cost, catalyst poisoning, and degradation due to dissolution and aggregation. These issues have been recognized as major concerns that must be resolved prior to commercialization of PEMFC. Due to these problems researchers in the field of electrocatalysts are faced with the challenging task of increasing the precious metal utilization (to enhance intrinsic activity, decrease loading, etc). Therefore, the development of low-cost, durable, and high-performance material substitute to the current Pt/C electrocatalysts can accelerate commercialization of fuel cells (FCs) as an alternative power source. In this study, we report a rapid synthetic approach for PdNiMo/C nanostructure fabrication on carbon support (i.e. activated carbon and carbon nanotube), made by sonolysis enhanced with ionic liquids (ILs). This technique combines the supramolecular chemistry between organometallic precursors, ionic liquids/carbon substrate, synthesis parameters, green chemistry techniques and interfacial engineering, for controlling the size and amount of uniformly dispersed metal nanoparticles (MNPs) without the addition of external reducing agents, surfactants or capping agents.2-4 The oxygen reduction reaction properties of the well-defined nanomaterial is further improved by using a single layer of Platinum monolayer (PtML) developed by Dr R. Adzic to maximize its activity at the oxygen cathode of Fuel Cells.5,6 The PtML shell /(Palladium-Nickel-Molybdenum-PdNiMo/C) ternary core electrocatalysts was evaluated for the oxygen reduction reaction (ORR) in acid media by electrochemical techniques.The electrocatalysts were characterized by high resolution transmission electron microscopy, (HRTEM),EELS, XANES and EXAFS. The modified electrocatalysts showed enhanced activity and better durability than Pt/C against potential cycling tests. References (1) Manthriram, A; Murugan, A. V.; Sarkar, A.; Muraliganth, T. Nanostructured electrode materials for electrochemical energy storage and conversion. Energy & Environment Science, 2008, 1, 621-638 (2) Suslick, K.S.; Hyeon, T.; Fang, M.; Nanostructured Materials Generated by High-Intensiry Ultrasound: Sonochemical Synthesis and Catalytic Studies. Chemical Mater. 1996, 8, 2172-2179. (3) Mizukoshi, Y.; Fujimoto, T.; Nagata, Y.; Oshima, R.; Maeda,Y. Characterization and Catalytic Avtivity of Core-Shell structured Gold/Palladium BimetallicNanoparticles Synthesized by the Sonochemical method. Journal of Physical Chemistry, B 2000, 104, 6028-6032. (4) Okoli,C.; Kuttiyiel, K.; Cole, J.; McCutchen,J; Tawfik,H; Adzic,R.; Mahajan,D. Solvent effect in sonochemical synthesis of metal-alloy nanoparticles for use as electrocatalysts. Ultrasonics Sonochemistry 2018, 41, 427-434. (5) R.R. Adzic, J. Zhang, K. Sasaki, M.B. Vukmirovic, M. Shao, J.X. Wang, A.U. Nilekar,M. Mavrikakis, J.A. Valerio, F. Uribe, Platinum monolayer fuel cell electrocata-lysts, Topics in Catalysis 2007, 46, 249. (6) J.L. Zhang, M.B. Vukmirovic, Y. Xu, M. Mavrikakis, R.R. Adzic, Controlling the catalytic activity of platinum-monolayer electrocatalysts for oxygen reduction with different substrates, Angewandte Chemie-International Edition 2005, 44, 2132.