Prof. Feliciano Research

l-cysteine modification of palladium (Pd) electrodes have been characterized using various electrochemical and surface analytical techniques such as cyclic voltammetry (CV), reductive/oxidative desorption, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and specular reflectance Fourier transform infrared (FT-IR) spectroscopy. The electron transfer reaction of l-cysteine modified Pd electrode was probed by employing  redox couple using cyclic voltammetry and electrochemical impedance. The CVs results revealed a quasi-reversible voltammograms for the Pd modified electrode, demonstrating that the electron transfer is not blocked due to surface modification. EIS results for the Pd modified electrode showed a decrease in the resistance in comparison with the bare Pd electrode. The surface coverage was 6.4 ± 0.4 × 10⁻¹⁰ mol/cm². The XPS survey study for the l-cysteine modified Pd electrode exhibited the presence of sulfur on the surface. High energy resolution XPS and FT-IR indicated that the l-cysteine molecules are sulfur bonded to the Pd surface. These results suggest the modification of palladium surface by the l-cysteine amino acids.

Carbon-supported palladium nanostructures have had a recent rise in their use for ethanol oxidation applications. In this work, we present the use of unsupported palladium nanoparticles (PdNPs), synthesized by sodium borohydride chemical reduction method, for ethanol electrochemical sensing. The unsupported PdNPs were studied for ethanol oxidation in alkaline media by cyclic voltammetry, and additionally were characterized using transmission electron microscopy, and x-ray photoelectron spectroscopy. The performance of unsupported PdNP-modified glassy carbon electrodes for the electrochemical ethanol oxidation in 1.0 M potassium hydroxide (KOH) solution was studied by cyclic voltammetry. These electrochemical results demonstrated that the unsupported PdNPs have very promising catalytic activity towards the oxidation of ethanol in alkaline media with good detection performance in the concentration range of 2304 to 288 ppm (i.e., 50.00 to 6.25 mM). The detection limit and linear correlation coefficient were 49.3 ppm (1.10 mM) and 0.9998, respectively. The unsupported PdNP-modified glassy carbon electrodes presented good cyclic voltammetric stability for ethanol sensing application in alkaline media.

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.