In Situ-Grown Island-Shaped Hollow Graphene on TaON with Spatially Separated Active Sites Achieving Enhanced Visible-Light CO2 Reduction

Core-Shell Semiconductor-Graphene Nanoarchitectures for Efficient Photocatalysis: State of the Art and Perspectives

Semiconductor photocatalysis holds great promise for renewable energy generation and environment remediation, but generally suffers from the serious drawbacks on light absorption, charge generation and transport, and structural stability that limit the performance. The core-shell semiconductor-graphene (CSSG) nanoarchitectures may address these issues due to their unique structures with exceptional physical and chemical properties. This review explores recent advances of the CSSG nanoarchitectures in the photocatalytic performance. It starts with the classification of the CSSG nanoarchitectures by the dimensionality. Then, the construction methods under internal and external driving forces were introduced and compared with each other. Afterward, the physicochemical properties and photocatalytic applications of these nanoarchitectures were discussed, with a focus on their role in photocatalysis. It ends with a summary and some perspectives on future development of the CSSG nanoarchitectures toward highly efficient photocatalysts with extensive application. By harnessing the synergistic capabilities of the CSSG architectures, we aim to address pressing environmental and energy challenges and drive scientific progress in these fields.

Nitrogen Configuration Effects on Charge Carrier Dynamics in CsPbBr3/Carbon Dots S-Scheme Heterojunction for Photocatalytic CO2 Reduction

Nitrogen-doped carbon dots (NCDs) featuring primary pyrrolic N and pyridinic N dominated configurations were prepared using hydrothermal (H-NCDs) and microwave (M-NCDs) methods, respectively. These H-NCDs and M-NCDs were subsequently applied to decorate CsPbBr3 nanocrystals (CPB NCs) individually, using a ligand-assisted reprecipitation process. Both CPB/M-NCDs and CPB/H-NCDs nanoheterostructures (NHSs) exhibited S-scheme charge transfer behavior, which enhanced their performance in photocatalytic CO2 reduction and selectivity of CO2-to-CH4 conversion, compared to pristine CPB NCs. The presence of pyrrolic N configuration at the heterojunction of CPB/H-NCDs facilitated efficient S-scheme charge transfer, leading to a remarkable 43-fold increase in photoactivity. In contrast, CPB/M-NCDs showed only a modest 3-fold enhancement in photoactivity, which was attributed to electron trapping by pyridinic N at the heterojunction. The study offers crucial insights into charge carrier dynamics within perovskite/carbon NHSs at the molecular level to advance the understanding of solar fuel generation.

In Situ Construction of CuTCPP/Bi4O5Br2 Hybrids for Improved Photocatalytic CO2 and Cr(VI) Reduction

Global warming and heavy metal pollution pose tremendous challenges to human development, and photocatalysis is considered to be an effective strategy to solve these problems. Herein, copper(II) tetra (4-carboxyphenyl) porphyrin (CuTCPP) molecules were successfully in situ loaded onto Bi4O5Br2 by a hydrothermal approach. A series of experimental results show that the light absorption capacity and photogenerated carrier separation efficiency were synchronously enhanced after the construction of CuTCPP/Bi4O5Br2 composites. Hence, the as-prepared composites possess significantly improved photocatalytic ability for both CO2 and Cr(VI) reduction. Specifically, CuTCPP/Bi4O5Br2-2 achieves a CO generation rate of 17.14 μmol g-1 under 5 h irradiation, which is twice as high as that of Bi4O5Br2 (8.57 μmol g-1). Besides, the optimized CuTCPP/Bi4O5Br2-2 also exhibits a removal rate of 61.87% for Cr(VI) within 100 min under irradiation. Furthermore, the mechanism of CO2 and Cr(VI) photoreduction was explored by in situ Fourier transform infrared spectroscopy and capture experiments, respectively. This work can be a reference toward the construction of photocatalysts with high activity for solar energy conversion.

CdO decorated CdS nanorod for enhanced photocatalytic reduction of CO2 to CO

Solar-driven CO₂ reduction into fuels and sustainable energy has attracted increasing attention around the world. However, the photoreduction efficiency remains low due to the low efficiency of separation of electron-hole pairs and high thermal stability of CO₂. In this work, we prepared a CdO decorated CdS nanorod for visible light driven CO₂ reduction. The introduction of CdO facilitates the photoinduced charge carrier separation and transfer and acts as an active site for adsorption and activation of CO₂ molecules. Compared with pristine CdS, CdO/CdS exhibits a nearly 5-fold higher CO generation rate (1.26 mmol g^-1 h^-1). In situ FT-IR experiments indicated that CO₂ reduction on CdO/CdS may follow a COOH* pathway. This study reports the pivotal effect of CdO on photogenerated carrier transfer in photocatalysis and on CO₂ adsorption, which provides a facile way to enhance photocatalytic efficiency.

