Structural distortion of g-C3N4 induced by a schiff base reaction for efficient photocatalytic H2 evolution.

Photocatalytic H2 evolution by water splitting is a promising approach to address the challenges of environmental pollution and energy scarcity. Graphitic carbon nitride (g-C3N4) has emerged as a star photocatalyst because of its numerous advantages. To address the limitations of traditional g-C3N4, namely its inadequate visible light response and rapid recombination of photogenerated carriers, we employed a schiff base reaction to synthesize -C=N- doped g-C3N4. The introduction of -C=N- groups at the bridging nitrogen sites induced structural distortion in g-C3N4, facilitating n-π* electronic transitions from the lone pair electrons of nitrogen atom and extending light absorption up to 600 nm. Moreover, the presence of heterogeneous π-conjugated electron distribution effectively traps photogenerated electrons and enhances charge carrier separation. Benefiting from its expanded spectral response range, unique electronic properties, increased specific surface area, the doped g-C3N4 exhibited outstanding photocatalytic H2 evolution performance of 1050.13 µmol/g/h. The value was 5.9 times greater than the pristine g-C3N4.

K-N Bridge-Mediated charge separation in hollow g-C3N4 Frameworks: A bifunctional photocatalysts towards efficient H2 and H2O2 production.

The development of bifunctional photocatalysts for enhancing hydrogen (H2) and hydrogen peroxide (H2O2) production from water is essential in addressing environmental and energy issues. However, the practical implementation of photocatalytic technology is still constrained by the inadequate separation of photo-generated charge carriers. Herein, potassium (K) atoms are introduced into the interlayers of graphitic carbon nitride (g-C3N4) with a hollow hexagonal structure (K-TCN) and are coordinated with N atoms in adjacent layers. The presence of K-N coordination serves as a layer bridge, facilitating the separation of charge carriers. The hollow hexagonal structure reduces the distance over which photogenerated electrons migrate to the surface, thereby enhancing the reaction kinetics. Consequently, the optimized K-TCN exhibits a dramatically improved photocatalytic H2 (941.6 µmol g-1h-1 with platinum (Pt) as the cocatalyst) and H2O2 (347.6 µmol g-1h-1) generation as compared to hollow g-C3N4 (TCN) and bulk g-C3N4 nanosheet (CN) without K-N bridge under visible light irradiation. The unique design holds promising potential for developing highly efficient bifunctional photocatalysts towards producing renewable fuels and value-added chemicals.

Achieving high carrier separation over Bi4O5I2through Ni doping for improved photocatalytic CO2reduction.

Photocatalytic CO2reduction is considered to be an appealing way of alleviating environmental pollution and energy shortages simultaneously under mild condition. However, the activity is greatly limited by the poor separation of the photogenerated carriers. Ion doping is a feasible strategy to facilitate the charge transfer. In this work, Ni-doped Bi4O5I2photocatalyst is successfully fabricated using a one-pot hydrothermal method. A few doping levels appear in the energy band of Bi4O5I2after Ni doping, which are used as springboards for electrons transition, thus promoting photoexcited electrons and holes separation. As a consequence, a remarkably enhanced yield of CO and CH4(6.2 and 1.9µmol g-1h-1) is obtained over the optimized Bi4O5I2-Ni15, which is approximately 2.1 and 3.8 times superior to pure Bi4O5I2, respectively. This work may serve as a model for the subsequent research of Bi-based photocatalysts to implement high-performance CO2photoreduction.

Synergy of MoO2 with Pt as Unilateral Dual Cocatalyst for Improving Photocatalytic Hydrogen Evolution over g-C3 N4.

Pt is usually used as cocatalyst for g-C3 N4 to produce H2 by photocatalytic splitting of water. However, the photocatalytic performance is still limited by the fast recombination of photo-generated electrons and holes, as well as the poor absorption of visible light. In this work, MoO2 /g-C3 N4 composites were prepared, in which MoO2 synergetic with Pt photo-deposited during H2 evolution reaction worked as unilateral dual cocatalyst to improve the photocatalytic activity. Within 4 hours of irradiation, the hydrogen production rate of MoO2 -Pt dual cocatalyst modified g-C3 N4 reached 3804.89 µmol/g/h, which was 120.18 times of that of pure g-C3 N4 (GCN, 31.66 µmol/g/h), 10.98 times of that of MoO2 modified g-C3 N4 (346.39 µmol/g/h), and 9.18 times of that of Pt modified g-C3 N4 (413.64 µmol/g/h). Characterization results demonstrate that the deficient MoO2 not only promoted visible light absorption of g-C3 N4 , but also worked as a "electron pool" to capture and transfer electrons to Pt.

Filling Polyoxoanions into MIL-101(Fe) for Adsorption of Organic Pollutants with Facile and Complete Visible Light Photocatalytic Decomposition.

