Seaweed-derived KOH activated biocarbon for electrocatalytic oxygen reduction and supercapacitor applications

Seaweed blooms have become a serious worldwide environmental, economic and social problem. Reducing the cost of electrodes for electrochemical generation/storage systems is crucial for its commercialization. Ascophyllum nodosum grows abundantly in northern oceans, in this study, we evaluate A. nodosum derived chemically activated biocarbon (AKPH) with potassium hydroxide (KOH) as electrode material for oxygen reduction reaction and supercapacitors. Physical–chemical, morphological and electrochemical characterizations were performed. SEM micrographs revealed the morphology changes in AKPH due to KOH activation. AKPH nitrogen and sulfur contents were 0.80 and 5.62 (wt.%), respectively and it exhibited 1493 m² g⁻¹ surface area with an I_D/I_G intensity ratio of 1.34 ± 0.01. The electrochemical performance indicates a good performance when compared to commercial platinum, with an onset and half-wave potential of 0.878 and 0.75 V vs. RHE, respectively; and a current density of 5.2 mA cm⁻². AKPH exhibited a capacitance of 207.3 F g⁻¹ at 0.5 A g⁻¹ and good stability after 2500 cycles at 5 A g⁻¹ with a retention capability of 92.3%. This performance turns seaweed in a promising way to synthesize materials for applications in energy conversion and storage field.