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Nanotechnology allows the synthesis of nanoscale catalysts, which offer an efficient alternative for fuel cell applications. In this laboratory experiment, the student selects a cost-effective anode for fuel cells by comparing three different working electrodes. These are commercially available palladium (Pd) and glassy carbon (GC) electrodes, and a carbon paste (CP) electrode that is prepared by the students in the laboratory. The GC and CP were modified with palladium nanoparticles (PdNP) suspensions. The electrodes efficiencies were studied for ethanol oxidation in alkaline solution using cyclic voltammetry techniques. The ethanol oxidation currents obtained were used to determine the current density using the geometric and surface area of each electrode. Finally, students were able to choose the best electrode and relate catalytic activity to surface area for ethanol oxidation in alkaline solution by completing a critical analysis of the cyclic voltammetry results. With this activity, fundamental electrochemical concepts were reinforced.

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The electrochemical properties of L-cysteine self assembled monolayer on palladium surface has been investigated. The effect of immobilization time of L-cysteine monolayer on palladium was studied by cyclic voltammetry (CV). Further, the electron transfer of the Fe(CN)63-/4- redox couple at different pH values was used to evaluate the protonation and deprotonation of the functional groups (NH2, COOH) at the modified electrode surface by using CV and electrochemical impedance spectroscopy (EIS). When the pH of the solution is high (ca. 11), the monolayer posses negative charge, Fe(CN)63-/4- current is inhibited. On the contrary, a different behavior at low pH (ca. 2) has been found. From the data obtained by CV and EIS, the surface pKa was found to be 7.3 and 7.1, respectively. At pH 7, we have compared Fe(CN)63-/4- peak currents as a function of scan rate, at different supporting electrolytes.

The electrochemical oxidation of NADH has been evaluated using palladium surface modified with self assembled monolayer of L-cysteine. The alcohol dehydrogenase (ADH) enzyme was immobilized onto L-cysteine monolayer using different routes; adsorption physical or entrapment of the enzyme using Nafion as polymer. These modifications were analyzed with Fourier transform infrared (FT-IR) spectroscopy and electrochemical techniques. The FT-IR was used to characterize the immobilization process of ADH in L-cysteine monolayer. In cyclic voltammetry we use a redox probe as Fe(CN)63-/4- in KNO3 for study the kinetic of the system. Also, we studied the electrochemical oxidation of NADH in bare palladium and Pd modified with L-cysteine monolayer. The results show that L-cysteine monolayer assembly on the electrode surface facilitates the NADH oxidation, allowing the oxidation at a less positive potential. Finally, we studied the electrocatalytic activity toward the oxidation of ethanol in presence of ADH immobilized at L-cysteine monolayer and NAD+ in solution for the detection NADH on the palladium surface.