Transition metal-substituted polyoxometalates (POMs) were filled into a metal-organic framework (MOF) to construct a series of POM@MOF composites (PMo12O40@MIL-101, PMo11VO40@MIL-101, PMo10V2O40@MIL-101). The composite materials possess ultra-high adsorption ability, especially for PMo10V2O40@MIL-101, with an adsorption capacity of 912.5 mg·g-1 for cationic antibiotic tetracycline in wastewater, much higher than that of isolated MIL-101(Fe) and the commonly used adsorption materials, such as activated carbon and graphene oxide. In particular, they can be used as efficient photocatalysts for the photodegradation of antibiotics under visible light irradiation. The complete photodegradation of the adsorbed species can induce the facile reusability of these composites for multiple cycles. This work opens an avenue to introduce POMs into an MOF matrix for the simultaneous adsorption and photodegradation of antibiotics.

Bismuth-Based Photocatalysts for Solar Photocatalytic Carbon Dioxide Conversion.

Photocatalytic CO2 conversion into solar fuels is an effective means for simultaneously solving both the greenhouse effect and energy crisis. In the past ten years, bismuth-based photocatalysts for environmental remediation have experienced a golden period of development. However, solar photocatalytic CO2 conversion has only been developed over the past five years and, until now, no reviews have been published on bismuth-based photocatalysts for the photocatalytic conversion of CO2 . For the first time, solar photocatalytic CO2 conversion systems are reviewed herein. Synthetic methods and photocatalytic CO2 performances of bismuth-based photocatalysts, including Sillén-structured BiOX (X=Cl, Br, I); Aurivillius-structured Bi2 MO6 (M=Mo, W); and Scheelite-structured BiVO4 , Bi2 S3 , BiYO3 , and BiOIO3 , are summarized. In addition, activity-enhancing strategies for this photocatalyst family, including oxygen vacancies, bismuth-rich strategy, facet control, conventional type II heterojunction, Z-scheme heterojunction, and cocatalyst deposition, are reviewed. Finally, the main mechanistic research methods, such as in situ FTIR spectroscopy and theoretical calculations, are presented. Challenges and research trends reported in studies of bismuth-based photocatalysts for photocatalytic CO2 conversion are discussed and summarized.

Oxygen Vacancy Engineering of Bi24 O31 Cl10 for Boosted Photocatalytic CO2 Conversion.

Unearthing an ideal model to describe the role of defect sites for boosting photocatalytic CO2 reduction is rational and necessary, but it still remains a significant challenge. Herein, oxygen vacancies are introduced on the surface of Bi24 O31 Cl10 photocatalyst (Bi24 O31 Cl10 -OV) for fine-tuning the photocatalytic efficiency. The formation of oxygen vacancies leads to a new donor level near the conduction band minimum, which enables a faster charge transfer and higher carrier density. Moreover, oxygen vacancies can considerably reduce the energy for the formation of COOH* intermediates during CO2 conversion. As a result, the activity of Bi24 O31 Cl10 -OV for selective photoreduction of CO2 to CO is significantly improved, with a CO generation rate of 0.9 µmol h-1 g-1 , which is nearly 4 times higher than that of pristine Bi24 O31 Cl10 . This study reinforces our understanding of defect engineering in Bi-based photocatalysts and underscores the potential importance of implanting oxygen vacancies as an effective strategy for solar energy conversion.

Photocatalytic Mechanism Regulation of Bismuth Oxyhalogen via Changing Atomic Assembly Method.

Exciton and carrier photocatalytic processes have been proved in bismuth oxyhalogen photocatalysts. But, there are no reports about how to regulate the different mechanisms to improve photocatalytic activity for different reaction. Here, we found that the photocatalytic mechanisms could be regulated by changing the assembly method of bismuth, oxygen, and halogen atoms. Reactive oxygen species (ROS) experimentals results concluded that solid solution BiOBr0.5I0.5 showed enhanced exciton photocatalytic process, and coupling 0.5BiOBr/0.5BiOI displayed improved carrier photocatalytic proces. This work promoted the understanding about solid solution and coupling for bismuth oxyhalogen.

Noble-metal loading reverses temperature dependent photocatalytic hydrogen generation in methanol-water solutions.

Co-catalysts and sacrificing reagents are important components in artificial photocatalytic processes. Here we demonstrate that noble-metal loading reverses the temperature dependent photocatalytic activity trends of photocatalytic hydrogen (H2) generation with methanol as a sacrificing reagent. This finding suggested that visible and infrared light can enhance photocatalytic H2 generation via a heat effect over noble-metal/photocatalysts.

Synthesis of BiOI@(BiO)2CO3 facet coupling heterostructures toward efficient visible-light photocatalytic properties.

In this paper, BiOI@(BiO)2CO3 facet coupling heterostructures were synthesized via exfoliation and ion exchange, and characterized by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectra and valence-band XPS spectra. With the reaction time increasing, more BiOI can be transformed to (BiO)2CO3, and BiOI@(BiO)2CO3 facet coupling heterostructures were obtained. The photocatalytic results showed that BiOI@(BiO)2CO3 displays much higher photocatalytic activity than BiOI and (BiO)2CO3 under visible-light. The photocatalytic mechanism study revealed that BiOI@(BiO)2CO3 has strong adsorption for RhB molecules due to the ultrathin nanosheets and higher BET, and displays better separation efficiency of photoinduced charge carriers and higher photocurrent due to the {001}/{001} facet coupling.