Nanocomposites and nanomaterials

Adsorption properties of nanoporous carbon materials obtained from waste coffee grounds
Sklepova S-V.S., Gasyuk I.M., Ivanichok N.Ya., Soltys A.M., Klymkovych S.M., Lisovskiy R.P., Rachiy B.I.
The Department of Material Science and New Technology, Vasyl Stefanyk Precarpathian National University. 57 Shevchenko Str., Ivano-Frankivsk, Ukraine.
E-mail: sonja93sklepova@gmail.com

Nanoporous carbon materials (NCM) are used to prepare supercapacitor (SC) electrodes. The high specific energy characteristics of SC are closely related to the physicochemical characteristics of NCM. NCM with a highly developed surface area and controlled pore size distribution can be obtained by chemical and thermal activation of carbon containing precursors. In our work we propose a method of obtaining NCM with a high specific surface area. The NCM is obtained by thermochemical activation of potassium hydroxide waste coffee grounds (WCG). The WCG, from commercial beverage manufacturers, was dried at 65-85 °C for 48 h. The dried WCG was mixed at a weight ratio of 1:0.5:1 with KOH and distilled water. The resulting mixture was stirred thoroughly for 1-2 hours; after which it was dried at a temperature of 90 ºC. The dry material was placed in an autoclave and heated to a given temperature and kept at this temperature for 30 min. After cooling, the resulting material was washed to neutral pH and dried at 90 ºC. The series of samples (S400 ÷ S900) were numbered according to the thermochemical activation temperature. For example, S900 is a material activated at 900 ºC. The table shows the characteristics of the porous structure of NCM.
The parameters of the porous structure of the NCM
Sample	S400	S500	S550	S600	S700	S800	S900	
SBET, m2/g	31	172	246	374	446	703	1056	
SDFT, m2/g	23	193	218	309	478	632	1170	
Smeso, m2/g	30	44	30	27	27	22	45	
Smicro, m2/g	-	80	175	319	402	671	996	
Vtotal, cm3/g	0.092	0.161	0.176	0.228	0.237	0.331	0.507	
Vmicro, cm3/g	-	0.038	0.071	0.132	0.162	0.272	0.398	
The specifications of porous structure (it means surface area and general volume) of NCM were determined on the basis of analysis of adsorption/desorption isotherms of nitrogen. A number of complementary methods BET, DFT, BJH and t-method were used.