Preparation of Bioorganic Rechargeable Battery Using Urea and Chickpea Protein for the Storage and Generation of Electrical Power.
Summary: The concept of the organic rechargeable battery is introduced. This battery is using urea as oxidation half and the aqueous extract of chickpea as reduction half due to the reversible electrochemical oxidation and reductions of the of the urea and chickpea proteins. Organic rechargeable battery is composed of five cells. Each of the half cell of which is made of a cubical container of high density polyethylene joined to the other through epoxy resin. Non porous graphite rods of 40 mm diameter and 400 mm length were used as the inert electrodes of the battery. The electrodes were placed in aqueous solutions of urea and chick pea extract in separate containers. Sodium hydroxide was used as the electrolyte of the process. The experimental conditions for this five cell battery were optimized. The net voltage and the stability of the voltage were investigated.
The variation in stability and voltage was investigated as a function of the salt bridge, concentration of electrolyte, amount of oxidizing and reducing agent and the viscosity of the media. The battery prepared was giving a voltage of 9.5 volt.Keywords: Organic rechargeable battery, Urea oxidation, Chickpea reduction, Low power battery, Protein reduction
Oxidation and reduction reactions are important due to their biological significance, energy generation and energy storage [1-3]. The oxidation process is also important for the generation of electricity in fuel cells [4,5]. The role of oxidation and reduction in cosmetics and cosmaceuticals is also important and hair removing and hair curling are also the result of these reactions [6,7]. Both, these phenomena are due to the oxidation and reduction of sulfur-containing proteins and amino acids. The amino acids cysteine and cystine are the oxidized and reduced form of each other. In addition to hair, sulfur-containing amino acids are also found in pulses. The metabolic activities are associated with the generation of urea from the amino acids which is produced by the oxidation of amino acid . Urea may pass through oxidation under appropriate conditions  and the anodic oxidation of urea is also reported .
We believed that in aqueous solution the oxidized form of urea remains in equilibrium with the urea. It may form a cell if coupled with a half cell observing reduction reaction. In case of the tendency of the half cell for electrolytic reverse reaction, the resulting cell will be a rechargeable cell. Recently our research group introduced a rechargeable battery and voltaic cell using protein for the storage of electricity . Voltaic cells are important in terms of the transformation of chemical energy into the electrical energy. Electricity generation in living systems is important in the defense of the organisms or other important functions. All these involve the biochemically active compounds including proteins.
The present work is aimed to investigate the possibility of organic pollutants or other organic waste to be utilized for the storage and generation of electricity. This will lead to reduction of the mass of battery as compared to the lead storage battery as well as eco-friendly. One of the other aims is to investigate an easy procedure for the detoxification of the compounds like urea for those having impaired natural detoxification system. This work is also aimed to resource generation from these types of waste and to utilize the chemical energy of waste. The possible outcome of this work also includes the development of a novel method for the analysis of proteins and other organic compounds which can pass through electro-oxidation or reduction. It may also result an electrochemical method for the determination of the antioxidant activities.
Results and Discussion
Theory of the rechargeable urea protein
Antioxidant activities of the chickpea and other pulses [12, 13] allow the use of the extracts of these as oxidation or reduction half of a battery. These activities are believed to be due to the sulfur- containing proteins / peptides or amino acids. Based on the cysteine and cystine equilibrium [14, 15], these proteins can be used as oxidation or reduction half cell of a battery e.g. in case of a strong oxidizing agent it acts as reducing half. Urea converts into ammonium carbonate on oxidation and this oxidation reaction may be carried out electrolytically.
In the present work the urea half cell containing an aqueous basic solution of urea was coupled with a half cell containing a water extract of chickpea and basified with 0.5 M NaOH solution. Urea half formed the anodic side, and the chickpea cathodic half. The cell was found to give a voltage of 820 millivolt without charging, however, on charging the voltage was 1900 millivolts. Using cysteine and cystine as model the proposed reaction for the protein half is given as following.
Analysis of the product
The anodic half of the cell was loaded with an aqueous solution of urea. The urea half was analyzed for the carbonate contents, its solution was found to react with lime water or calcium chloride yielding a white precipitate. It was observed that formation of carbonate decreased its voltage generation capacity.
Effect of salt bridge on the voltage and stability of urea protein battery
The salt bridge connects the two solutions of the half cells. It was observed that the nature of the salt bridge is also important for determining the voltage and stability of the battery. The use of a highly porous salt bridge gives less stable voltage. It is due of the tendency of the mixing of solutions through capillary action which results the establishment of the equilibrium in terms the free energy of both the solutions. These investigations were carried out using a single cell. The recharging time was 15 minutes and the charger for these experiments was of 12 volt strength. The results of these investigations are summarized in Table-1. If a salt bridge of a spirit lamp wick, composed of loose threads, was used, the voltage and stability is less compared to the usage of a compact wick composed of waved wires as used in lanterns.
