Abstract
The renewable biomass material obtained from rice husk, a low-cost agricultural waste, was used as a precursor to synthesize a highly porous graphene-based carbon as electrode material for supercapacitors. Activated graphene-based carbon (AGC) was obtained by a two-step chemical procedure and exhibited a very high specific surface area (SSA) of 3292 m2 g−1. The surface morphology of the synthesized materials was studied using scanning and transmission electron microscopy (SEM, TEM). Furthermore, the AGC was modified with nickel hydroxide Ni(OH)2 through a simple chemical precipitation method. It was found that the most significant increase in capacitance could be reached with Ni(OH)2 loadings of around 9 wt.%. The measured specific capacitance of the pure AGC supercapacitor electrodes was 236 F g−1, whereas electrodes from the material modified with 9 wt.% Ni(OH)2 showed a specific capacitance of up to 300 F g−1 at a current density of 50 mA g−1. The increase in specific capacitance achieved due to chemical modification was, therefore 27%.
Highlights
Due to various problems such as air quality and climate change, the world’s energy system is shifting from a fossil fuel-driven economy to renewable energy sources
Porous carbon or so-called activated carbon was successfully synthesized by using rice husk as a renewable biomass waste
The galvanostatic charge-discharge (GCD) data showed a specific capacitance of 236 F g−1 at a current density of 50 mA g−1
Summary
Due to various problems such as air quality and climate change, the world’s energy system is shifting from a fossil fuel-driven economy to renewable energy sources. With a growing share of renewable energy sources in the electricity grid, an increased amount of storage devices will be needed. Electrical energy storage devices must fulfil a wide variety of very different requirements, for example, securing grid stability and power quality in microsecond intervals for long-time storage of significant energy amounts for seasonal energy compensation [1]. Supercapacitors are promising devices for short-term energy storage due to their long-cycle life and fast charge–discharge processes [2]. Their characteristic properties make them suitable for Energies 2020, 13, 4943; doi:10.3390/en13184943 www.mdpi.com/journal/energies
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