@article{hamilton_o'donnell_zoellner_sullivan_maggard_2020, title={Flux‐mediated synthesis and photocatalytic activity of NaNbO
            3
            particles}, volume={103}, ISSN={0002-7820 1551-2916}, url={http://dx.doi.org/10.1111/jace.16765}, DOI={10.1111/jace.16765}, abstractNote={Abstract Using molten‐salt synthetic techniques, NaNbO 3 (Space group Pbcm ; No. 57) was prepared in high purity at a reaction time of 12 hours and a temperature of 900°C. All NaNbO 3 products were prepared from stoichiometric ratios of Nb 2 O 5 and Na 2 CO 3 together with the addition of a salt flux introduced at a 10:1 molar ratio of salt to NaNbO 3 , that is, using the Na 2 SO 4 , NaF, NaCl, and NaBr salts. A solid‐state synthesis was performed in the absence of a molten salt to serve as a control. The reaction products were all found to be phase pure through powder X‐ray diffraction, for example, with refined lattice constants of a = 5.512(5) Å, b = 5.567(3) Å, and c = 15.516(8) Å from the Na 2 SO 4 salt reaction. The products were characterized using UV‐Vis diffuse reflectance spectroscopy to have a bandgap size of ~3.5 eV. The particles sizes were analyzed by scanning electron microscopy (SEM) and found to be dependent upon the flux type used, from ~<1 μm to >10 μm in length, with overall surface areas that could be varied from 0.66 m 2 /g (for NaF) to 1.55 m 2 /g (for NaBr). Cubic‐shaped particle morphologies were observed for the metal halide salts with the set of exposed (100)/(010)/(001) crystal facets, while a truncated octahedral morphology formed in the sodium sulfate salt reaction with predominantly the set of (110)/(101)/(011) crystal facets. The products were found to be photocatalytically active for hydrogen production under UV‐Vis irradiation, with the aid of a 1 wt% Pt surface cocatalyst. The platinized NaNbO 3 particles were suspended in an aqueous 20% methanol solution and irradiated by UV‐Vis light ( λ > 230 nm). After 6 hours of irradiation, the average total hydrogen production varied with the particle morphologies and sizes, with 753 µmol for Na 2 SO 4 , 334 µmol for NaF, 290 µmol for NaCl, 81 µmol for NaBr, and 249 µmol for the solid‐state synthesized NaNbO 3 . These trends show a clear relationship to particle sizes, with smaller particles showing higher photocatalytic activity in the order of NaF > NaCl > NaBr. Furthermore, the particle morphologies obtained from the Na 2 SO 4 flux showed even higher photocatalytic activity, though having a relatively similar overall surface area, owing to the higher activity of the (110) crystal facets. The apparent quantum yield (100 mW/cm 2 , λ = 230 to 350 nm, pH = 7) was measured to be 3.7% for NaNbO 3 prepared using the NaF flux, but this was doubled to 6.8% when prepared using the Na 2 SO 4 flux. Thus, these results demonstrate the powerful utility of flux synthetic techniques to control particle sizes and to expose higher‐activity crystal facets to boost their photocatalytic activities for molecular hydrogen production.}, number={1}, journal={Journal of the American Ceramic Society}, publisher={Wiley}, author={Hamilton, Adam M. and O'Donnell, Shaun and Zoellner, Brandon and Sullivan, Ian and Maggard, Paul A.}, year={2020}, month={Jan}, pages={454–464} }
 @article{o'donnell_hamilton_maggard_2019, title={Fast Flux Reaction Approach for the Preparation of Sn2TiO4: Tuning Particle Sizes and Photocatalytic Properties}, volume={166}, ISSN={["1945-7111"]}, DOI={10.1149/2.0141905jes}, abstractNote={The Sn 2 TiO 4 phase is a small-bandgap (E g ∼ 1.6 eV) semiconductor with suitable band energies to drive photocatalytic water- splitting. A new fast flux reaction can be used to prepare high purity Sn 2 TiO 4 in reaction times of down to 5 minutes. Shorter reaction times (5 and 15 min) lead to nanosized particles while longer reaction times (24 hours) yield micron-sized particles. The nanoparticles show an increased bandgap size owing to quantum size effects in the weak confinement regime (r >> a B ), increasing by ∼ 0.3 eV from 1.60 eV to 1.89 eV (indirect). From Mott-Schottky analyses, the conduction band edge is found to shift to slightly more negative potentials while the valence band edge exhibits a relatively larger positive shift. Calculations show this arises from the more disperse Sn s -orbital bands at the top of the valence band, compared the large Ti-based d -orbital band at the bottom of the conduction band. The photocatalytic activities of the Sn 2 TiO 4 nanoparticles for molecular hydrogen and oxygen production showed higher rates than the equivalent micron-sized particles as a result of both higher surface areas and higher overpotentials to drive each of the half reactions.}, number={5}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={O'Donnell, Shaun and Hamilton, Adam and Maggard, Paul A.}, year={2019}, month={Jan}, pages={H3084–H3090} }