Facilely synthesized nitrogen-doped reduced graphene oxide functionalized with copper ions as electrocatalyst for oxygen reduction

Nadia Garino,Angelica Chiodoni,Adriano Sacco,Michele Re Fiorentin,Juqin Zeng,Damien Salomon,Micaela Castellino,Francesca Risplendi,Katarzyna Bejtka,Candido F Pirri,Giancarlo Cicero,Jaime Segura-Ruiz

doi:10.1038/s41699-020-00185-x

Abstract

Nitrogen-doped reduced graphene oxide is successfully synthesized and functionalized with hydroxylated copper ions via one-pot microwave-assisted route. The presence of cationic Cu coordinated to the graphene layer is fully elucidated through a set of experimental characterizations and theoretical calculations. Thanks to the presence of these hydroxyl-coordinated Cu2+ active sites, the proposed material shows good electrocatalytic performance for the oxygen reduction reaction, as evidenced by an electron transfer number of almost 4 and by high onset and half-wave potentials of 0.91 V and 0.78 V vs. the reversible hydrogen electrode, respectively. In addition, the N-doped Cu-functionalized graphene displays a superior current retention with respect to a commercial Pt/C catalyst during the stability test, implying its potential implementation in high-performance fuel cells and metal-air batteries.

Highlights

To date, several efficient and smart technologies for energy conversion and storage are emerging as suitable strategies to build a green and sustainable future
Bright field transmission electron microscopy (TEM) (BFTEM) (Fig. 1c) and scanning TEM for the N 1s peak, we achieved the (STEM) (Fig. 1d, e) images confirm the good quality of the same conclusion obtained for the C 1s peak: no distortions are obtained reduced graphene oxide (rGO), and at the same time show that no copper oxide visible in the curves of the two samples
The selected area procedure applied to the high resolution (HR) spectra of both N-rGO and Cu-N-rGO, electron diffraction pattern, shown in Fig. 1f, presents a well- we obtained two components that can be assigned to N atoms defined spot pattern, composed of elongated bright spots in a implanted in the graphene lattice, one is attributed to pyrrolic-like hexagonal configuration

Summary

Introduction

Several efficient and smart technologies for energy conversion and storage are emerging as suitable strategies to build a green and sustainable future. Fuel cells[1,2] and metal-air batteries[3,4] attract particular worldwide interest, due to their high energy density, enabling an increasing driving autonomy in electric vehicles, to be comparable to that of gasoline-supplied vehicles, and supporting the development of small advanced portable electronic devices as well as auxiliary power units[5]. Both these electrochemical devices suffer from kinetically sluggish oxygen reduction reaction (ORR) at the oxygen/air cathode[6,7]. Graphene materials with binary, ternary and quaternary doping of various heteroatoms were widely investigated as ORR catalysts, such as boron/nitrogen-doped[24], nitrogen/sulfur-doped[25], nitrogen/phosphorous-doped[26,27], nitrogen/boron/phosphorous-doped[28] and boron/nitrogen/phosphorus/ sulfur-doped graphene[29]

Methods

Results

Conclusion