Hierarchical carbon nanospheres-based electrodes for low-temperature pseudocapacitors

Hierarchical porous carbon nanospheres (H-PC) with a large micropore-dominated structure has been designed and synthesized, demonstrating superior ion diffusion and charge transfer efficiency compared to carbon electrodes prepared by either soft or hard template methods. H-PC was used to fabricate pseudocapacitive electrodes by electrochemical deposition of anthraquinone-2-sulfonic acid (AQS) onto the screen-printed H-PC electrodes (H-PC@AQS). The AQS molecules which anchored in the inner pore space of H-PC relied on the highly conductive H-PC walls as electron conduction channels for efficient redox charge generation, while the large micropores allowed efficient mass diffusion of the electrolyte and prevented the loss of AQS during the electrochemical process. H-PC@AQS has a specific areal energy of 25.7 μWh cm⁻², 207.9 % higher than the 12.4 μWh cm⁻² for H-PC. H-PC@AQS has a specific capacitance of 185.4 mF cm⁻² at room temperature and 89.1 mF cm⁻² at -50 °C, highlighting its potential as a high-performance pseudocapacitor for low-temperature operations. The incorporation of AQS into the micropores of H-PC not only improved the overall capacitance of carbon but also ensured stable performance across a wide temperature range.