Synthesis of Layered Double Hydroxides and TiO2 Supported Metal Nanoparticles for Electrocatalysis

In the present work, solution-phase synthesis was employed to prepare two sets of catalysts with different transition metals as active sites. One set contained Au or Pd supported on TiO2 (Au-TiO2, Pd-TiO2), whereas the other set contained layered double hydroxides (NiFe-LDH and CuFe-LDH). The electrocatalytic performance of these composite materials was investigated by cyclic voltammetry (CV) using a model compound 4-nitrophenol (4-NP). Composite materials were characterized by various analytical techniques to gain insight into the catalysts active sites. The morphology and structure of the prepared samples were investigated by X-ray diffraction, attenuated total reflectance Fourier transform infrared, X-ray photoelectron spectroscopy, transmission scanning electron microscope, and field emission scanning electron microscope. Metal nanoparticles loading on TiO2 was measured by inductively coupled plasma - optical emission spectrometry. CV measurements were performed in acetonitrile solution containing 0.1 m tetrabutylammonium hexafluorophosphate (TBAPF(6)) and 1 mm 4-NP. Among all dioxides (Au-TiO2, Pd-TiO2) and hydroxides (NiFe-LDH and CuFe-LDH) studied, Pd-TiO2 shows the lowest onset potential (-0.32 V vs. Ag/AgCl) for the electrocatalytic reduction of 4-NP. This is the first comparative study of such materials for 4-NP electrocatalysis in aprotic solvent, thus demonstrating the suitability of dioxide and hydroxide based materials as electrocatalysts.