Surfactant-Free Preparation of Palladium Nanoparticles: Elucidation of Their Electrocatalytic Activity Toward Reduction of Carbon Dioxide

Abstract

The unique approach to fabrication of palladium nanoparticles by reduction of K2PdCl4 with ascorbic acid without the use of surfactants (such as polyvinylpyrrolidone) is proposed and adressed here. Capping agents and surfactants prevent agglomeration as well as make it possible to obtain nanoparticles in a narrow size range; on the other hand, their application results in the contamination of the Pd catalytic surfaces. In the present study, the resulting palladium nanoparticles have sizes on the level of 20-40 nm, and they are characterized by the presence of basic crystallographic planes such as (111) and (100). The results are supported with cyclic voltammetric studies, in addition to visualization and imaging with transmission electron microscopy and scanning electron microscopy.Electrochemical reduction is very promising and relatively simple to apply and can be carried out at ambiemnt condition, and furthermore, its utility can be facilitated changing the electrolysis conditions (e.g., the reaction products can be selectively controlled). To evaluate the catalytic properties of Pd nanocubes and hexagonal phases fabricated here, they have been uniformly dispersed onto glassy carbon electrode, and the electrochemical reduction of CO2 have been considered as the electrocatalytic probe here. Controlled potential electrolysis of CO2 was then performed at different applied potentials in the CO2-saturated 0.1 M KHCO3 solution (pH 6.8). Electrochemical measurements indicate that application of the Pd-nanocube catalyst the electrochemical reduction of CO2 results in other reaction products when compared to the performance of the Pd hexagonal catalyst.For comparison, the relationship between structural composition and electrochemical characteristics of palladium nanoparticles during the formic acid oxidation and the oxygen reduction reactions (in 0.5 M H2SO4) have also been considered here. The results are consistent with the view that the structural identity of palladium nanoparticles cannot be neglected during electrocatalystic studies and affects the systems’ overall performance.