SYNTHESIS OF GRAPHENE OXIDE USING MODIFIED HUMMER’S METHOD AND ITS APPLICATION AS COUNTER ELECTRODE IN DYE-SENSITIZED SOLAR CELL (DSSC)

• Main Author: OKVASARI (NIM :20514023), RUDINA
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/24121
• Institution: Institut Teknologi Bandung

Reduced graphene oxide is a graphene-like material that can be synthesized using so many methods. Chemical exfoliation by Hummer is one of the best methods to produce graphene oxide from graphite. This method becomes popular because the easy and low cost process, which can be divide into three major steps: (a) oxidation by sodium nitrate (NaNO3), (b) oxidation by potassium permanganate (KMnO4), and (c) oxidation by hydrogen peroxide (H2O2) 30%. Modification of Hummer’s method was done to obtain better graphene oxide. The first modification was burning the precursor in a high temperature to increase amorf phase in graphite. Combustion carried out for five minutes so it will leave graphite with more amorf structure and <br /> <br /> more oxidized in the edge. Graphite then reacted with sodium nitrate (NaNO3) in a concentrated sulphuric acid (H2SO4 97%). The second modification was replacement of Pottasium permanganate (KMnO4) with Ammonium persulphate (APS). This modification delivered a better oxidation of graphene layers in graphite. The next step was adding H2O followed by adding hydrogen peroxide (H2O2) 30% and H2O. The result of this chemical exfoliation was called graphite oxide. This graphite oxide was dispersed in H2O to loosen the bond between the layers. This stable dispersion then called graphene oxide. The reduction started with adding Sodium borohydrate (NaBH4) and Sodium hydroxide (NaOH) 1M into graphene oxide dispersion. The <br /> <br /> mixture than sonicated for two hours to loosen the interlayer bond of graphene in reduced graphene oxide. Sentrifugation was presented so the presipitant and the <br /> <br /> supernatant could be separated. The black presipitant then dried at 60 oC for 24 hours and so-called reduced graphene oxide. This reduced graphene oxide then used as counter electrode in Dye-Sensitized Solar Cell (DSSC). DSSC is a photovoltaic device that can converse the sun light radiation into electrical energy. Raman spectrocopy showed the ratio between D-band and G-band intensity (ID/IG) for (a) graphite at 0,1831, (b) graphite oxide at 0,8274, (c) graphene oxide at 0,9544, and (d) reduced graphene oxide at 1,1094. The ratio of ID/IG increased for reduced graphene iv oxide indicated the restoration of graphene bassal plane. Dispersion stability of reduced graphene oxide presented in several solvents and showed the different dispersion behaviour of graphene oxide and reduced graphene oxide. UV-Vis spectroscopy shows that reduced graphene oxide has the &#960;-&#960;* bond’s peak at 207 nm. It indicated that the sp2 bond could be replaced by reduction method. The fact that this peak shifted into the larger wave number showed that the reduction can not restore all the sp2 bonds. The conductivity of reduced graphene oxide showed a semiconductor graph with value 1,38 x 10-3 S cm-2. ThE semiconductor properties due to the left-over carboxylic group on the graphene bassal plane. Thin film fabrication used airbrush technique of rGO dispersion in NMP. Application of reduced graphene oxide as counter electrode in Dye-Sensitized Solar Cell coupled with polyaniline in emeraldine salt form (PANI-ES) in order to improve performance. A compositionratio of 1:3 between PANI-ES and reduced graphene oxide provides DSSC parameter value Jsc 7,5247 mA cm-2, Voc 0,6375 Volt, FF 0,4550, and efficiency of 2,5088%.