Cobalt Oxide Nanoclusters on Rutile Titania as Bifunctional Units for Water Oxidation Catalysis and Visible Light Absorption: Understanding the Structure–Activity Relationship

Abstract

The structure of cobalt oxide (CoO) nanoparticles dispersed on rutile TiO (R-TiO) was characterized by X-ray diffraction, UV-vis-NIR diffuse reflectance spectroscopy, high-resolution transmission electron microscopy, X-ray absorption fine-structure spectroscopy, and X-ray photoelectron spectroscopy. The CoO nanoparticles were loaded onto R-TiO by an impregnation method from an aqueous solution containing Co(NO)·6HO followed by heating in air. Modification of the R-TiO with 2.0 wt % Co followed by heating at 423 K for 1 h resulted in the highest photocatalytic activity with good reproducibility. Structural analyses revealed that the activity of this photocatalyst depended strongly on the generation of CoO nanoclusters with an optimal distribution. These nanoclusters are thought to interact with the R-TiO surface, resulting in visible light absorption and active sites for water oxidation.

Water Splitting on Rutile TiO2‐Based Photocatalysts

“…[98] Modification of rutile TiO 2 with 2.0 wt %c obalt followedb yh eating at 423 Kf or 1hresulted in the highest photocatalytic activity,w hichw as higher than an analogousm aterialo ptimally modified with Co(OH) 2 .P hysicochemicala nalyses indicated that the activity of this photocatalyst was dependent on the formation of Co 3 O 4 nanoclusters with an optimal distribution. [98] Modification of rutile TiO 2 with 2.0 wt %c obalt followedb yh eating at 423 Kf or 1hresulted in the highest photocatalytic activity,w hichw as higher than an analogousm aterialo ptimally modified with Co(OH) 2 .P hysicochemicala nalyses indicated that the activity of this photocatalyst was dependent on the formation of Co 3 O 4 nanoclusters with an optimal distribution.…”

“…Then, the structure of cobalt oxide nanoparticles, which were loaded on the rutile TiO 2 surfaceb ya ni mpregnation methodf rom an aqueous solution containing Co(NO 3 ) 2 ·6 H 2 O followed by heatingi na ir,w as systematically studied by meanso fX-ray diffraction, UV/Vis/NIR diffuse reflectance spectroscopy,h igh-resolution transmission electron microscopy,Xray absorption fine-structures pectroscopy,a nd X-ray photoelectrons pectroscopy. [98] Modification of rutile TiO 2 with 2.0 wt %c obalt followedb yh eating at 423 Kf or 1hresulted in the highest photocatalytic activity,w hichw as higher than an analogousm aterialo ptimally modified with Co(OH) 2 .P hysicochemicala nalyses indicated that the activity of this photocatalyst was dependent on the formation of Co 3 O 4 nanoclusters with an optimal distribution. These nanoclustersa re considered to interactw ith the TiO 2 surface, which leads to visible light absorption and activesites for water oxidation.…”

“…Maeda et al very recently reported an ew water photooxidation system constructed with rutile TiO 2 and nanoparticulate cobalt hydroxide (or oxide)t hat could oxidize water to generate O 2 under visible light irradiation up to 850 nm ( Figure 13). [97,98] Cobalt-based compounds, such as cobalt hydroxide and oxide, are known to be good catalysts for water oxidation. [25,27] In contrastt ot he typical semiconductor photocatalysis process( see Figure 1), it was suggested that electrons migrate from the Co(OH) 2 nanoclusters to the TiO 2 support after photoexcitation, andw ater oxidationo ccurs on the electron-deficient cobalt species, as illustrated in Figure 13.…”

Engineering oxygen vacancy on rutile TiO2 for efficient electron-hole separation and high solar-driven photocatalytic hydrogen evolution

“…It is well-known that TiO 2 has three different crystal phases, anatase, brookite and rutile [15]. Notably, the rutile TiO 2 has attracted great research interest due to the fact that it is the most stable phase in thermodynamics, compared to the other two crystalline phases [16][17][18]. Rutile TiO 2 is suitable for photocatalytic water splitting due to its appropriate band energy position.…”

Synthesis of Well-Defined, Surfactant-Free Co3O4 Nanoparticles: The Impact of Size and Manganese Promotion on Co3O4 Reduction and Water Oxidation Activity

“…Oxides of iridium or ruthenium are known to be effective in water oxidations, 41 however more recently cobalt oxide has been found to be an effective low cost catalyst. 43,44,45,46,47 In addition, MnOx species has been reported to enhance the water oxidation ability of cobalt oxide. 48,49,50 We therefore investigated first the effect of particle size of cobalt oxide and further the presence of Mn on water oxidation ability of Co3O4.…”