A Synthetic Route for the Preparation of PtRu-Ni Core-Shell Nanoparticles Using Polydopmaine Protective Coating for a 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 of Ni is known to alter the electron structure of Pt for increased methanol oxidation reaction (MOR). In this work, the optimal Ni amount is determined for enhanced MOR and 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 the polyol method to directly fabricate PtRu-Ni/C catalysts, this method is far more superior. Because Ni has a very low reducing power, most of it is lost during polyol process, and the final product has an extremely low Ni content. In this study, Energy-dispersive X-ray spectroscopic line scan profile and X-ray photoelectron spectroscopic analysis confirm that the PtRu-Ni/C catalyst has a Ni-rich core and PtRu-rich shell structure. From Cyclic voltammograms for methanol oxidation and polymer electrolyte membrane fuel cell tests using CO containing H2 gas, the core-shell structured PtRu-Ni/C alloy formed by high-temperature annealing is demonstrated to have higher tolerance to CO poisoning than PtRu/C catalysts synthesized by co-deposition via the polyol method.