The lamp wick is acting as salt bridge due to its ability to take and retain the basic solution which act as the electrolyte and salt bridge for connecting the two solutions. In case of the use of a card board as a salt bridge, a further increase in stability and voltage was observed. This is because of the ability of the card board to avoid the mixing of the solutions.
Table-1: Investigation of the suitable salt bridge for urea protein battery.
S. No.###Salt bridge nature###Max voltage (Millivolt)
1###Spirit lamp wick###800
2###Waved thread wick###1500
Investigation of the power of charger on the charge storage capacity of cell:
It has been mentioned in the theoretical basis of the battery that urea half may pass through reversible electrochemical oxidation and the chick pea pass through reduction. The active components of the cell are produced as a result of the complex equilibria of the cell and the active concentration of the components is formed due to the electrochemical reaction. Some of these reactions are voltage dependent and electrochemical reactions finally lead to the formation of active species. Therefore, change in the power of charger / transformer changes the voltage of the resulting species and charging time. An increase in the voltage of power supply decreases the charging time and increases the voltage of the resulting cell. This is due to change in the value of equilibrium constant due to larger value of the input energy. All studies were carried out using a single cell and each experiment was carried out in triplicate.
The charging time was 10 minutes for each of the experiments and results are given in Table-2. It can be seen from the results that the voltage increases with increase in voltage of the charger. The effect of the power of the charger on the voltage of the cell was not explored beyond this due to the non- availability of the chargers in our laboratory. However, it is expected that this increase will occur until a limiting value. This limiting value is based on the availability of the active species which are coming to the solution through electrochemical reaction. Although the voltage is greater in case of the 30 volt charger but we used 12 volt charger for further research.
Table-2: Investigation of the power of charger on the charge storage and capacity of cell.
S. No.###Voltage of the###Voltage of cell/ battery
Investigation of the optimum time of charging for the urea-protein cell
This bioorganic battery works on the oxidation and reduction capacity of urea and proteins, respectively. Both, the voltage and stability of resulting cell is a function of the concentration of these species. The concentration of these depends upon the kinetics of the electrically generated species. It is important to have maximum concentration of these species. The concentration of the active species depends upon the charging time and the power of the charger. This study was carried out using five cells in a battery and it was recharged using a 12 volt transformer. Each of the experiment was carried out in triplicate and the results of this study are given in
Table-3. It indicates that the voltage changes with change in charging time. It can also be observed that after 15 minutes the maximum concentration of the active species become constant and the voltage get a limiting value. Based on the voltage of the cell, 15 minutes charging time was selected for further work.
Table-3: Investigation of the optimum time of charging for the urea-protein cell.
S. No.###Time of charging###Voltage (Millivolt)
Investigation of the optimum amount of chickpea and urea for the preparation of urea protein bioorganic battery
It is believed that urea solution and chickpea extract contains hydrolyzed species (peptides amino acids and hydrolyzed form of urea) which pass through oxidation and reduction reactions. The oxidized and reduced forms are in a state of equilibrium. The energy transfer and storage reactions depend upon the concentration of active species in the cell. Therefore, change in concentration of the starting material also changes the active concentration which changes the capabilities of the cell according to Nernst's equation. These studies were carried out using a single cell containing urea half and chickpea half separated by a salt bridge made of hard board.
The strength of the charger was 12 volt and the charging time was 15 minutes. Each of the experiment was carried out in triplicate and the results are given in Tables-4 and 5. It can be seen from Table-4, that a cell of maximum voltage is obtained when the extract was obtained from 10 g of boiled chickpea per 100 mL of the solution. This concentration contains maximum amount of the active species and was selected as optimum for onward studies. The results for urea optimization are given in Table-5. The results indicate that 2% of urea is the optimum concentration for the urea protein bioorganic battery. It can be seen from Table-5 that the voltage decreases of the cell decreases with increase in concentration beyond certain limit, this may be due to a number of reasons, one of that might be the complex electorchemical reaction of the NH2 of the urea with increase in concentration  which may stop the voltage generating reaction.
Table-4: Investigation of the optimum amount of chickpea for the Preparation of urea protein battery.
S. No. Mass of pulse (Gram)###Mass of urea (Gram)###Voltage with###Voltage after
###Out Charging (Millivolt)###charging (Millivolt)
Table-5: Investigation of the optimum amount of urea for the Preparation of urea protein battery.
