Using black carbon modified with NbMo and NbPd oxide nanoparticles for the improvement of H2O2 electrosynthesis

Oxygen reduction reaction (ORR) is an important reaction with applications in advanced oxidative processes through in aim hydrogen peroxide electrogeneration. Oxygen can be reduced either to hydrogen peroxide via two-electron pathway or in a competitive way to water via four-electron pathway. This study shows the application of Printex L6 carbon modified with niobium/molybdenum or niobium/palladium oxides for H2O2 generation in K2SO4 0.1 mol L-1 (pH 2), where the modified carbon contributed to an increase in electroconductivity compared to unmodified carbon. The catalysts were prepared by the polymeric precursor method and were analyzed by x-ray absorption near edge structure (XANES), x-ray diffraction (XRD), and xray photoelectron spectroscopy (XPS) which showed the presence of orthorhombic Nb2O5 and MoO3 and tetragonal PdO independent phases. Also, the data obtained from x-ray fluorescence (FRX) and transmission electron microscopy (TEM) showed particle size of about 5 nm for the modified Printex L6 carbon compared to 25-30 nm for the unmodified Printex L6 carbon in an almost homogeneous distribution on the carbon surface. Based on the electrochemical analyses, the values obtained for H2O2 selectivity were 77, 77 and 88% for 5% Nb50Mo50/C, 5%Nb90Pd10/C, and 5% Nb95Pd05/C, respectively, compared to 89% for unmodified Printex L6 carbon. The materials investigated presented potential shifts of 110, 420 and 340 mV for 5% Nb50Mo50/C, 5% Nb-90 Pd-10/C and 5% Nb95Pd05 /C, respectively, compared to Printex L6 carbon at a determined current density.