The design of photocatalysts using semiconductors has been intensively studied to achieve an efficient solar-to-hydrogen conversion. Ideal photocatalysts should have a bandgap that corresponds to the visible region of the solar spectrum because 50 % of the solar output is emitted in this range. Nanostructuring photocatalysts is a good approach to improve the efficiency and rate of H2 production through increasing the surface area, which creates significantly more active sites for the reaction to occur. Mesoporous nanoscale architectures are ideal motifs to achieve these high surface area materials. In this study, we have synthesized mesoporous Ta3N5 by converting sol-gel based Ta2O5 thin films to Ta3N5 via controlled ammonolysis. The bandgap of prepared Ta3N5 is estimated to be 2.1 eV from the absorption edge (~600 nm). The phase conversion from orthorhombic Ta2O5 to orthorhombic Ta3N5 is successfully characterized by GIWAXS shown Fig 1 (a). Ellipsometric porosimetry has been utilized to confirm that these thin films are comprised of an interconnected 3-D pore network. The pore sizes of Ta2O5 and Ta3N5 films are 14 nm and 17 nm in diameter, respectively. These results are calculated from the Kelvin equation and are in excellent agreement with the pore size estimated from the SEM images (Fig 1 (b) and (c)). Lastly, the photoelectrochemical water splitting has been carried out using a 300 W Xe lamp in 1M KOH solution. The mesoporous Ta3N5 catalyst shows efficient photocurrent response that is attributed to the 3-D interconnected mesoporosity.

3-D Interconnected mesoporous tantalum nitride as a novel water splitting photocatalyst

251st National Meeting (2016)

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