Molecular deposition of a macrocyclic cobalt catalyst on TiO2 nanoparticles

Abstract

Hybrid photocatalysts consisting of molecular catalysts and solid-state surfaces have demonstrated great potential as robust and efficient systems in solar fuel production. Based on our prior work, we synthesized hybrid photocatalysts by depositing a macrocyclic Co(III) complex on three different TiO2 nanomaterials via a microwave method. The hybrid photocatalysts were tested in CO2 reduction and were thoroughly characterized with spectroscopic (UV-visible, FTIR and EPR) and microscopic (TEM) techniques. The presence of terminal OH groups on TiO2 surfaces was essential for the molecular deposition of catalytically active Co(III) sites. On a TiO2 material without such terminal OH groups, the Co(III) complex formed amorphous aggregates, which hindered interfacial electron transfer from photoactivated TiO2 to the surface molecular complex. EPR studies further revealed important information regarding the coordination geometry and interaction with CO2 of surface cobalt sites in the hybrid photocatalysts.

Well-defined surface catalytic sites for solar CO2reduction: heterogenized molecular catalysts and single atom catalysts

“…Based on the specific surface areas of the TiO 2 materials and elemental analysis results, surface catalyst densities were estimated to be 6–7 Co per nm 2 surface in CoX/P25 and ∼26 Co per nm 2 surface in CoX/Rutile. 88 These numbers further support our conclusion that CoX is molecularly deposited on P25. The absence of terminal –OH groups for uniform deposition of CoX on Rutile resulted in the formation of CoX in the aggregated form as observed in microscopic images.…”

Molecular catalysis of CO2 reduction: recent advances and perspectives in electrochemical and light-driven processes with selected Fe, Ni and Co aza macrocyclic and polypyridine complexes

“…Semi-conductors including carbon-based materials (graphene, carbon nitride, carbon nanotube and their derivatives) [213][214][215][216][217] as well as inorganic metal sulfides (MoS 2 , CdS, CdSe) 218,219 and metal oxides (TiO 2 and ZrO 2 ) [220][221][222][223] have been extensively used in constructing heterogeneous electro-and photocatalysts. In these catalytic systems, the semiconductor works as a photosensitizer, as co-catalyst and/or as an electronic channel.…”

Selective CO2 Reduction Catalyzed by Single Cobalt Sites on Carbon Nitride under Visible-Light Irradiation

“…The past few years witnessed increasing interest in hybrid photosynthetic systems that couple molecular catalysts with robust surfaces for solar fuel production. − Light-absorbing semiconductors, − electrode surfaces, − and other solid-state materials − have been employed as support for molecular CO 2 -reduction catalysts. Among the light-absorbing semiconductors, some have wide bandgaps, and their activation requires the use of UV irradiation that accounts for less than 5% of the solar spectrum.…”