Exceptional Photocatalytic Activity of Ordered Mesoporous β-Bi2O3 Thin Films and Electrospun Nanofiber Mats

Herein, we report the synthesis and photocatalytic properties of novel Bi 2 O 3 nanomaterials. Cubic mesoporous films were produced by coassembly of hydrated bismuth nitrate with a poly(ethylene- co -butylene)- block -poly(ethylene oxide) diblock copolymer, referred to as KLE, while nanofiber mats were produced via electrospinning. We establish that all materials employed in this work are highly crystalline after thermal treatment and that the nanoscale order of the self-assembled samples is further retained. KLE-templated films can readily produce phase-pure β-Bi 2 O 3 with an optical band gap of about 3.4 eV. Calcination of nanofibers, by contrast, leads to the formation of a composite consisting of β-Bi 2 O 3 and trace amounts of the thermodynamically stable α-Bi 2 O 3 phase. We further show the benefits of a mesoporous morphology in heterogeneous semiconductor photocatalysis. KLE-templated β-Bi 2 O 3 films exhibit much greater photocatalytic activity than nanofiber mats and nontemplated Bi 2 O 3 films (prepared under otherwise identical conditions) as well as than KLE-templated anatase TiO 2 films on a mass normalized basis. We associate this exceptional activity with (1) the comparatively high BET surface area, which provides for a large number of adsorption sites, and (2) the high phase purity of the more catalytically active β-Bi 2 O 3 .