Recent Advances and Perspectives of Core-Shell Nanostructured Materials for Photocatalytic CO2 Reduction

Photocatalytic CO₂ conversion into solar fuels is a promising technology to alleviate CO₂ emissions and energy crises. The development of core-shell structured photocatalysts brings many benefits to the photocatalytic CO₂ reduction process, such as high conversion efficiency, sufficient product selectivity, and endurable catalyst stability. Core-shell nanostructured materials with excellent physicochemical features take an irreplaceable position in the field of photocatalytic CO₂ reduction. In this review, the recent development of core-shell materials applied for photocatalytic reduction of CO_{2 is introduced} . First, the basic principle of photocatalytic CO₂ reduction is introduced. In detail, the classification and synthesis techniques of core-shell catalysts are discussed. Furthermore, it is also emphasized that the excellent properties of the core-shell structure can greatly improve the activity, selectivity, and stability in the process of photocatalytic CO₂ reduction. Hopefully, this paper can provide a favorable reference for the preparation of efficient photocatalysts for CO₂ reduction.

Highly enhanced heterogeneous photo-Fenton process for tetracycline degradation by Fe/SCN Fenton-like catalyst

To suppress the electron-hole recombination and enhance the electron transfer on carbon nitride, an Fe-doped porous carbon nitride catalyst (Fe/SCN) was synthesized via supramolecular self-assembly method and applied in heterogeneous Fenton activation for efficient tetracycline (TC) degradation. Various characterizations revealed that the catalyst exhibited excellent visible light capture performance and electron transfer capacity. The highest degradation efficiency and mineralization rate of TC (10 mg L^-1) were achieved under neutral condition (90.3% and 61.2%, respectively) with the leaching of Fe less than 14 μg L^-1. Free radical quenching experiments and spin-resonance spectroscopy characterizations revealed the dominating role of OH in TC degradation, and density functional theory calculation confirmed the formation of Fe-N_X and revealed the interaction between Fe sites and H₂O₂. Three possible pathways of TC degradation were proposed, and the biological inhibition test revealed the potential of Fe/SCN/H₂O₂ system to reduce environmental risks caused by TC. This work provides a new insight into the design of metal-doped heterogeneous Fenton catalyst for the efficient degradation of antibiotic contaminants in water.

Polarization-induced efficient charge separation in an electromagnetic coupling MOF for enhancing CO2 photocatalytic reduction

Rapid recombination of photogenerated carriers severely impairs the performance of photocatalysts, while polarization is an effective driving force for increasing the charge separation and hence improving the photocatalytic activity. In this work, a series of magnetoelectric-coupled layered metal-organic framework (MOF) catalysts with different Co-doped contents (denoted as Ni-MOF and Co_xNi_1-x-MOF) are fabricated with different polarities and employed as novel photocatalysts for CO₂ photocatalytic reduction reaction. Our experiments show that the highest charge separation efficiency occurs in the Co_0.1Ni_0.9-MOF sample which has a maximal polarization. This Co_0.1Ni_0.9-MOF material has a best CO₂ reduction performance of 38.74 μmol g^-1h^-1 which is at a high level in the currently reported layered materials. Meanwhile, it is found that a series of Co_xNi_1-x-MOF samples all display selectivity close to 100% for CO₂ reduction to CO, which is desirable for industrial applications. Theoretical analysis shows that Co doping alters the degree of distortion of the asymmetrical Ni-centered octahedron {NiN₂O₄} in Ni-MOF by replacing Ni due to the magnetoelectric coupling effect and Jahn-Teller effect, which results in adjustable polarity of Co_xNi_1-x-MOF. This work provides new insights on how to improve photogenerated charge separation in MOF by enhancing polarization.

