Photoelectrocatalytic phenol oxidation employing nitrogen doped TiO2-rGO films as photoanodes

Abstract Semiconductor photoanodes based on TiO 2 have been widely studied due to their high photonic-to-electron conversion capability, high thermal and chemical stability and low cost. However, the absorption of high-energy regions and poor conductivity limits their applicability in photo(electro)chemistry and energy conversion processes. In this work, we studied how the incorporation of dopants as nitrogen and a good carrier conductor as graphene (rGO) generates a synergistic effect improving the visible-light harvesting of photoanodes and increasing charge carrier separation and mobility into the material, to produce a high oxidizing power for organic compounds oxidation in the photoanode/electrolyte interface. Nitrogen-doped rGO-modified TiO 2 photoanodes (NTG) were prepared by a sol − gel method and immobilized on stainless steel (SS) by dip-coating technique to evaluate their photoelectrocatalytic activity in the phenol oxidation. The surface of the photoanodes was characterized by FESEM-EDS, GIXRD, DRS, Raman and X-ray photoelectron spectroscopy. The photoelectrochemical properties of photoanodes were studied by photovoltammetry in 0.1 M HClO 4 (pH 1). FESEM images showed a cracked surface due to the evaporation of solvent from precursor solution. GIXRD patterns and Raman spectra exhibited the presence of anatase phase in the films. DRS spectra of NTG films displayed an absorption range between 450–560 nm, indicating the extension of the spectral response of the semiconductor to visible region. XPS spectra showed the presence of substitutional and interstitial nitrogen into the TiO 2 lattice, indicating the N-doping of TiO 2 . The photocurrent generated by the NTG electrode was higher than those of rGO-modified TiO 2 (TG) and N-doped TiO 2 (NT), associated to the generation of freecharge carriers under visible light by the presence of N, and their subsequent transport through carbon conjugated structure of added rGO to current collector. This synergistic behaviour allowed more efficient phenol degradation around 45% by using photoelectrocatalysis in comparison with other oxidation process as photolysis (1.5%) photocatalysis (21%) and electrocatalysis (24%).