Graphene Oxide-Based Non Precious Metal Catalysts for Oxygen Reduction Reaction with Improved Selectivity and Performance

Abstract

Due to the high cost of Pt-based catalysts for the anode and the cathode of polymer electrolyte fuel cells (PEFCs), their commercialization and distribution have been limited. Non-precious metal catalysts (NPMCs) with high activity and low peroxide yields [1, 2] represent a viable option for replacing the Pt-based catalysts for oxygen reduction reaction in the PEFC cathode. Graphene and graphene oxide-based catalysts have shown promising properties, such as good chemical stability and excellent conductivity, and they can be modified in a controllable manner by inducing functionalities [3]. However, the ORR activity of nitrogen-doped graphitic systems is lower than that of conventional nitrogen-doped mesoporous carbons. This is primarily due to fewer active sites on the basal plane than graphene edges and, secondly, due the re-stacking of n-doped graphitic sheets that forms an impermeable film, which limits the diffusion of reactants to the active sites. These key challenges have precluded the use of N-doped graphene-oxide catalysts for practical applications. In this presentation, we will show how the treatment of graphene oxide with solvents chosen based on Hansen’s solubility parameters, followed by nitrogen doping, results in the formation of active ORR catalysts [4]. Furthermore, we will use electrochemical treatment to enhance the four-electron selectivity of catalysts in oxygen reduction. Structural, chemical, and morphological information by X-ray techniques (XRD and XPS) will be presented, along with electron microscopy (SEM, TEM). The ORR activity graphene of oxide-based catalysts in both alkaline and acidic media, determined using a rotating ring-disk electrode (RRDE), will be presented. The results of this study are expected to aide in the synthesis of well performing graphitic ORR electrocatalysts with tunable activity and could lead in the future to better understanding of the mechanism ORR active site formation. Acknowledgement Financial support from the Los Alamos National Laboratory, Laboratory-Directed Research and Development (LDRD) is gratefully acknowledged.