Toward Informed Design of Nanomaterials: A Mechanistic Analysis of Structure–Property–Function Relationships for Faceted Nanoscale Metal Oxides

Nanoscale
metal oxides (NMOs) have found wide-scale applicability
in a variety of environmental fields, particularly catalysis, gas
sensing, and sorption. Facet engineering, or controlled exposure of
a particular crystal plane, has been established as an advantageous
approach to enabling enhanced functionality of NMOs. However, the
underlying mechanisms that give rise to this improved performance
are often not systematically examined, leading to an insufficient
understanding of NMO facet reactivity. This critical review details
the unique electronic and structural characteristics of commonly studied
NMO facets and further correlates these characteristics to the principal
mechanisms that govern performance in various catalytic, gas sensing,
and contaminant removal applications. General trends of facet-dependent
behavior are established for each of the NMO compositions, and selected
case studies for extensions of facet-dependent behavior, such as mixed
metals, mixed-metal oxides, and mixed facets, are discussed. Key conclusions
about facet reactivity, confounding variables that tend to obfuscate
them, and opportunities to deepen structure–property–function
understanding are detailed to encourage rational, informed design
of NMOs for the intended application.