Enhanced electrocatalytic effects of Pd particles immobilized on GC surface on the nitrite oxidation reactions

Abstract

Nitrite (NO 2− ) oxidation reactions (NOR) have been performed using a pristine glassy carbon (GC) electrode and Pd modified GC electrode to investigate catalysis and kinetics of oxidation reaction. The XPS analysis revealed that Pd nanoparticles (NPs) on GC is differed electronically from Pd particles alone. Electrochemical observations entailed that the Pd-GC electrode improved the catalytic efficiency by lowering peak potential and improving peak current compared to those obtained by GC or Pd electrode alone. Additionally, the onset potential (E i ) of kinetic process concerning NOR was appeared at 0.63 V for Pd-GC electrode which is smaller than 0.81 V and 0.75 V observed by GC and Pd electrodes, respectively. These observations suggest that the Pd–GC electrode can obtain faster electron transfer and maximum catalytic sites. The validation of Pd-GC as noble catalyst is also supported by observing least free energy of activation at peak (ΔG p‡ = 0.461 eV). The nitrite ions involve a single electron transfer reaction with NO 2 molecules being the product, which later undergoes through a dispropornation reaction yielding NO 2− and NO 3− as final products. The precise observations by RDE experiments revealed that the charge transfer reaction followed by an irreversible first order kinetics with standard rate constant (k 0 ) of 1.98 × 10 −4 cm/s and formal potential (E o ′ ) of 0.03 V.