In this study, the cost of working electrode was reduced greatly by replacing glassy carbon electrode (GCE) with 2B pencil. The pencil lead was modified with carbon nanotubes (CNTs) for simultaneous and quantitative detection of hydroquinone (HQ) and catechol (CT). The surface morphology of CNT-modified pencil electrode (PE-CNT) was studied by scanning electron microscopy (SEM) whereas electron transfer properties were evaluated through electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). This electrode evinced an enhanced redox reversibility and superior electrocatalytic performance concerning HQ and CT. Consecutive concentration variation studies exhibited linearity in oxidation peak responses up to 300 μM for each of the analytes with a detection limit (S/N = 3) as low as 1.5 and 0.7 μM for HQ and CT, respectively. We proposed a possible mechanism for their sensitive detection. The developed sensor was successfully examined for real sample analysis with tap water and it exhibited a stable and reliable recovery data with high reproducibility. The cost of the 2B pencil is 1000 times lower than that of GCE. Thus, the 2B pencil can be a good alternative to GCE in electrochemical sensor fabrication due to its economic advantage.

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The efficiency of any electric cell or battery is very important. To keep it in mind, the coulombic efficiency, voltaic efficiency and energy efficiency have been studied. It was found that the coulombic efficiency data illustrated that this efficiency was higher comparing to other efficiencies may be the absence of salt bridge or separator between the electrodes. However, the highest efficiency was obtained for 40% PKL (Pathor Kuchi Leaf) sap with 5% secondary salt in 55% aqueous solution, which implies that the concentration of PKL juice can play an important role regarding efficiency. It was also found that the average energy efficiency was 97.43%, and it was also found that the average voltaic efficiency was 57.29%. Temperature effect of the PKL electrochemical cell has also been studied. It is found that the ideal temperature for this PKL electrochemical cell is room temperature and it is from 20 to 40 °C. But, it is also usable at a lower temperature from 5 to 60 °C as like as other standard cells. Most of the results have been tabulated and graphically discussed.

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