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Building an Arduino Based Potentiostat and Instrumentation for Cyclic Voltammetry

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Building an Arduino Based Potentiostat and Instrumentation for Cyclic Voltammetry JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 Building an Arduino based potentiostat and Instrumentation for Cyclic Voltammetry Joshi P.S1, Sutrave D.S2 1Walchand Institute of Technology, Solapur-413006, Solapur University, Maharashtra, India 2D.B.F Dayanand College of Arts and Science, Solapur-413002, Solapur University, Maharashtra, India. [email protected], [email protected] Abstract: Potentiostat is prime devices in modern electrochemical research particularly in the investigation of mechanism reaction related to redox chemistry reaction and other chemical phenomena. Cyclic voltammetry can be performed with most of the commercially available potentiostats. A potentiostat consisting of operational amplifiers is reported. An Arduino based instrumentation designed for cyclic voltammetry characterization was used to study the redox reaction occurring at the electrode-electrolyte interface. The specific capacitance was calculated which is in good agreement in comparison with standard electrochemical workstation. The simple design, construction, easy to operate, low cost and good performance are the advantages of the instrumentation. Keywords: Electrochemistry, Potentiostat, Cyclic voltammetry, Arduino Introduction Cyclic voltammetry (CV) has become a significant and broadly used electroanalytical technique in many areas of chemistry. It is generally used for the study of redox processes, in the analyses of electrochemical reactions between ions and surface atoms of electrodes under the investigation for understanding reaction intermediates for obtaining stability of reaction products, for qualitative information on electrode reaction mechanisms, qualitative properties of the charge transfer reactions between electrolyte ions and electrons from the electrode surface[1-3].Thus it is a powerful technique to study the redox reaction which plays a key role for charge storage mechanism in the study of supercapacitor. Cyclic voltammetry is based on varying the applied potential at a working electrode in both forward and reverse directions (at some scan rate) while observing the current. This technique involves a linear and a cyclic variation of electrode potential between the working and reference electrodes within a potential window by measuring the current that flows between working and counter electrodes. A certain potential is applied to a certain surface of electrode by potentiostat, which increases or reduces the amount of electrons on the surface. This forces the electrolyte to be triggered to consume electrodes to compensate for this. The exchange of electrons per time i.e. electrode’s current is measured by potentiostat. So, potentiostat is the electronic hardware which controls the three electrode cell and usually described in terms of simple operational amplifiers. Presently several companies manufacture high quality potentiostats capable of performing various voltammetric techniques. Cypress systems, ACM Instruments, EcoChiemie Netherlands, EG & G Princeton Applied Research are the top manufacturers. As per the requirement, the potentiostats may vary by size, power, sophistication and price. Though number of companies is manufacturing potentiostat instruments that deliver high precision but they are at equally high cost. These manufacturers usually make available the software for data analysis, electrochemical cells and the electrodes. Typically, these instruments along with software cost from $5,000 to $20,000. Due to such a high cost, these instruments are not easily reachable for academic reason or for preliminary research study. Also there are a number of low cost potentiostats which deliver low accuracy or resolution. The three basic components of a potentiostat are control amplifier which supplies power to maintain the controlled potential between working and reference electrode, an electrometer which measures the potential difference between the reference and working electrode and I-V converter hat measures the current between working and counter electrode. The major goal of the work is to create a microcontroller based scanning system which can accept the given input voltage range (in both positive and negative directions) and record the corresponding change in current. This voltage is provided by potentiostat. Hence the main concern is to design a potentiostat having simple circuit with a low cost and low component count . Volume V, Issue XII, December/2018 Page No:163 JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 Potentiostat Design: Potentiostat consists of operational amplifiers as shown in figure. The circuit has two parts. First part as shown