Carbon Supported PtRu-Ni Ternary Nanoparticles with a PtRu Rich Shell Using a Polydopamine Protective Coating As CO Tolerant Electrocatalyst

Abstract

Carbon supported PtRu-Ni/C catalysts with a Ni-rich core structure are prepared through high temperature treatment of as-prepared polyol PtRu/C catalysts. It is well acknowledged that in conventional PtRu alloys, Ru prevents the adsorption of carbon monoxide on Pt surface via bifunctional mechanism. Also, the ligand effect is known to alter the electron structure of Pt for increased CO tolerance. In this work, the optimal Ni amount is determined for enhanced high resistance to carbon monoxide poisoning. The diffusion of Ni into the core of the catalysts is conducted by controlling the temperature during heat treatment. The as-prepared polyol PtRu/C catalysts have carbonized polydopamine layer on the surface, which prevents particle segregation during high temperature heat treatment. The carbon layer also partakes the role of transferring Ni particles into the core of the catalyst. When compared to using without protective coating method to directly fabricate PtRu-Ni/C catalysts, this method is far more superior. In general, Ni species on the surface is easily to be dissolved in acidic medium in PEMFC. But, PtRu-Ni/C with protective coating, in which Ni species is located inside the bulk of nanoparticles, would prevent it from dissolution in acidic medium while keeping the interaction between Ni and surface Pt.In this study, Energy-dispersive X-ray spectroscopic line scan profile confirm that the PtRu-Ni/C catalyst has a Ni-rich core and PtRu-rich shell structure. From polymer electrolyte membrane fuel cell tests using CO containing H2 gas, the core-shell structured PtRu-Ni/C alloy formed by protective coating method is demonstrated to have higher tolerance to CO poisoning than PtRu/C catalysts synthesized by polyol method.