In-situ O/N-heteroatom enriched activated carbon by sustainable thermal transformation of waste coffee grounds for supercapacitor material

By leveraging the sustainable selective thermal transformation, the waste coffee grounds could be converted to a hetero oxygen/nitrogen atom induced meso-microporous activated carbon without using any pore-forming agent or dopant. N originates from the natural protein and caffeine of coffee and is implanted into the activated carbon in situ. The activated carbon gains a decent specific surface area of 580 m2/g with a meso-microporous structure where the average pore diameter is ∼2.5 nm. The findings reveal the benefits of an in-situ nitrogen/oxygen hetero-atom enrichment and porous structure of activated carbon materials via thermal activation on energy storage applications. The activated carbon demonstrates the specific capacitance of 190 F/g at a 5mV/s scan rate with a retention rate of 92% after 2000 cycles. The successful combination of a sustainable process and using the waste resources as a raw material in energy storage applications suggests a great perspective for the underutilized waste coffee grounds.