Facile preparation of polybenzoxazine-based carbon microspheres with nitrogen functionalities: Effects of mixed solvents
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RESEARCH ARTICLE
Facile preparation of polybenzoxazine-based carbon microspheres with nitrogen functionalities: Effects of mixed solvents on pore structure and supercapacitive performance Uthen Thubsuang (✉)1, Suphawadee Chotirut1, Apisit Thongnok1, Archw Promraksa1, Mudtorlep Nisoa2, Nicharat Manmuanpom3,4, Sujitra Wongkasemjit3,4, Thanyalak Chaisuwan3,4 1 School of Engineering and Technology, Walailak University, Nakhon Si Thammarat 80160, Thailand 2 School of Science, Walailak University, Nakhon Si Thammarat 80160, Thailand 3 The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand 4 Center of Excellence on Petrochemical and Materials Technology, Bangkok 10330, Thailand
© Higher Education Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this study, polybenzoxazine (PBZ)-based carbon microspheres were prepared via a facile method using a mixture of formaldehyde (F) and dimethylformamide (DMF) as the solvent. The PBZ microspheres were successfully obtained at the F/DMF weight ratios of 0.4 and 0.6. These microspheres exhibited high nitrogen contents after carbonization. The microstructures of all the samples showed an amorphous phase and a partial graphitic phase. The porous carbon with the F/DMF ratio of 0.4 showed significantly higher specific capacitance (275.1 F∙g‒1) than the reference carbon (198.9 F∙g‒1) at 0.05 A∙g‒1. This can be attributed to the synergistic electrical double-layer capacitor and pseudo-capacitor behaviors of the porous carbon with the F/DMF ratio of 0.4. The presence of nitrogen/oxygen functionalities induced pseudo-capacitance in the microspheres, and hence increased their total specific capacitance. After activation with CO2, the specific surface area of the carbon microspheres with the F/DMF ratio of 0.4 increased from 349 to 859 m2∙g‒1 and the specific capacitance increased to 424.7 F∙g‒1. This value is approximately two times higher than that of the reference carbon. The results indicated that the F/DMF ratio of 0.4 was suitable for preparing carbon microspheres with good supercapacitive performance. The nitrogen/oxygen functionalities and high specific surface area of the microspheres were responsible for their high capacitance. Keywords PBZ, carbon, porous materials, microsphere, supercapacitor
Received July 18, 2019; accepted September 10, 2019 E-mail: [email protected]
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Introduction
With the growing concerns on energy sustainability, cost, and environmental issues, renewable energy sources such as solar and wind energy have gained immense attention as clean alternatives to fossil fuels for power generation without CO2 emission. These renewable energy sources are expected to make a significant contribution to the world energy supply in the near future. However, the dependence of renewable energy sources on weather conditions such as the lack of sunlight in winter and during rainy season causes electrical energy shortages. This limitation can be overcome by developing electrical double-layer capacitors (EDLCs), which
