2D/2D atomic double-layer WS2/Nb2O5 shell/core nanosheets with ultrafast interfacial charge transfer for boosting photocatalytic H2 evolution

A systematic review on Nb2O5-based photocatalysts: Crystallography, synthetic methods, design strategies, and photocatalytic mechanisms

With the increasing popularity of photocatalytic technology and the highly growing issues of energy scarcity and environmental pollution, there is an increasing interest in extremely efficient photocatalytic systems. The widespread immense attention and applicability of Nb2O5 photocatalysts can be attributed to their multiple benefits, including strong redox potentials, non-toxicity, earth abundance, corrosion resistance, and efficient thermal and chemical stability. However, the large-scale application of Nb2O5 is currently impeded by the barriers of rapid recombination loss of photo-activated electron/hole pairs and the inadequacy of visible light absorption. To overcome these constraints, plentiful design strategies have been directed at modulating the morphology, electronic band structure, and optical properties of Nb2O5. The current review offers an extensive analysis of Nb2O5-based photocatalysts, with a particular emphasis on crystallography, synthetic methods, design strategies, and photocatalytic mechanisms. Finally, an outline of future research directions and challenges in developing Nb2O5-based materials with excellent photocatalytic performance is presented.

Uniform-embeddable-distributed Ni3S2 cocatalyst inside and outside a sheet-like ZnIn2S4 photocatalyst for boosting photocatalytic hydrogen evolution

The rational cocatalyst design is considered a significant route to boost the solar-energy conversion efficiency for photocatalytic H₂ generation. However, the traditional cocatalyst-loading on the surface of a photocatalyst easily leads to scarce exposed active sites induced by the agglomeration of cocatalysts and a hindrance of the light absorption of the photocatalyst, thus significantly limiting the enhancement of the photocatalytic H₂-generation performance. Herein, a new concept of uniform-embeddable-distributed cocatalysts is put forward. Consequently, uniform-embeddable-distributed cocatalysts of Ni₃S₂ were designed and constructed inside and outside of the nanosheet-like ZnIn₂S₄ photocatalyst to form a Ni₃S₂/ZnIn₂S₄ binary system (UEDNiS/ZIS). The unique uniform-embeddable-distributed Ni₃S₂ cocatalyst (UEDNiS) could provide abundant exposed active sites, facilitate the spatial separation and ordered transfer of charges inside and outside of ZnIn₂S₄ nanosheets, and reduce the hydrogen-adsorption free energy for photocatalytic H₂-generation reactions. As a result, UEDNiS/ZIS exhibited a high photocatalytic H₂-generation rate of 60 μmol h^-1 under visible-light irradiation, almost 7.8 and 2.8 times higher than pristine ZnIn₂S₄ and the traditional surface-loaded Ni₃S₂/ZnIn₂S₄ (TSLNiS/ZIS), respectively. This work represents a new cocatalyst-design approach to realize high-efficiency hydrogen evolution in binary heterostructured photocatalytic systems.

Rhombohedral/Cubic In2O3 Phase Junction Hybridized with Polymeric Carbon Nitride for Photodegradation of Organic Pollutants

In recent studies, phase junctions constructed as photocatalysts have been found to possess great prospects for organic degradation with visible light. In this study, we designed an elaborate rhombohedral corundum/cubic In₂O₃ phase junction (named MIO) combined with polymeric carbon nitride (PCN) via an in situ calcination method. The performance of the MIO/PCN composites was measured by photodegradation of Rhodamine B under LED light (λ = 420 nm) irradiation. The excellent performance of MIO/PCN could be attributed to the intimate interface contact between MIO and PCN, which provides a reliable charge transmission channel, thereby improving the separation efficiency of charge carriers. Photocatalytic degradation experiments with different quenchers were also executed. The results suggest that the superoxide anion radicals (O₂^-) and hydroxyl radicals (·OH) played the main roles in the reaction, as opposed to the other scavengers. Moreover, the stability of the MIO/PCN composites was particularly good in the four cycling photocatalytic reactions. This work illustrates that MOF-modified materials have great potential for solving environmental pollution without creating secondary pollution.

