IMPROVED PHOTO-ELECTROCHEMICAL RESPONSE OF COMPOSITES OBTAINED FROM LAYERED g-C3N4 AND TiO2 NANOTUBE ARRAYS

Some results and recent progress from our current investigations on g-C3N4/TiNT composite semiconducting materials are reported. The investigated composites have been prepared from different nitrogen precursors such as urea (U), melamine (M) and 1:1 UM mixtures, and thin films of TiO2 nanotubes (TiNT) obtained by anodization. The heterostructures have been characterized with several complementary techniques to evidence the relation between photo-behavior and composition, and their mutual synergies. The samples have been investigated as electrocatalysts in the frame of the EU project “Oxalic acid from CO2 using electrochemistry at demonstration scale” for developing new electrochemical methodologies for converting oxalic acid (OX) to glycolic acid and other high-value C2-products. The preparation,[1] the chemical-physical (XRD), morphological (SEM), structural (XPS),[2] and functional (UV-vis DRS spectra, chronoamperometry experiments)[1,2] characterization of the g-C3N4/TiO2 composites are reported together with their application as a cathode in the electrocatalytic reduction of oxalic acid. The successful fabrication of carbon nitride materials with tunable properties depending on the composition and amount of the starting nitrogen precursor is reported. The g-C3N4/TiNT heterojunctions show enhanced photo-electrochemical properties as observed from the photocurrent measurements. Traditionally titania nanotubes (TiNT) have demonstrated their ability as electrodes for oxalic acid reduction.[3,4] Here we report an exciting example of g-C3N4/TiNT composites as novel electrode materials able to improve TiNT performances. The composites behave as selective cathodic electrodes that produce glyoxylic acid (GO) and glycolic acid (GC), two high-added-value chemicals.[5] The observed faradic efficiency (FE) for the composites follows the trend: TiNT-U6 > TiNT-M6 > TiNT-MU18. TiNT-U6 shows the best performances (FEGC = 63.7%; FEGO =15.5%; OX conversion = 61.4%) after 2h of reaction. The improved photo-electrochemical properties make these materials suitable for photoelectrocatalytic applications. Therefore, they are put forward as useful components for the further design and optimization of next-generation materials needed to address the challenging area of “solar-driven chemistry and energy”.