Macadamia shells were carbonized at 600°C and KOH-activated at 800°C with carbon:KOH ratios of 1:1 to 1:3. Activation raised surface area from 325 to 1,362 m2/g, producing mainly micropores with partial mesoporosity. The 1:3 material reached 170 F/g at 1 A/g in three-electrode 6 M KOH and behaved mainly as an electric double-layer capacitor. A symmetric coin cell delivered 5.4 Wh/kg and 2,500 W/kg and remained stable for 10,000 cycles at 3 A/g.
Key findings
- Surface area rose 325 to 1,362 m2/g; 1:3 reached 170 F/g; EDLC dominated; coin cell delivered 5.4 Wh/kg and 2,500 W/kg; 10,000-cycle stability was reported.
Why this matters globally
The approach valorizes agricultural waste and diversifies electrode feedstocks in macadamia-producing regions if KOH recovery, washing and batch consistency are controlled.
Thai researcher contribution
Nattapat Chaiammart, Parinya Chakartnarodom, Apiluck Eiad-ua and G. Panomsuwan of Kasetsart and KMITL form the Thai biomass-carbon and energy-storage team.
Limitations to consider
A 1:3 KOH ratio is chemically intensive and washing wastewater and carbon yield belong in LCA. Three-electrode metrics exceed device performance; mass loading, thickness, voltage, ESR, self-discharge and retention percentage are absent. Energy density may use active mass and remains below batteries.