Estudo da reação de redução do oxigênio em matriz de carbono XE2B modificado com átomos de O, N, S e P para eletrogeração de H>sub<2>/sub<O>sub<2>/sub<>i< in situ>/i<

Abstract

Hydrogen peroxide (H2O2) is an important oxidizing agent used in many industrial and domestic processes and in wastewater treatment. When produced on an industrial scale, it presents serious logistical and safety constraints related to its handling and storage. In this context, the development and feasibility of new technologies capable of generating H2O2 close to where it will be consumed has become increasingly necessary. As a promising alternative, the electrosynthesis of H2O2 at adjustable concentrations through the selective oxygen reduction reaction (ORR) has received enormous attention in recent years. In this regard, the present study aimed to produce new electrocatalyst materials for in situ electrogenation of H2O2 from the functionalization of commercially available carbonaceous material (Printex XE2B carbon. The XE2B carbon was modified using the hydrothermal chemical doping technique and co-doping with the elements N, O, S and/or P. The newly produced electrocatalysts were physicochemically characterized using CNHS/O elemental analysis, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (MET), Contact Angle, X-ray Excited Photoelectron (XPS) and Raman spectroscopy techniques. The catalyst activity and selectivity for H2O2 production exhibited by the synthesized materials were investigated by cyclic voltammetry and linear scanning voltammetry techniques using rotating ring disc electrodes (RRDE) and gaseous diffusion electrodes (EDG). Of the materials studied, the N/XE2B catalyst showed high efficiency for H2O2 production compared to XE2B, O/XE2B, N,S/XE2B and N,P/XE2B. The selectivity of N/XE2B was 94% for H2O2 electrogenation exhibiting better activity in terms of potentials with onset to RRO of 560 mV compared to XE2B (SH2O2~80%) for hydrogen peroxide production. Other results quite relevant to the study were obtained by applying XE2B* (no change), XE2B and N/XE2B materials for the generation of H2O2 from the use of the gaseous diffusion electrode (EDG). The results obtained after the electrolysis time of 180 min reflected for the following order of efficiency: N/XE2B > XE2B* > XE2B. In view of the increased catalytic efficiency for H2O2 in situ using EDG it can be stated that the expressive results for the synthesized N/XE2B catalyst, demonstrated high efficiency for H2O2 production and good performance for RRO selectivity via 2e -.