Facile solvo-combustion synthesis of crystalline NaTaO3 and its photocatalytic performance for hydrogen production

Abstract

Significant attention has been paid on the photocatalytic production of hydrogen from water splitting by using semiconductor materials. The NaTaO3 phase has been studied for this purpose due to its high potential to generate charge carriers by absorbing the photons energy. This work reports for the first time the synthesis of NaTaO3 powder through an innovative solvo-combustion reaction using the acetyl acetone as template and fuel. It can be mention some advantages of this method such as compounds with high crystallinity, large surface area and specific morphology at nanometer level under low temperature, 180°C. In order to remove organic material and increase phase crystallinity, this powder was annealed at different temperatures up to 700°C. All the reaction products were characterized and its photophysical and textural properties were determined. The XRD analysis results showed that crystalline phase of NaTaO3 is obtained from the as-prepared material at 180°C. At higher temperature, the presence of a second phase, Na2Ta4O11, was observed. The TEM micrographs revealed that NaTaO3 has hierarchical cubic morphology in the nanometer level with the formation of nanosteps between NaTaO3 particles. The materials presented high specific surface area values around 30–120m2g−1, which are twice at 180 and 600°C larger than other reported works. The UV–visible analysis shows a band gap value (Eg) around 4.0eV. It was found that there is a synergy effect between crystallinity of the phase and specific surface area that is the responsible to improve the hydrogen production around three times compared with the results obtained when the pure phase of NaTaO3 was employed. Also the presence of the second crystalline phase, Na2Ta4O11, in small concentration and the formation of nanosteps between NaTaO3 nanoparticles contributed to enhance of photoactivity of NaTaO3. Finally, when RuO2 (1wt.%) was added as co-catalyst, the efficiency of hydrogen production was increased considerably, reaching around 50mmol of H2 after 5h of reaction, which is higher than other reports in literature for this material.