Tailored Co3O4-Based Nanosystems: Toward Photocatalysts for Air Purification

Surface Modification of TiO2 by Hyper-Cross-Linked Polymers for Efficient Visible-Light-Driven Photocatalytic NO Oxidation

Solar-driven photocatalysis offers an environmentally friendly and sustainable approach for the removal of air pollutants such as nitric oxides without chemical addition. However, the low specific surface area and adsorption capacity of common photocatalysts restrict the surface reactions with NO at the ppb-level. In this study, imidazolium-based hyper-cross-linked polymer (IHP) was introduced to modify the surface of TiO₂ to construct a porous TiO₂/IHP composite photocatalyst. The as-prepared composite with hierarchical porous structure achieves a larger specific surface area as 309 m²/g than that of TiO₂ (119 m²/g). Meanwhile, the wide light absorption range of the polymer has brought about the strong visible-light absorption of the TiO₂/IHP composite. In consequence, the composite photocatalyst exhibits excellent performance toward NO oxidation at a low concentration of 600 ppb under visible-light irradiation, reaching a removal efficiency of 51.7%, while the generation of the toxic NO₂ intermediate was suppressed to less than 1 ppb. The enhanced NO adsorption and the suppressed NO₂ generation on the TiO₂/IHP surface were confirmed by in situ monitoring technology. This work demonstrates that the construction of a porous structure is an effective approach for efficient NO adsorption and photocatalytic oxidation.

Unveiling the Origin of Co3 O4 Quantum Dots for Photocatalytic Overall Water Splitting

Spinel cobalt oxide displays excellent photocatalytic performance, especially in solar driven water oxidation. However, the process of water reduction to hydrogen is considered as the Achilles' heel of solar water splitting over Co₃ O₄ owing to its low conduction band. Enhancement of the water splitting efficiency using Co₃ O₄ requires deeper insights of the carrier dynamics during water splitting process. Herein, the carrier dynamic kinetics of colloidal Co₃ O₄ quantum dots-Pt hetero-junctions is studied, which mimics the hydrogen reduction process during water splitting. It is showed that the quantum confinement effect induced by the small QD size raised the conduction band edge position of Co₃ O₄ QDs, so that the ligand-to-metal charge transfer from 2p state of oxygen to 3d state of Co²⁺ occurs, which is necessary for overall water splitting and cannot be achieved in Co₃ O₄ bulk crystals. The findings in this work provide insights of the photocatalytic mechanism of Co₃ O₄ catalysts and benefit rational design of Co₃ O₄ -based photocatalytic systems.

Dual-quantum-dots heterostructure with confined active interface for promoted photocatalytic NO abatement

Constructing heterostructure is an effective way to fabricate advanced photocatalysts. However, the catalytic performance of typical common multi-dimensional bulk heterostructure still suffers from the limited active interface and inefficient carrier migration. Herein, we successfully synthesize the SnO₂/Cs₃Bi₂I₉ dual-quantum-dots nanoheterostructure (labeled as SCX, X = 1, 2, 3) for efficiently and stably photocatalytic NO removal under visible light irradiation. The NO removal rate of SC2 is almost 8 and 17 times higher than that of the single SnO₂ and Cs₃Bi₂I₉, respectively. Moreover, the SC2 photocatalyst shows only 3 % attenuation after five consecutive cycles, demonstrating good photocatalytic stability. Systematic experimental characterization and theoretical density functional theory calculations revealed that the high activity and stability of SCX originated from the efficient charge transfer at the confined interface between SnO₂ and Cs₃Bi₂I₉ quantum dots. This work provides a new perspective for constructing innovative dual-quantum-dots nanoheterostructure and assesses their potential in photocatalytic environmental applications.