Anja Hofmann1,Roland Marschall1
University of Bayreuth1
Anja Hofmann1,Roland Marschall1
University of Bayreuth1
In times of ever-growing energy demand, the finiteness of fossil carbon reserves, and the rise in CO<sub>2</sub> emissions, solar-light induced photocatalytic water splitting for the generation of clean and renewable hydrogen as an alternative energy carrier becomes increasingly important. For this, photocatalysts with suitable band positions for solar water splitting and with high absorption of light in the visible light range are crucial. One promising candidate for this is BaNbO<sub>2</sub>N with an absorption edge up to 740 nm and suitable band positions.[1-4] Nanostructuring can be used to further enhance the photocatalytic activity by an increase of the surface area and presumably the number of reaction sites in the photocatalysis.<br/>Herein, we are presenting a novel approach for complex nanostructured oxynitrides.[5] (111)-layered perovskite Ba<sub>5</sub>Nb<sub>4</sub>O<sub>15</sub> nanofibers with tailored fiber diameter were prepared <i>via </i>electrospinning and subsequent calcination, [6-8] and were then converted to cubic perovskite oxynitride nanofibers by ammonolysis.[5] Most importantly, the nanofiber morphology retains during the ammonolysis, and the nanofiber diameter can be tailored as well. A thorough characterization including Rietveld refinement revealed the formation of a novel BaNbO<sub>2</sub>N-Ba<sub>2</sub>NbO<sub>3</sub>N oxynitride composite. The conversion resulted in visible-light absorption with a decrease of the band gap from 3.9 eV for the Ba<sub>5</sub>Nb<sub>4</sub>O<sub>15 </sub>layered perovskite nanofibers to 1.9 eV for the converted oxynitride nanofibers. Diameter-dependent hydrogen and oxygen evolution activities of the converted oxynitride nanofibers decorated with Pt or CoNbO<sub>4</sub>, respectively, with an optimum nanofiber diameter will be presented.<br/><br/>[1] T. Hisatomi <i>et al., Energy Environ. Sci., </i><b>2013</b>, <i>6</i>, 3595.<br/>[2] M. Hojamberdiev <i>et al., J. Mater. Chem. A, </i><b>2016</b>, <i>4</i>, 12807.<br/>[3] T. Yamada <i>et al., J. Phys. Chem. C, </i><b>2018</b>, <i>122</i>, 8037.<br/>[4] J. Seo <i>et al., Adv. Energy Mater., </i><b>2018</b>, <i>8</i>, 1800094.<br/>[5] A. Hofmann <i>et al.</i>, <i>Adv. Mater. Interfaces</i>, 2021, 2100813.<br/>[6] N. C. Hildebrandt <i>et al., Small, </i><b>2015</b>, <i>11</i>, 2051.<br/>[7] A. Bloesser <i>et al., J. Mater. Chem. A, </i><b>2018</b>, <i>6</i>, 1971.<br/>[8] A. Bloesser <i>et al. ACS Appl. Energy Mater. </i><b>2018</b>, <i>1</i>, 2520.