Stabilization and Activation of Pd Nanoparticles for Efficient CO2-Reduction: Importance of their Generation within Supramolecular Network of Tridentate Schiff-Base Ligands with N,N Coordination Sites

Abstract Tridentate Schiff base ligand L (L = C14H12N2O3) reacts with palladium(II) chloride, to give a complex of formula [Pd(C14H12N2O3)Cl2]2∙MeOH. The spectroscopic, microanalytical and X-ray crystallographic data are consistent with the view that palladium(II) ion is coordinated by two nitrogen donor atoms, with typical PdII-N distances and two chloride ligands, representing thus N,N instead of possible N,N,O coordination mode. The reduced Pd° catalytic sites are electrochemically generated (by voltammetric potential cycling) within the film of supramolecular network of tridentate Schiff base ligands. The IR and XPS data of the electroreduced material are consistent with the existence of interactions between the palladium catalytic centers and the network of supramolecular ligands with N,N coordination sites. In comparison to conventional Pd nanoparticles, the CO2-reduction current densities, which have been recorded in near-neutral KHCO3 both under voltammetric and chronoamperometric conditions and normalized against electrochemically active surface area of palladium catalyst, are significantly higher at the supramolecular-ligand-supported Pd nanoparticles.