Electrochemical Properties of Biobased Carbon Aerogels Decorated with Graphene Dots Synthesized from Biochar

Bony Thomas,Alberto Vomiero,Mohini Sain,Kristiina Oksman,Anton Landström,Gejo George,Isabella Concina,Shiyu Geng

doi:10.1021/acsaelm.1c00487

Abstract

Carbon aerogels prepared from low-cost renewable resources are promising electrode materials for future energy storage applications. However, their electrochemical properties must be significantly improved to match the commercially used high-carbon petroleum products. This paper presents a facile method for the green synthesis of carbon aerogels (CAs) from lignocellulosic materials and graphene dots (GDs) from commercially available biochar. The produced carbon aerogels exhibited a hierarchical porous structure, which facilitates energy storage by forming an electrical double-layer capacitance. Surprisingly, the electrochemical analyses of the GD-doped carbon aerogels revealed that in comparison to pristine carbon aerogels, the surface doping of GDs enhanced the electrochemical performance of carbon aerogels, which can be attributed to the combined effect from both double-layer capacitance and pseudocapacitance. Herein, we designed and demonstrated the efficacy of a supercapacitor device using our green carbon electrode as a sustainable option. These green carbon aerogels have opened a window for their practical use in designing sustainable energy storage devices.

Highlights

The deteriorating global environment and critical energy issues have led to the search for new energy materials/devices with excellent storage and power/energy density, which has been a hot topic in the past few years.[1−3] Supercapacitors are energy storage devices that consist of electrochemical double-layer capacitors (EDLCs) and pseudocapacitors.[4]
Carbon aerogels prepared from lignocellulosic precursors by ice-templating and freeze-drying followed by carbonization were incorporated with graphene dots (GDs), which can be used as supercapacitor electrodes
Novel GDs ranging in size from 5 to 15 nm were successfully synthesized from bio-derived carbon by oxidative acid treatment involving sulfuric and nitric acids

Summary

■ INTRODUCTION

The deteriorating global environment and critical energy issues have led to the search for new energy materials/devices with excellent storage and power/energy density, which has been a hot topic in the past few years.[1−3] Supercapacitors are energy storage devices that consist of electrochemical double-layer capacitors (EDLCs) and pseudocapacitors.[4]. A TGA Q500 analyzer (TA Instruments, New Castle, DE) was used to analyze the thermal properties of both the precursor biochar and the GDs. A nitrogen atmosphere was used during the analysis in a temperature range of 25−900 °C at a heating rate of 10 °C min−1. Samples were prepared by carefully peeling the outer surface with tape so that the microstructure of the carbon aerogels would be retained for a detailed analysis Images from both the cross section and longitudinal section were recorded. Elemental analysis using the SEM−energydispersive X-ray spectroscopy (EDX) data of the carbon aerogels was conducted using a scanning electron microscope (JSM-IT300, Jeol, Tokyo, Japan) equipped with a silicon drift detector (Oxford XMaxN, 50 mm[2], Oxford Instruments, Abingdon, U.K.).

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES