How insignificant modifications of photocatalysts can significantly change their photocatalytic activity

Abstract

Slight surface modifications of TiO2 (“insignificant” at first glance), such as exposing to reducing or oxidizing agents and deposition of small amounts of a semiconductor material at the surface, may strongly affect the photoactivity of materials.

TiO2 with Tunable Anatase-to-Rutile Nanoparticles Ratios: How Does the Photoactivity Depend on the Phase Composition and the Nature of Photocatalytic Reaction?

“…Second, the photocatalysts obtained upon different thermal treatments , also cannot be compared directly, since the crystallinity and crystal size are changed significantly during synthesis at different temperatures. Third, using a wide range of pH- and mixed-ion-tuned synthetic procedures, , the photoactivity can be heavily influenced by the adsorbed and admixed species and ions. , Finally, the photoactivity of different forms of photocatalysts, i.e. , powders and films, is not comparable because the access of reagents to the photocatalyst surface is completely different.…”

Spectroscopic and Spectroelectrochemical Studies on Redox Properties of Zinc Sulfide and Their Consequences on Photocatalytic Activity

“…Up to now, most measurements have shown no differences from the original ZnS(1:1), except for the emission spectra and the DOS profiles. The spectroelectrochemical method seems to be particularly sensitive to such potentially insignificant changes, as already demonstrated elsewhere . The fact that emission and DOS vary when only the surface is modified points to the same origin of these changes, i.e ., to surface states.…”

“…The spectroelectrochemical method seems to be particularly sensitive to such potentially insignificant changes, as already demonstrated elsewhere. 43 The fact that emission and DOS vary when only the surface is modified points to the same origin of these changes, i.e., to surface states. Moreover, this observation strengthens our hypothesis for using the onset potential of DOS to position our model at the potential scale.…”

On the importance of catalysis in photocatalysis: Triggering of photocatalysis at well-defined anatase TiO2 crystals through facet-specific deposition of oxygen reduction cocatalyst

“…In this context, we point out at a recent report by Macyk et al who showed how the photoactivity of TiO2 powder photocatalysts may change significantly upon supposedly insignificant modifications of surface structure, such as deposition of tiny amounts of TiO2 by few cycles of atomic layer deposition (ALD). 73 Therefore, we envisage that "gentle" surface modification methods like ALD may be leveraged for interfacial engineering of, for example, {001} facets on atomic level with high impact on photocatalytic activity. Importantly, in line with results of Mul et al 47 and Ohtani et al, 29 we found no evidence for inherently anisotropic charge transport in crystals with well-defined facets that would, rather independently from reactions occurring at the surface, drive photogenerated electrons preferentially to {101} facets and holes to {001} facets, as often suggested.…”