In
this study, a facile microwave-assisted synthesis approach was
used to produce a series of bismuth oxyhalide photocatalysts, with
systematic changes in synthesis pH between 1 and 14 allowing control
over a broad range of material properties and characteristics. Detailed
structural and morphological investigations with powder X-ray diffraction
(PXRD), Rietveld refinements, pair distribution function (PDF) analysis,
and scanning electron microscopy (SEM) show that thin particles of
BiOCl, BiOBr, Bi24O31Cl10, and Bi24O31Br10 were selectively produced,
with progressive changes in morphology, facet dominance, and phase
as a function of pH. The impact of these changes on photocatalytic
performance was evaluated by studying the aerobic oxidation of benzylamine
to N-benzylidenebenzylamine, with all materials exhibiting
photocatalytic abilities under UV or blue light. While a combination
of material properties and characteristics influenced the photocatalytic
performance, certain factors such as surface area, facet dominance,
amorphous content, and band gap were found to have a larger impact
on the photocatalytic yield. Overall, this study demonstrates the
possibilities of phase, morphology, and performance of bismuth oxyhalide
photocatalysts over the entire pH range, produced using a fast and
facile microwave-assisted synthesis technique as an alternative to
the more widely applied hydrothermal synthesis approach. Additionally,
the detailed structural and morphological investigations of the materials
contribute to a greater understanding of bismuth oxyhalide photocatalysts
in general, while also highlighting some of the most desirable properties
for improved photocatalytic performance of these materials.