The sluggish kinetics of the oxygen reduction reaction (ORR) is one of the main drawbacks towards the commercialization of proton exchange membrane fuel cells (PEMFCs) and anion exchange membrane fuel cells (AEMFCs). State-of-the-art ORR electrocatalysts (ECs) consist of carbon-supported Pt nanoparticles. Nonetheless, the insufficient durability of these ECs and the low abundance of platinum constitute some of the major challenges for large-scale commercialization of PEMFC and AEMFC technology [1]. Thus, the development of very efficient cathodic electrocatalysts is necessary to substitute the Pt/C “state-of-the-art” ECs. In this work a group of hierarchical “core-shell” ECs for the ORR is synthesized following an innovative preparation protocol [2]. The “shell” consists of a carbon nitride (CN) matrix coordinating bimetallic PtNix, AuNix and FeSnx nanoparticles. The “core” consist of graphene nanoplatelets [3]. Inductively-coupled plasma atomic emission spectroscopy (ICP-AES) and microanalysis are carried out to evaluate the chemical composition of the ECs; Scanning Electron Microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) are used for the inspection of the morphology; powder X-ray diffraction (XRD) is adopted to study the structure of the ECs. Cyclic voltammetry with the thin-film rotating ring-disk electrode (CV-TF-RRDE) is used to determine the ORR performance and to study the reaction mechanism. The analysis of the chemical composition of the ECs reveals that N functionalities are bonded in the CN “shell” matrix covering the “cores” of graphene nanoplatelets. An increase of the pyrolysis temperature from 600 to 900°C improves the graphitization degree of the CN “shell” and facilitates the alloying process of the bimetallic metal nanoparticles of the ECs. Accordingly, ohmic drops of materials are reduced and the ORR activity is significantly improved. References [1] R. Othman, A. L. Dicks, Z. Zhu, Int. J. Hydrogen Energy, 37 (2012) 357-372. [2] V. Di Noto, E. Negro, F. Bertasi et al., Patent application 102015000055603. [3] V. Di Noto, E. Negro, S. Polizzi et al., ChemSusChem., 5 (2012) 2451–2459.
Hierarchical graphene-supported PtNix, AuNix and FeSnx “core-shell” carbon nitride electrocatalysts for the oxygen reduction reaction
Angeloclaudio Nale;Enrico Negro;Yannick Herve Bang;Keti Vezzù;Federico Bertasi;Chuanyu Sun;Graeme Nawn;Gioele Pagot;Giuseppe Pace;V. Di Noto
2017
Abstract
The sluggish kinetics of the oxygen reduction reaction (ORR) is one of the main drawbacks towards the commercialization of proton exchange membrane fuel cells (PEMFCs) and anion exchange membrane fuel cells (AEMFCs). State-of-the-art ORR electrocatalysts (ECs) consist of carbon-supported Pt nanoparticles. Nonetheless, the insufficient durability of these ECs and the low abundance of platinum constitute some of the major challenges for large-scale commercialization of PEMFC and AEMFC technology [1]. Thus, the development of very efficient cathodic electrocatalysts is necessary to substitute the Pt/C “state-of-the-art” ECs. In this work a group of hierarchical “core-shell” ECs for the ORR is synthesized following an innovative preparation protocol [2]. The “shell” consists of a carbon nitride (CN) matrix coordinating bimetallic PtNix, AuNix and FeSnx nanoparticles. The “core” consist of graphene nanoplatelets [3]. Inductively-coupled plasma atomic emission spectroscopy (ICP-AES) and microanalysis are carried out to evaluate the chemical composition of the ECs; Scanning Electron Microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) are used for the inspection of the morphology; powder X-ray diffraction (XRD) is adopted to study the structure of the ECs. Cyclic voltammetry with the thin-film rotating ring-disk electrode (CV-TF-RRDE) is used to determine the ORR performance and to study the reaction mechanism. The analysis of the chemical composition of the ECs reveals that N functionalities are bonded in the CN “shell” matrix covering the “cores” of graphene nanoplatelets. An increase of the pyrolysis temperature from 600 to 900°C improves the graphitization degree of the CN “shell” and facilitates the alloying process of the bimetallic metal nanoparticles of the ECs. Accordingly, ohmic drops of materials are reduced and the ORR activity is significantly improved. References [1] R. Othman, A. L. Dicks, Z. Zhu, Int. J. Hydrogen Energy, 37 (2012) 357-372. [2] V. Di Noto, E. Negro, F. Bertasi et al., Patent application 102015000055603. [3] V. Di Noto, E. Negro, S. Polizzi et al., ChemSusChem., 5 (2012) 2451–2459.
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