Recent Progress in the Synthesis and Applications of Composite Photocatalysts: A Critical Review

Photocatalysis is an advanced technique that transforms solar energy into sustainable fuels and oxidizes pollutants via the aid of semiconductor photocatalysts. The main scientific and technological challenges for effective photocatalysis are the stability, robustness, and efficiency of semiconductor photocatalysts. For practical applications, researchers are trying to develop highly efficient and stable photocatalysts. Since the literature is highly scattered, it is urgent to write a critical review that summarizes the state-of-the-art progress in the design of a variety of semiconductor composite photocatalysts for energy and environmental applications. Herein, a comprehensive review is presented that summarizes an overview, history, mechanism, advantages, and challenges of semiconductor photocatalysis. Further, the recent advancements in the design of heterostructure photocatalysts including alloy quantum dots based composites, carbon based composites including carbon nanotubes, carbon quantum dots, graphitic carbon nitride, and graphene, covalent-organic frameworks based composites, metal based composites including metal carbides, metal halide perovskites, metal nitrides, metal oxides, metal phosphides, and metal sulfides, metal-organic frameworks based composites, plasmonic materials based composites and single atom based composites for CO₂ conversion, H₂ evolution, and pollutants oxidation are discussed elaborately. Finally, perspectives for further improvement in the design of composite materials for efficient photocatalysis are provided.

Biomass-Induced Diphasic Carbon Decoration for Carbon Nitride: Band and Electronic Engineering Targeting Efficient N2 Photofixation

Boosting the replacement of traditional NH₃ production (Haber-Bosch process) with photocatalytic technology is of great importance for energy and environment remediation. Herein, to develop a photocatalyst with efficient charge separation and abundant reactive sites for photocatalytic N₂ fixation, a biomass-induced diphase-carbon doping strategy is proposed by adding lotus root starch which can be environmentally produced into the preparation of carbon nitride (CN). The adjustment to the CN framework by planar-fused carbon optimizes the band alignment of the catalyst, improving its response to sunlight. In particular, the in-plane-fused carbon in collaboration with the physically piled carbon initiates unique dual electron transfer pathways from different dimensions. The diphasic carbons can both function as qualified reactive sites according to the experimental explorations and further theoretical calculations, which effectively regulate the electron transfer and energy barrier associated with the N₂ reduction on catalyst. The bio-carbon-doped catalyst exhibits drastically enhanced photocatalytic N₂ fixation performance, and the NH₃ yield on the optimized DC-CN0.1 reaches 167.35 µmol g^-1 h^-1 , which is fivefold of g-C₃ N₄ and stands far out from the single-phase doped systems. These explorations expand the metal-free skeleton engineering toolbox and provide new guidance for the solar energy utilizations.

In situ Irradiated XPS Investigation on S-Scheme TiO2 @ZnIn2 S4 Photocatalyst for Efficient Photocatalytic CO2 Reduction

Reasonable design of efficient hierarchical photocatalysts has gained significant attention. Herein, a step-scheme (S-scheme) core-shell TiO₂ @ZnIn₂ S₄ heterojunction is designed for photocatalytic CO₂ reduction. The optimized sample exhibits much higher CO₂ photoreduction conversion rates (the sum yield of CO, CH₃ OH, and CH₄ ) than the blank control, i.e., ZnIn₂ S₄ and TiO₂ . The improved photocatalytic performance can be attributed to the inhibited recombination of photogenerated charge carriers induced by S-scheme heterojunction. The improvement is also attributed to the large specific surface areas and abundant active sites. Meanwhile, S-scheme photogenerated charge transfer mechanism is testified by in situ irradiated X-ray photoelectron spectroscopy, work function calculation, and electron paramagnetic resonance measurements. This work provides an effective strategy for designing highly efficient heterojunction photocatalysts for conversion of solar fuels.

Line defects in plasmatic hollow copper ball boost excellent photocatalytic reaction with pure water under ultra-low CO2 concentration

By using a low CO₂ concentration as a C1 source, the design of a plasmonic catalyst that can effectively photocatalytic CO₂ reduction is of great significance for sustainable and ecological development. Herein, the space confinement effect and liquid environment of the molten salt result in uniform hollow structure, while the strong aggressive force furnished via using molten salt enhances the formation of line defects. This special structure can not only provide a large number of active sites but also greatly accelerate the transport of photoinduced charge carriers. The hollow copper ball with line defects (CCu) shows excellent photocatalytic activity with pure water (1028.57 μmol g^-1), and it also shows good catalytic activity even under ultra-low CO₂ content, which far exceeds the catalytic activity of most semiconductor-based catalysts. This work is designed to simultaneously construct line defect and hollow structure in plasmatic metal nanoparticles for efficient photocatalytic CO₂ reduction.