Role of p-n junction initiated mixed-dimensional 0D/2D, 1D/2D, and 2D/2D BiOX (X = Cl, Br, and I)/TiO2 nanocomposite interfaces for environmental remediation applications: A review

Nowadays, we are critically facing various environmental issues. Among these, water contamination is the foremost issue, which worsens our health and living organisms in the water. Thus, it is necessary to provide an avenue to minimize the toxic matter through the development of facile technique and harmless photocatalyst. In this review, we intended to uncover the findings associated with various 0D, 1D, and 2D nanostructures featured photocatalysts for advancements in interfacial characteristics and toxic matter degradation. In this context, we evaluated the promising mixed-dimensional 0D/2D, 1D/2D, and 2D/2D bismuth oxyhalides BiOX (X = Cl, Br, and I) integrated TiO₂ nanostructure interfaces. Tunable mixed-dimensional interfaces highlighted with higher surface area, more heterojunctions, variation in the conduction and valence band potential, narrowed band gap, and built-in electric field formation between BiOX and TiO₂, which exhibits remarkable toxic dye, heavy metals, and antibiotics degradation. Further, this review further examines insights into the charge carrier generation, separation, and shortened charge transfer path at reduced recombination. Considering the advantages of type-II, S-scheme, and Z-scheme charge transfer mechanisms in the BiOX/TiO₂, we heightened the combination of various reactive species generation. In a word, the concept of mixed-dimensional BiOX/TiO₂ heterojunction interface endows toxic matter adsorption and decomposition into useful products. Challenges and future perspectives are also provided.

3D/2D Heterojunction Fabricated from RuS2 Nanospheres Encapsulated in Polymeric Carbon Nitride Nanosheets for Selective Photocatalytic CO2 Reduction to CO

Micro/nanostructure control of heterostructures is still a challenge for achieving high efficiency and selectivity of photocatalytic CO₂ conversion. In this work, a new three-dimensiona/two-dimensional (3D/2D) heterostructure is fabricated by encapsulating RuS₂ nanospheres in the interlayer of mesoporous polymeric carbon nitride (PCN) nanosheets based on an in situ growth and polymerization strategy. The unique microstructure of the obtained 3D/2D RuS₂/PCN heterojunction can effectively improve the transfer and separation efficiency of photogenerated charge carriers, reduce the mass transfer resistance of CO₂ toward active sites, and provide a confined reaction space, thus propelling the photocatalytic CO₂ reduction to CO with high selectivity. The CO yield over the optimal 5%-RuS₂/PCN sample reaches 4.2 and 2.8 times as high as that of single PCN and RuS₂ within 4 h, respectively. Furthermore, the plausible charge transfer mechanism and CO₂ reduction path are revealed by time-dependent in situ Fourier transform infrared (FT-IR) spectra combined with photophysical, electrochemical, and photoelectrochemical techniques and density functional theory (DFT) calculations. This work develops the microstructural engineering design strategy of PCN-based heterojunctions for selective photocatalytic CO₂ fuel conversion.

PtS quantum dots/Nb2O5 nanosheets with accelerated charge transfer for boosting photocatalytic H2 production

The rapid recombination rate of charges limits the improvement of photocatalytic hydrogen evolution performance related to semiconductor photocatalysts. An effective strategy to accelerate charge separation and transfer is the design and construction of new high-efficiency cocatalysts on photocatalysts. Herein, a system of PtS quantum dots/Nb₂O₅ nanosheets (PtS/Nb₂O₅) was constructed via the in situ vapor phase (ISVP) synthesis process. The conclusions from ultrafast femtosecond-resolved TA spectroscopy indicated that the lifetime of the photogenerated charges of PtS/Nb₂O₅ (6073.75 ps) was shortened markedly in contrast to that of Nb₂O₅ (6634.05 ps), manifesting the facilitated separation and transfer of photogenerated charges caused by the quantum-dot-structured PtS cocatalyst. The enhanced charge separation and transfer capacity contributes to an excellent H₂ production rate of 182.5 μmol h^-1 for PtS/Nb₂O₅, which is up to 3.4 and 12.2 times that of Pt/Nb₂O₅ and Nb₂O₅, respectively. This work brings up new avenues for constructing unique and effective photocatalysts via the cocatalyst design.

Recent advances and challenges in 2D/2D heterojunction photocatalysts for solar fuels applications

Although photocatalytic technology has emerged as an effective means of alleviating the projected future fuel crisis by converting sunlight directly into chemical energy, no visible-light-driven, low-cost, and highly stable photocatalyst has been developed to date. Due to considerably higher interfacial contact with numerous reactive sites, effective charge transmission and separation ability, and strong redox potentials, the focus has now shifted to 2D/2D heterojunction systems, which have exhibited effective photocatalytic performance. The fundamentals of 2D/2D photocatalysis for different applications and the classification of 2D/2D materials are first explained in this paper, followed by strategies to improve the photocatalytic performance of various 2D/2D heterojunction systems. Following that, current breakthroughs in 2D/2D metal-based and metal-free heterojunction photocatalysts, as well as their applications for H₂ evolution via water splitting, CO₂ reduction, and N₂ fixation, are discussed. Finally, a brief overview of current constraints and predicted results for 2D/2D heterojunction systems is also presented. This paper lays out a strategy for developing efficient 2D/2D heterojunction photocatalysts and sophisticated technology for solar fuel applications in order to address the energy issue.