ELECTROOXIDATION OF COCONUT OIL IN ALKALINE ELECTROLYTE

Providing more and more energy is an essential task of the today’s energetic industry. In the last few years, in addition to the traditional methods of energy production, alternative energy sources have been developing fast. One of the devices that can make use of these sources is a fuel cell. The fuel cells can be a power source of future mainly due to their high efficiency, low influence on environment and the possibility of powering with different fuels. Most often, fuel cells are powered by hydrogen. However, the problems with its cheap production and storage are the reason for the search for alternative fuels for fuel cells. It is important that the new fuel will be characterized by zero or low emission level. One of these fuels can be vegetable oil. The paper presents the measurements pertaining to electrooxidation of coconut oil emulsion on a smooth platinum electrode in an aqueous solution of KOH. The electrochemical measurements were performed in a glass cell with AMEL System 5000 potentiostat. The obtained maximum current density is equal to 25 mA/cm2. Therefore the coconut oil can be used as fuel for fuel cell provided that the temperature of process is kept above 303K.


INTRODUCTION
The energy consumption has increased greatly in recent years, mainly due to an improving standard of living.Currently, the energy production is generally based on coal, crude oil, natural gas or nuclear energy.Additionally, some alternative energy sources have been developed.One of the devices that can use these sources is a fuel cell (FC).The theoretical efficiency of a fuel cell can be equal to 100%.In fact, the real efficiency varies between 40-80% [Stolten 2010, Hoogers 2004, O'Hayre at al. 2005].Moreover, the fuel cells are characterized by zero or low negative influence on the environment and silent operation.Most often, fuel cells are powered by hydrogen [Hoogers 2004, Larminie and Dicks 2003, Rifkin 2003; Steele and Heinzel 2001, Stolten 2010].However, problems with cheap production and storage of this fuel are the reason for the search of new fuels for FCs, also using biofuels [Hamnett 1997 .However, it is necessary to examine the possibility of using coconut as fuel for fuel cell.In this case, electrooxidation of coconut oil should be carried out to determine the basic possibility of electrooxidation of this substance.
Theoretically, current density can be described by the Butler-Volmer exponential function [Bockris and Reddy 2000]. where where: η act -activation overpotential [V] K -the factor of dependence of activation overpotential on reaction speed Unfortunately, despite extensive knowledge in the field of solid-state physics and kinetics of catalytic reactions, the implementation of the catalysts is carried out mainly experimentally.The coconut oil and emulsion were heated during mixing.Coconut oil is a solid substance at room temperature.Therefore, the constant temperature of at least 298K was maintained during measurements.Figure 1 shows view of coconut oil at temperature 293K and 303K.

MATERIAL AND METHODS
The measurements were done with the method of polarizing curves of coconut oil emulsion electrooxidation in glass vessel on a smooth platinum electrode in KOH electrolyte.Before the measurements were perfored, the electrode (Pt) was degreased in 25% aqueous solution of KOH, digested in acetic acid and washed with alcohol.Platinum was used as a catalyst of the working electrode, due to excellent catalytic properties, while saturated calomel electrode (SCE) was used as a reference electrode [Twigg 1989, Bockris and Reddy 2000, Holtzer and Staronka 2000].The electrochemical measurements were performed in a glass cell with AMEL System 5000 potentiostat connected with a computer.
Figure 2 shows the scheme of research position for measurements of coconut oil emulsion electrooxidation.
The studies on electrooxidation of the emulsion based on coconut oil in an alkaline electrolyte (aqueous solution of KOH), for various concentrations of oil and detergent, and at various temperatures (303-348K) are presented in this paper.

RESULTS
The electrooxidation measurements of sole Syntanol DS-10 in alkaline electrolyte (aqueous solution of KOH) were carried first.This measurement enabled to assess whether the current density was formed from the electrooxidation of coconut oil emulsion or only from the detergent.Figure 3-5 shows the polarization curves of coconut oil emulsion electrooxidation in various concentration of oil.The electrooxidation was carried out at the temperature of 303-348K.

CONCLUSION
The greatest difficulty throughout the study was keeping coconut oil emulsion at constant temperature above 303K, Because the oil solidified, and precipitated from the emulsion below this temperature.The potential of the working electrode was establishing in time of about 25 minutes and was badly reproducible.Stationary, current-free real potential depends on waste engine oil concentration and is included in potentials range from 0.59-1.11V.
The current density of about 6-20 mA/cm 2 was obtained for all concentrations of coconut oil.With the increase in temperature above 333K, the first electrooxidation of Syntanol DS-10 took place.Therefore, the current density obtained from electrooxidation of Syntanol DS-10 above temperature 340K (fig.6) was higher than cur- rent density obtained from electrooxidation of coconut oil emulsion.The highest results of the potential were obtained at the temperature of 333K (25 mA/cm 2 ) (fig. 5).Thus, the fundamental possibility of electrooxidation of coconut oil emulsion on platinum smooth electrode in acid electrolyte (aqueous solution of KOH) was presented in this paper.The obtained current density and power of glass fuel cell is low, but it demonstrated a fundamental possibility of powering fuel cell with coconut oil.