Visible Light Active Ce-Doped and Cu–Ce co-doped TiO₂ Nanocrystals and Optofluidics for Clean Alcohol Production from CO₂

Abstract

Considering CO 2 as an alternative and sustainable resource, rather than as a waste to be treated, this work proposes the combination of doped TiO 2 nanocrystals with optofluidics for the continuous photoreduction of CO 2 to alcohols under ultraviolet and visible light. This approach aims at overcoming one of the major limitations of this technology, namely, current photoreactor configurations and low activity under visible light of the up-to-date photocatalysts. Ce-doped and Cu−Ce-codoped TiO 2 nanocrystals, synthesized by a simple and green hydrothermal method with different Cu and Ce contents, are used in a planar optofluidic microreactor with an enhanced surface-area-to-volume ratio, uniform light distribution, and a larger photon receiving area. The results show promising alcohol production rates when doping the photoactive TiO 2 nanocrystals with Ce, which leads to a maximum rate of 116 μmol•g −1 •h −1 for ethanol and 106 μmol•g −1 •h −1 for methanol, exceeding most of the reported values for visiblelight-driven CO 2 photoreduction to alcohol systems. It is worth noting that the system remains pseudostable for up to 6 h of continuous operation. Altogether, this work provides novel insights into the development of innovative systems for the transformation of CO 2 to alcohols under sunlight irradiation.

Constructing Cu defect band within TiO2 and supporting NiOx nanoparticles for efficient CO2 photoreduction

“…Besides, Cu is a well-known active site for the production of high value products from CO 2 reduction, such as methane, methanol, and alcohols. 13–22 This dual functionality attributed to OVs and Cu ions is pivotal for enhancing and optimizing CO 2 photoreduction activity and product selectivity. 23–25 However, the conventional construction of defective TiO 2 with OVs typically involves harsh reduction conditions, such as employing hydrogenation reactions in an H 2 atmosphere at elevated temperatures or utilizing strong reducing agents such as BH 4 − .…”

Utility of a Copper-Embedded Porous Organic Polymer for Visible-Light-Triggered Green Hydrogen Production and CO2 Reduction

“…Several semiconductor photocatalytic systems like pure titania, titania-loaded composite catalytic systems, − metal oxide-containing WO 3 , silicon carbide, silicon-doped titanium dioxide (TiO 2 ), and NiO-based InTaO 4 systems , were constructed and have been employed as light-absorbing semiconductor catalysts for efficient catalytic reduction of CO 2 to methanol. Additionally, heterogeneous catalysis plays a crucial role in organic synthesis providing a wide spectrum of important transformations (e.g., conversion of CO 2 into valuable chemicals and fuels) over decades, − and heterogeneous Cu-based catalysts are materials used in a wide range of chemical transformations. − In recent times, numerous Cu-based photo- and photoelectrocatalysts have been employed for the reduction of CO 2 and hydrogen production. − These advantageous features for efficient chemical transformations encouraged us to develop an appropriate methodology.…”