Photo-generation of cyclic carbonates using hyper-branched Ru-TiO2

Atomically Dispersed Metal Catalysts for the Conversion of CO2 into High-Value C2+ Chemicals

The conversion of carbon dioxide (CO2) into value-added chemicals with two or more carbons (C2+) is a promising strategy that cannot only mitigate anthropogenic CO2 emissions but also reduce the excessive dependence on fossil feedstocks. In recent years, atomically dispersed metal catalysts (ADCs), including single-atom catalysts (SACs), dual-atom catalysts (DACs), and single-cluster catalysts (SCCs), emerged as attractive candidates for CO2 fixation reactions due to their unique properties, such as the maximum utilization of active sites, tunable electronic structure, the efficient elucidation of catalytic mechanism, etc. This review provides an overview of significant progress in the synthesis and characterization of ADCs utilized in photocatalytic, electrocatalytic, and thermocatalytic conversion of CO2 toward high-value C2+ compounds. To provide insights for designing efficient ADCs toward the C2+ chemical synthesis originating from CO2, the key factors that influence the catalytic activity and selectivity are highlighted. Finally, the relevant challenges and opportunities are discussed to inspire new ideas for the generation of CO2-based C2+ products over ADCs.

Core-shell TiO2-x-CuyO microspheres for photogeneration of cyclic carbonates under simulated sunlight

Propylene carbonates are important organic solvents and feedstocks for different applications, including synthesis of polymers and Li-batteries. The generation of propylene carbonate utilising anthropogenic CO₂ and renewable solar energy offers an alternative sustainable process with a closed loop carbon cycle. The development of microstructured photocatalysts with desired properties, including high degree of product selectivity, wide range of optical properties, and maximised conversion yield, plays an important role for effective production of propylene carbonate from CO₂. A hierachical hollow core with a double shell of TiO_2-x-Cu₂O-CuO was fabricated using the versatile solvothermal-microwave synthesis method. The fabricated sample revealed effective cascading of photogenerated electrons and holes that promoted the conversion of propylene carbonate (i.e., 1.6 wt%) under 1 Sun irradiation.

Hierarchical hyper-branched titania nanorods with tuneable selectivity for CO2 photoreduction

Utilising captured CO₂ and converting it into solar fuels can be extremely beneficial in reducing the constantly rising CO₂ concentration in the atmosphere while simultaneously addressing energy crisis issues. Hence, many researchers have focused their work on the CO₂ photoreduction reaction for the last 4 decades. Herein, the titania hyper-branched nanorod (HBN) thin films, with a novel hierarchical dendritic morphology, revealed enhanced CO₂ photoreduction performance. The HBNs exhibited enhanced photogenerated charge production (66%), in comparison with P25 (39%), due to the unique hyper-branched morphology. Furthermore, the proposed HBN thin films exhibited a high degree of control over the product selectivity, by undergoing a facile phase-altering treatment. The selectivity was shifted from 91% towards CO, to 67% towards CH₄. Additionally, the HBN samples showed the potential to surpass the conversion rates of the benchmark P25 TiO₂ in both CO and CH₄ production. To further enhance the selectivity and overall performance of the HBNs, RuO₂ was incorporated into the synthesis, which enhanced the CH₄ selectivity from 67% to 74%; whereas the incorporation of CuO revealed a selectivity profile comparative to P25.

The use of hierarchical 1–3D Hyper-Branched Nanorods (HBNs) is examined as a photocatalyst for CO₂ photoreduction, utilising a facile protonation treatment able to tune the selectivity of CO₂ photoreduction products between (91%) CO to (67%) CH₄.

Highly selective visible-light-triggered CO2 fixation to cyclic carbonates under mild conditions using TiO2/multiwall carbon nanotubes (MWCNT) grafted with Pt or Pd nanoparticles

Visible light-induced CO2 fixation to cyclic carbonates catalyzed by Pd//TiO2/MWCNT photocatalyst.