| Abstract | U ovom radu cilj je bio ispitati svojstva grafena i mogućnost upotrebe grafena kao aktivnog materijala u superkondenzatoru. U prvom koraku ovog rada provedena je redukcija grafen oksida (GO) u grafen (rGO) s NaBH4 kod pH=8 i pri 80°C. Dobiveni rGO je nanesen na elektrodu od staklastog ugljika (Elektroda11 i Elektroda12) te su ispitana kapacitivna svojstva ovako priređenih elektroda metodom cikličke voltametrije u otopini 0,5 mol dm-3 Na2SO4. Dobiven kapacitet za Elektrodu11 iznosi 17,56 F g-1 , a za Elektrodu12 13,9 F g-1. Osim uzorka priređenog u laboratoriju, ispitan je i komercijalno dostupan uzorak rGO (Elektroda22) koji pokazuje veću vrijednost specifičnih kapaciteta, odnosno 64,48 F g-1. Niži kapaciteti zabilježeni kod priređenog rGO posljedica su manjeg stupnja redukcije.
Od priređenog i komercijalno dostupnog uzorka rGO na podlozi od staklastog ugljika sastavljeni su superkondenzatori koji su označeni kao Superkondenzator1 (priređeni rGO) i Superkondenzator2 (komercijalni rGO). Između elektroda smješten je celulozni separator natopljen otopinom 0,5 mol dm-3 Na2SO4. Ispitivanje svojstava superkondenzatora provedeno je metodom cikličke voltametrije i kronopotenciometrije. Za Superkondenzator1 specifični kapacitet dobiven metodom cikličke voltametrije iznosio je 3,49 F g-1, dok za Superkondenzator2 iznosi 6,45 F g-1. Metodom kronopotenciometrije, osim vrijednosti specifičnog kapaciteta, određene su vrijednosti specifične snage i energije. Za Superkondenzator1 dobiveni specifični kapacitet iznosi 3,32 F g-1, energija 2,39 W s g-1 i snaga 0,12 W g-1, dok za Superkondenzator2 specifični kapacitet iznosi 18,81 F g-1, energija 13,54 W s g-1 i snaga 0,12 W g-1. S obzirom da je kod Superkondenzatora2 dobiven veći specifični kapacitet i energija, proizlazi da Superkondenzator2 pokazuje bolja svojstva u odnosu na Superkondenzator1. Međutim kod Superkondenzatora2 je dobivena puno lošija stabilnost s povećanjem broja ciklusa punjenja i pražnjenja što je najvjerojatnije posljedica loše izvedbe superkondenzatora. |
| Abstract (english) | The objective of this research was to study the properties of a graphene and the possibilities of its usage it as an active material in a supercapatitor. The first step of this research was the reduction of graphene oxide (GO) to graphene (rGO)s which was carried out using NaBH4 and at pH=8 at 80°C. The obtained rGO was dropcasted on a glassy carbon support (Electrode11 and Electrode12) and then the capacitive properties of the electrodes were studied by applying cyclic voltammetry method in 0,5 mol dm-3 Na2SO4 solution. The values of specific capacitance for the Electrode11 and Electrode12 are 17.56 F g-1 and 13.9 F g-1, respectively. Apart from the samples synthesized prepared in the laboratory, a sample of commercially available graphene was also tested. The purchased sample shows higher value of the specific capacitance, equal to 64.48 F g-1. Lower capacitance values obtained for the prepared rGO are the result of a lower reduction degree of graphene sample. The Supercapacitor1 (prepared rGO) and the Supercapacitor2 (purchased rGO) are assembled using rGO samples on the glassy carbon support. A cellulose separator soaked in a solution 0,5 mol dm-3 Na2SO4 is placed between the electrodes. The testing of the supercapacitors was conducted by the cyclic voltammetry and chronopotentiometry methods. The specific capacitance of the Supercapacitor1 obtained by cyclic voltammetry method was 3.49 F g-1, while the specific capacitance of the Supercapacitor2 was 6.45 F g-1. Besides the specific capacitance value, the values of the specific power and energy were also determined by chronopotentiometry method. For the Supercapacitor1 the values of the obtained specific capacitance, energy and power are 3.323 F g-1, 2.393 W s g-1 and 0.12 W g-1, respectively. Whereas the obtained specific capacitance, energy and power for the Supercapacitor2 are 18.81 F g-1, 13.54 W s g-1 and 0.12 W g-1, respectively.
Since the Supercapacitor2 has greater specific capacitance and energy, it follows that the Supercapacitor2 shows better properties than the Supercapacitor1. However, much worse stability with the increasing number of charge/discharge cycles was obtained for Supercapacitor2 which is probably due to the poor performance of the supercapacitor. |
