Microporous activated carbons from used coffee grounds for application to electric double-layer capacitors

Abstract

Electrochemical double-layer capacitors (EDLCs) are devices that store enormous amounts of charge electrostatically when a potential is applied between electrodes of very high surface area (typically made of porous carbon) and an electrolyte. Wider commercialization of this technology has been held back by the lack of ultralow-cost electrode materials. We demonstrate that used coffee grounds can be processed to form low-cost electrodes. The surface and electrochemical characteristics of microporous activated carbons from used coffee grounds (CGCs) were measured. First, optimal times and temperatures for carbonization and activation were identified on the basis of Brunauer-Emmett-Teller (BET) surface area, pore volume, and pore size distribution. Second, CGCs were used as polarized electrodes in EDLCs, whose capacitances were evaluated using cyclic voltammetry. The results show that carbonization for 1 h at 600 • C with a heating rate of 300 • C/h, followed by CO 2 activation for 2 h at 1000 • C, affords the highest BET surface area (1867 m 2 /g) compared to other works. The produced CGCs have many micropores of less than 2 nm across, which contribute to the formation of an electric double layer. Capacitors made using these CGCs show the highest capacitance (103 F/g) in 0.8 M (C 2 H 5 ) 4 NBF 4 /PC as an organic electrolyte, which is much higher than the ∼80 F/g typically used in organic-electrolyte-based commercial EDLCs, suggesting that coffee grounds are a useful electrode material.

Spin‐thermoelectric voltage in longitudinal SSE elements incorporating LPE YIG films and polycrystalline YIG slabs with an ultrathin Pt layer

“…On the other hand, as regards the experimental value of I = V STE / R Pt defined in Equation as an equivalent current due to ISHE, it was slightly larger at t Pt = 3‐2.5 nm than at 4 nm, but halved at t Pt = 1 nm with the highest V STE . Nowadays, extensive research is conducted on electric double‐layer capacitors as elements supporting a broad voltage range, and the STE conversion elements combined with these capacitors may be used to create electric storage systems. In this case, there is a need to examine the STE element length required to obtain the necessary voltage, as well as ISHE currents required for charge accumulation.…”

The second life of coffee can be even more energizing: Circularity of materials for bio-based electrochemical energy storage devices

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Study of activated carbon characteristic from ketaping fruit shell (Terminalia Catappa) as supercapasitors electrode

“…Sebagian besar karbon aktif komersil yang dibuat dari bahan bakar fosil minyak bumi dan batu bara menjadikannya sangat mahal dan tidak ramah lingkungan, sehingga penelitian beralih pada sumber karbon aktif dari biomass limbah organik yang lebih murah, mudah didapat dan ramah lingkungan (Abioye and Ani, 2015). Berbagai penelitian telah banyak dilakukan dalam penggunaan sumber karbon aktif dari biomass limbah organik sebagai elektroda superkapasitor seperti limbah bubuk kopi (Tashima et al, 2014), daun ketaping (Taer et al, 2018), cangkang kelapa sawit (Misnon et al, 2015), enceng gondok (Zheng et al, 2017), tandan kosong kelapa sawit (Farma et al, 2013), dan cangkang biji karet (Pagketanang et al, 2015). Pada penelitian ini dipilih CBK yang banyak ditemukan di daerah Sumatra barat khususnya daerah ketaping sebagai sumber karbon aktif karena mudah didapat, melimpah, terbarukan dan berkontribusi terhadap pengurangan limbah organik.…”