Significant
improvements of the photocatalytic and optoelectronic
applications demand materials that exhibit finely tuned band gaps,
band edge potentials, exciton dynamics, charged states, and crystal
facets/edges that facilitate enhanced chemical reactivity. Fundamental
insights into the structure–function relationships can dictate
the synthesis requirements of these materials. Zinc oxynitride-based
materials have demonstrated excellent photocatalytic activity, and
they also present a perfect platform for tailoring the material properties
of interest. We hereby investigate lateral heterojunctions of zinc
oxynitrides toward photocatalytic and optoelectronic applications
by computationally examining their response to composition, lattice
strain, and anion vacancy defect variation. Along with tuning the
band gap of the materials toward optimal optical performance, we demonstrated
the site specificity of the vacancy defects. Oxygen vacancies and
nitrogen vacancies were found to be favored at the bulk and at the
interface, respectively. Biaxial and vertical compressive strain increased
the band gap, whereas tensile strain reduced the band gap. The neutral
and charged vacancies rendered either increased electronic density
of states at the conduction and valence band edges or the formation
of mid-gap states. These insights into electronic state variation
via intrinsic material parameters are fundamental toward synthesis
of future materials for enhanced photocatalysis and optoelectronic
purposes.
Metal oxynitrides show promising activity for photocatalytic solar water splitting and CO2 reduction under solar irradiance even in the absence of noble metals.
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