in figure 1. Provides the necessary power supply or potential to working electrode. This is then fed back to the same through electrolyte and reference electrode. The amplifier in this stage protects the DAC output from loading. This keeps the DAC voltage non-distorted upto the working electrode end of potentiostat. The buffer stage at the working electrode end ensures that the potential at working and reference electrode remains equal. This is the main and utmost required condition in cyclic voltammetry analysis and potentiostat design. Fig 1.Schematic of Potentiostat –Part 1 Second part , Transimpedence amplifier is as shown in figure 2. This stage converts the small amount of current through electrolyte into the voltage. Fig.2 .Schematic of Potentiostat –Part 2 The proposed instrumentation for cyclic voltammetry system using this potentiostat consists of ADC[4], DAC [5] , an Arduino microcontroller board (Arduino mega, Arduino)[6] to control the parameters, keypad[7] , LCD[8], USB flash drive[9] and an electrochemical cell. Figure 3. shows the photograph of PCB developed. Volume V, Issue XII, December/2018 Page No:164 JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 Fig. 3. Photograph of PCB developed. The detail functioning of each component is published elsewhere[10].System will start and initialize to get parameters. The required parameters such as scan rate and voltage scan range are given as input through keypad. After settings, user will press the START button. The system will scan in the predefined loop/ range.LCD will indicate the completion of cycle/ scan. The data is stored in USB flash drive. Figure 4. shows our developed system with electrochemical cell and computer. Fig. 4. Set-up for Cyclic Voltammetry Specific Capacitance determination: Cyclic voltammetry was carried out using an electrochemical cell consisting of metal oxide thin film as working electrode, Pt auxiliary electrode as counter electrode and a saturated Calomel electrode as reference electrode. For this Mn doped Ruthenium Oxide (at % 2) thin film was used as working electrode. The cyclic voltammetry was carried out in a potential window -0.8 V to 0.6 V for three different scan rates 10 mV/Sec, 50 mV/Sec and 100 mV/Sec in a 0.1 M KOH electrolyte. Here the voltage is stepped in 0.1 V upto final voltages. Volume V, Issue XII, December/2018 Page No:165 JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 After completion of the predefined scan, the data is stored in USB flash drive and used for further analysis. The data stored in USB was used for further analysis. Figure 5. shows the cyclic voltammogram plotted from the data. The rectangular shape of CV curve showed the supercapacitive behaviour. Also the area under the curve was increased with increase in scan rate which in turn decreased the specific capacitance. Our system showed the similar results as the laboratory tests. Fig. 5. Cyclic voltammogram for Mn: RuO2 thin film electrode from developed CV system Table 1. shows the specific capacitance comparison between CHI 608E electrochemical workstation and our developed system for different scan rates. These values are comparatively less than the laboratory test values. Table 1. Specific Capacitance CHI 608E Developed Scan rate Electrochemical System (mV/sec) workstation (F/g) (F/g) 10 307 262 50 229 149 100 202 124 The difference in value may be because of low resolution and sophistication. CONCLUSION It is demonstrated that the fabrication and design of a simple potentiostat is capable of performing cyclic voltammetry according to user-inputted parameters. It is possible to accept the voltage in both directions, to generate the step voltage increase of 0.1 V, to measure the corresponding current and to store the data in USB flash drive which can be used for analysis and to display the input variables, start and end of the process. The system is set for three different scan rates i.e 10 mV/Sec, 50 mV/Sec and 100 mV/Sec. The results obtained show the rectangular shape of voltammogram giving supercapacitive behaviour. Successful scanning in both positive and negative voltage windows, generation of satisfactory and bipolar current, increase in current density, increase in area under the curve and decrease in specific capacitance with increase in scan rate are seen from results .The similar observations are seen as compared to laboratory tests. Volume V, Issue XII, December/2018 Page No:166 JASC: Journal of Applied Science and Computations ISSN NO: 1076-5131 References [1] Princeton Applied Research, Applied Instrument Group, Basics of voltammetry and polarography, Application Note P-2, pp 1-12. [2] J. Wang, Analytical Electrochemistry, Chapter 2, John Wiley & Sons (2000). [3] R.S. Nicholson and I. Shain, Theory of stationary electrode polarography, single scan and cyclic methods applied to reversible,
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