S. No. Mass of pulse (Gram)###Mass of urea (Gram)###Voltage with###Voltage after
###Out Charging (Millivolt)###charging (Millivolt)
The effect of the concentration of NaOH on the voltage of rechargeable urea protein battery cell Both, urea and the extract of chickpea have high resistance and both of these have the tendency of redox reactions. The resistance of the cell can be controlled by the use of electrolytes. In this work NaOH solution in different concentrations was used as electrolyte. The use of NaCl or acid was avoided due to the formation of toxic gaseous products by the electrolysis of these compounds in charging of the cell. The addition of NaOH solution also facilitates hydrolysis and oxidation reduction process that is why optimum concentration of NaOH was investigated for this cell. The voltage of the cell changes with change in concentration of the NaOH solution as shown in Table-6. Based, on the voltage after charging of the cell 5% NaOH was selected as the optimum concentration of NaOH.
Table-6: Investigation of the optimum concentration of sodium hydroxide solution for the preparation of urea protein battery.
S.###NaOH (M)###Voltage without###Voltage after
Investigation of the power of urea protein battery
The stability and power of the urea protein bioorganic battery was investigated using a five cells battery. This battery stores and generates voltage due to the oxidation of urea and reduction of the protein in the water extract of the chickpea. The stability and power of this cell was investigated by the use of LEDs as power consumers. The specifications for which are given as: 1 V = 800-1000, V F (V) = 3.2- 3.8, power dissipation = 80 mW. It was observed that the five cell battery give a maximum voltage of 9500 millivolts and a current of 100 mA on complete charging. This voltage was determined in open circuit measurement.
It was further observed that the voltage drop down from 9.5 to 5.5 volt when a set of five LEDs were used as load. This battery has less power than the chickpea and kidney beans battery recently introduced by our group . However gum arabic was added to the half cells the stability and voltage increased. It can be observed from the Table-7 that a set 5 LEDs work for 10 minutes and 15 seconds. Based on this the power of battery was found 1.0 Watt. Whilst in case of the gum added battery this time was found 25 minute and 10 second. This may be due to the stability of charge by change in viscosity which results increase in power.
This indicates that the power and stability of this battery can also be controlled by the additives. The electrical energy is stored as chemical energy in the cell. The free energy of the cell can be conserved by changing the viscosity of the medium of the cell. The increase in viscosity of the media lowers the movements of the species involved in storage of the electrical energy. It also retains the charge difference which leads to the conservation and stability of the voltage of the cell. To check, whether this is the effect of the composition of the gum arabica or the viscosity which changes the power, a gum used by the book binders was added to the cells instead of the gum arabica. In this case the results were found similar to the gum arabica added battery. This indicates the effect of the viscosity of the media on the power and stability of this battery.
Table-7: Investigation of the power of urea protein battery.
S. No.###No of LEDs###Time
1###1###14 min 2sec
2###2###12 min 35 sec
3###3###11 min 25 sec
4###4###10 min 15 sec
5###5###8 min 42 sec
Material and Method
The urea protein battery is composed of 5 units and each unit is prepared by joining two cubical epoxy resin containers each of which has a volume of 3.2 cm3, a cut was made in the joining walls for facilitating the salt bridge. Salt bridges of different material were used including a wick of a sprit lamp, a wick composed of waved threads (used as wick in lanterns) and piece of card board. The electrodes made of made of non porous graphite were placed in a strip of card-board. Each of the electrodes is a rod shaped inert electrode of 40 mm diameter and 400 mm length.
These were connected through a copper wire according to the circuit requirements. Each of the cells was loaded with an aqueous solution of bioorganic material followed by placement of electrodes. This solution also contain sodium hydroxide as electrolyte and processes facilitating material. The voltage and out put current was measured by the use of a Fluke 112 digital multimeter. Charging was carried out using indigenously-prepared chargers of various strengths according to the procedure.
From presented research, forced oxidation- reduction reactions and volunteer reactions were found possible by the coupling two half reactions. It was observed that joining of the oxidizing half cell with reducing half cell gave a net voltage. The magnitude of cell voltage can be increased by charging process which indicates the forced oxidation and reduction reactions. The voltage and stability of the battery was found to be changed with changes in the nature of salt bridge and the nature of the reactants. Bioorganic battery can be improved by working on these parameters and can be used for a number of purposes in addition to the power storage. This bioorganic battery can be used for the dissolution of tumors through smaller voltages for avoiding complications. It provides a safe and economical and useful disposal of the proteinaceous organic waste.
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Department of Chemistry, Abdul Wali Khan University, Mardan, Pakistan. H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan. PCSIR Laboratories Complex, Karachi, Shahrah-e-Dr. Salimuzzaman Siddiqui, Karachi-75280, Pakistan. email@example.com, firstname.lastname@example.org
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|Author:||Hussain, Zahid; Khan, Khalid Mohammed; Ullah, Aman; Shah, Akram; Saeed, Faiq; Perveen, Shahnaz|
|Publication:||Journal of the Chemical Society of Pakistan|
|Date:||Oct 31, 2013|
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