One-step, low temperature synthesis of reduced graphene oxide decorated with ZnO nanocrystals using galvanized iron steel scrap

R V Tolentino-Hernandez,E Jimenez-Melero,F Caballero-Briones,F J Espinosa-Faller,C Guarneros-Aguilar

doi:10.1088/2053-1591/ac0c9c

Abstract

Production of a ZnO–rGO composite, using a novel one-pot method consisting in continuously flowing argon into a GO aqueous suspension heated at 80 °C, in the presence of galvanized iron steel scrap is presented. FTIR shows the complete disappearance of GO functional groups and only the C=C band remained, indicating extensive GO reduction. Raman spectra indicated sp2 character increase after reaction and the presence of the E2h mode of ZnO. SEM showed submicron crystals identified by XRD as ZnO in the hexagonal phase, while TEM images indicate ZnO nanoparticles decorate mainly the rGO borders. Optical band gap of 3.5 eV corresponding to ZnO, and optical transitions at 4.1 and 5.5 eV related with n → π and π → π* were observed. Electrochemical characterization by cyclic voltammetry shows an specific capacitance of 4.7 F g−1 at a scan rate of 5 mVs−1, which drops to ca. 0.8 F g−1 at 200 mVs−1. By electrochemical impedance spectroscopy, the relaxation time was ca. 5 ms. The proposed mechanism for the materials‘ synthesis includes Zn dissolution from scrap, galvanic displacement of oxygen moieties at the GO sheet, Zn deposition onto the carbon surface, and further oxidation and growth of ZnO nanocrystals.

Highlights

Graphene oxide (GO) and reduced graphene oxide have been attractive in the development of new materials for technological applications as optoelectronic devices [1,2,3], chemical sensors [4], photovoltaic materials [5], energy storage [6] and composite materials [7, 8] due to its excellent optoelectronic, mechanical, thermal, and electrical properties
In the present contribution we describe an almost serendipitous finding: during the pursue for GO reduction at low temperature (80 °C) using galvanized iron steel scrap as reducing agent in the presence of Ar bubbling, reduced graphene oxide decorated with high quality ZnO crystals was obtained after only 1 h of reaction
In the ZnO–reduced graphene oxide (rGO) spectra, all the bands related with oxygen groups disappeared and only the bands of the graphene skeleton (C=C and C–C) are observed at 1560 and 970 cm−1 respectively, indicating a higher reduction degree, compared to the works of Mei [12] and Liu [13]

Summary

June 2021

R V Tolentino-Hernandez , E Jimenez-Melero, F J Espinosa-Faller , C Guarneros-Aguilar and F Caballero-Briones1,∗. FTIR shows the complete disappearance of GO functional groups and only the C=C band remained, indicating extensive GO reduction. Raman spectra indicated sp character increase after reaction and the presence of the E2h mode of ZnO. SEM showed submicron crystals identified by XRD as ZnO in the hexagonal phase, while TEM images indicate ZnO nanoparticles decorate mainly the rGO borders. Electrochemical characterization by cyclic voltammetry shows an specific capacitance of 4.7 F g−1 at a scan rate of 5 mVs−1, which drops to ca. The proposed mechanism for the materials‘ synthesis includes Zn dissolution from scrap, galvanic displacement of oxygen moieties at the GO sheet, Zn deposition onto the carbon surface, and further oxidation and growth of ZnO nanocrystals

Introduction

Experimental details

Results and discussion

Conclusions

Conflicts of interest