| Popis: |
Tantalum-oxy-nitridenanotubes(TaOxNyNTs) ordered in 1D were successfully synthesized through controlled anodicoxidationof metallic Ta foils followed by high-temperature annealing under NH3flow to prepare unconventional nanostructured photo-electrodes active with visible light. For the synthesis, a two-step anodization process was adopted: i) the first step inethylene glycolwith 0.33 % NH4F and 3 % H2O, ii) the second step in H2SO4(98 %) with 1 % HF and 4 % H2O, by applying different voltages and anodization times. Scanning Electron Microscopy integrated with Energy Dispersive X-rayspectroscopy(SEM-EDX) revealed the NTs length ranging from 2 to 5µm, and the inner tube diameter from 20 to 100nm, in good correlation with the synthesis parameters. The N-content (from 2.7 % to 19.1 %) was dependent on the nitridation temperature (from 500° to 900°C), and the conversion of bare Ta2O5into TaOxNystrongly influenced the absorption in the visible region with a bandgap shift from 4.0 to 2.1eV, respectively. Photo-electrochemical and catalytic performances were evaluated with chronoamperometric measurements and tests in different photo-reactions using AM 1.5G simulated sunlight: (i) degradation of methylene blue (MB), (ii) ethanol gas-phase photo-reforming and (iii) bias-assisted photoelectrochemical water splitting. The TaOxNyNTs film-type electrode obtained by nitriding at 800°C showed the highest photocurrent value (0.1mA∙cm-2), and the highest rates of MB degradation (k1of 0.0189min-1) and H2photo-production. |
