Reduced graphene oxide supported C3N4 nanoflakes and quantum dots as metal-free catalysts for visible light assisted CO2 reduction

Enhancing the Photocatalytic Activity of Halide Perovskite Cesium Bismuth Bromide/Hydrogen Titanate Heterostructures for Benzyl Alcohol Oxidation

Halide perovskite Cs3Bi2Br9 (CBB) has excellent potential in photocatalysis due to its promising light-harvesting properties. However, its photocatalytic performance might be limited due to the unfavorable charge carrier migration and water-induced properties, which limit the stability and photocatalytic performance. Therefore, we address this constraint in this work by synthesizing a stable halide perovskite heterojunction by introducing hydrogen titanate nanosheets (H2Ti3O7-NS, HTiO-NS). Optimizing the weight % (wt%) of CBB enables synthesizing the optimal CBB/HTiO-NS, CBHTNS heterostructure. The detailed morphology and structure characterization proved that the cubic shape of CBB is anchored on the HTiO-NS surface. The 30 wt% CBB/HTiO-NS-30 (CBHTNS-30) heterojunction showed the highest BnOH photooxidation performance with 98% conversion and 75% benzoic acid (BzA) selectivity at 2 h under blue light irradiation. Detailed optical and photoelectrochemical characterization showed that the incorporating CBB and HTiO-NS widened the range of the visible-light response and improved the ability to separate the photo-induced charge carriers. The presence of HTiO-NS has increased the oxidative properties, possibly by charge separation in the heterojunction, which facilitated the generation of superoxide and hydroxyl radicals. A possible reaction pathway for the photocatalytic oxidation of BnOH to BzH and BzA was also suggested. Furthermore, through scavenger experiments, we found that the photogenerated h+, e- and •O2- play an essential role in the BnOH photooxidation, while the •OH have a minor effect on the reaction. This work may provide a strategy for using HTiO-NS-based photocatalyst to enhance the charge carrier migration and photocatalytic performance of CBB.

Role of excited-state hydrogen bonding in CO2 photoreduction catalyzed by sodium magnesium chlorophyll

In this paper, we report a joint experimental and computational study to elaborate the mechanism for the photocatalytic CO2 reduction reaction (CO2RR). Experimental results indicate that the catalyst (sodium magnesium chlorophyll, MgChlNa2), which has a well-defined structure for calculation and understanding, can achieve the photoreduction of CO2 to CO only using water as a dispersant, without adding any photosensitizer or sacrificial agent. Subsequently, a series of structural models of the hydrogen-bonded complexes of the catalyst were constructed and outlined via utilizing density functional theory (DFT) calculations, including photophysical and photochemical processes. The results confirm that the rate-limiting step of the whole CO2RR was the intersystem crossing process. The electron and proton transfers involved in photophysical and photochemical processes are induced by hydrogen bonds in the excited states. The combination of experiments and calculations will provide an important reference for the design of high-efficiency photocatalysts in the photocatalytic CO2RR.

The Collision between g-C3 N4 and QDs in the Fields of Energy and Environment: Synergistic Effects for Efficient Photocatalysis

Recently, graphitic carbon nitride (g-C₃ N₄ ) has attracted increasing interest due to its visible light absorption, suitable energy band structure, and excellent stability. However, low specific surface area, finite visible light response range (<460 nm), and rapid photogenerated electron-hole (e^- -h⁺ ) pairs recombination of the pristine g-C₃ N₄ limit its practical applications. The small size of quantum dots (QDs) endows the properties of abundant active sites, wide absorption spectrum, and adjustable bandgap, but inevitable aggregation. Studies have confirmed that the integration of g-C₃ N₄ and QDs not only overcomes these limitations of individual component, but also successfully inherits each advantage. Encouraged by these advantages, the synthetic strategies and the fundamental of QDs/g-C₃ N₄ composites are briefly elaborated in this review. Particularly, the synergistic effects of QDs/g-C₃ N₄ composites are analyzed comprehensively, including the enhancement of the photocatalytic performance and the avoidance of aggregation. Then, the photocatalytic applications of QDs/g-C₃ N₄ composites in the fields of environment and energy are described and further combined with DFT calculation to further reveal the reaction mechanisms. Moreover, the stability and reusability of QDs/g-C₃ N₄ composites are analyzed. Finally, the future development of these composites and the solution of existing problems are prospected.

The Advance and Critical Functions of Energetic Carbon Dots in Carbon Dioxide Photo/Electroreduction Reactions

As a unique carbon-based nano material, carbon dots (CDs) have attracted great attention because of their special structures and properties, and have been widely used in various fields, such as bio-imaging technology, catalyst design, pollutant degradation, chemical analysis, clean energy development and so on. CDs are used as catalysts or cocatalysts for multiple energy conversion reactions due to their advantages of valid visible light utilization, fast transmission of charge carriers, excellent catalytic activity, and good electrical conductivity. This review first summarizes the basic structure and properties of CDs. The advance and critical functions of energetic CDs in carbon dioxide photo/electroreduction reactions are discussed in detail. Due to the excellent optical absorption, electron transfer properties and good conductivity of CDs, they can enhance catalytic activity and stability effectively. In the end, the existing problems and future development opportunities of CDs-based catalysts in CO₂ reduction reaction are proposed and outlined.

Experimental study on bone defect repair by BMSCs combined with a light-sensitive material: g-C3N4/rGO

Bone marrow mesenchymal stem cells (BMSCs), as seed cells, have played an important role in bone defect repair. However, efficiently amplifying and inducing BMSCs in vitro or vivo remains an urgent problem to be solved. Electrical stimulation has been beneficial to the proliferation and differentiation of BMSCs, but current electrical stimulation methods have a critical disadvantage in that they usually burn the skin. g-C₃N₄/rGO, a new photosensitive material, can produce photocurrent under natural light irradiation, thus reducing energy consumption. Our purpose was to explore whether this photocurrent can promote the proliferation and differentiation of BMSCs. g-C₃N₄/rGO synthesised under high temperature and pressure had negligible cytotoxicity as confirmed by methyl thiazolyl tetrazolium to BMSCs. Better osteogenesis was found in the blue light material group than in the light-shielding material group, exhibited by alizarin red staining, alkaline phosphatase activity, Western-Blot, and RT-qPCR. Animal experiments showed that the bone repair potential of the material group was significantly higher than that of the non-material group. Overall, we conclude that g-C₃N₄/rGO is a new non-toxic photosensitive material which can rapidly induce BMSCs into osteoblasts, accelerating bone regeneration and providing us with a feasible method of rapid bone repair.