Tantalum oxynitride nanotube film arrays for unconventional nanostructured photo-electrodes active with visible light

Tantalum-oxy-nitride nanotubes (TaOxNy NTs) ordered in 1D were successfully synthesized through controlled anodic oxidation of metallic Ta foils followed by high-temperature annealing under NH3 flow to prepare unconventional nanostructured photo-electrodes active with visible light. For the synthesis, a two-step anodization process was adopted: i) first step ethylene glycol 0.33 % NH4F and 3 H2O, ii) second H2SO4 (98 %) 1 HF 4 applying different voltages times. Scanning Electron Microscopy integrated Energy Dispersive X-ray spectroscopy (SEM-EDX) revealed NTs length ranging from 2 5 µm, inner tube diameter 20 100 nm, good correlation synthesis parameters. The N-content (from 2.7 19.1 dependent on nitridation temperature 500° 900°C), conversion bare Ta2O5 into TaOxNy strongly influenced absorption region bandgap shift 4.0 2.1 eV, respectively. Photo-electrochemical catalytic performances evaluated chronoamperometric measurements tests photo-reactions using AM 1.5 G simulated sunlight: (i) degradation methylene blue (MB), (ii) ethanol gas-phase photo-reforming (iii) bias-assisted photoelectrochemical water splitting. film-type electrode obtained nitriding at 800 °C showed highest photocurrent value (0.1 mA∙cm-2), rates MB (k1 0.0189 min-1) H2 photo-production.