Synergistic microbubble processing and tailored electrode fabrication of sustainable oil palm-derived carbon for superior supercapacitor performance

Porous carbon is a favoured electrode material for supercapacitors, valued for its high electrical conductivity, high specific surface area, thermal and chemical stability, and ease of hybridisation, yet its performance is often limited due to an improper pore structure. This study addresses this limitation by optimising the pore network structures of carbon electrodes derived from Thai oil palm waste. Utilising hydrothermal carbonisation (HTC) combined with a novel microbubble technique then fabricating into both free-standing electrodes (self-supporting) and substrate electrodes (requiring a supporting material such as a graphite sheet) to identify the optimal process. Free-standing electrodes, processed under optimal microbubble conditions (7C3P_R500), demonstrated significantly improved carbon particle distribution and ion transportation, leading to enhance electrochemical performance (3.6 F/g at 10 mV/s) compared to traditional sonication without microbubble process (2.7 F/g at 10 mV/s). Substrate electrodes (optimal condition 7C3PG_R200) exhibited superior electrochemical performance (66 F/g at 10 mV/s) by optimising electrode structure, presenting advantages in electrochemical performance and active material utilisation. Additionally, symmetric supercapacitors employing 7C3PG_R200 as electrodes achieved an energy density of 0.85 Wh/Kg and a power density of 1425 W/kg with capacitance retention remaining above 80% after 10000 cycles, attributed to the improved electrode pore structure and uniform porous carbon distribution. These findings suggest that as-synthesised porous carbon is particularly well-suited for fabricating into substrate electrodes and the microbubble synthesis offering a sustainable and economically viable solution for next-generation energy storage devices with reduced resistive losses and sustained high device efficiency. • Microbubble technique optimises pore architecture for better ion accessibility. • 7C3PG_R200 substrate electrodes achieved 66 F/g via tailored structures. • Symmetric devices reached 0.85 Wh/kg energy and 1425 W/kg power densities. • HTC-microbubble process offers a scalable and low-energy synthesis route.