Surface engraving engineering of polyhedral photocatalysts

Polyhedral micro-/nanocrystals are important and charming members of photocatalysts, which have been extensively investigated to reveal the crystal facet-dependent property in the past decades. The photocatalytic activity of polyhedral photocatalysts is strongly determined by the geometrical configuration with different exposed surfaces, including smooth and engraved surfaces. Previous review articles have mainly highlighted the progress made in polyhedral micro-/nanocrystals exhibiting smooth surfaces. However, engraved surfaces could exhibit unique physicochemical properties compared with smooth surfaces; especially, photocatalysts with new defects (such as atomic edges, steps and kinks) and higher surface areas can be constructed by surface engraving engineering for improved charge carrier separation as well as enriched active sites. Therefore, understanding the basic theory and research advances made in surface engraving engineering of polyhedral micro-/nanocrystals is imperative for designing novel photocatalysts. So far, there is still no specialized overview on the surface engraving engineering of polyhedral photocatalysts. In this review, some typical polyhedral photocatalysts enclosed by engraved surfaces are selected as case studies for elucidating the surface engraving engineering. The synthetic strategies and engraved surface-dependent photocatalytic mechanisms are emphasized. Also, some challenges and perspectives are proposed. Hopefully, this article will be a useful guideline for the scientific researchers currently focusing on the surface engineering of polyhedral photocatalysts.