Porous TiO 2 Nanotubes with Spatially Separated Platinum and CoO x Cocatalysts Produced by Atomic Layer Deposition for Photocatalytic Hydrogen Production

Spatially Separate Center-to-Surround Radiation Structure Induced Tandem Electron Transfer Effect for Stable and Enhanced Photocatalysis

Spatially separate anchoring redox cocatalysts on the photocatalyst to shunt the charge migration paths is an effective route to regulate the charge flow. Differently, we herein introduce an artificially synthesized Sun-planet-like spatially separated center-to-surround radiation photosensitizer-cocatalyst structure to regulate electron flow in a tandem manner. A single Au sphere acts as the Sun/photosensitizer in the center, and small Pt particles scatter around as the planets/cocatalyst, both of which are fixed inside the MOF crystal. Such a structure can not only simultaneously increase the light harvesting capacity and electron migration kinetics but also optimize the electron transfer pathway to minimize the electron migration distance, so that the hot electrons generated by Au can be quickly transferred to Pt through MOF before annihilation, leading to a significant photoactivity promotion.

One-Step Decoration of Subnanometer MoOx Clusters on Bi11VO19 Nanotubes for Visible-Light-Driven Water Oxidation

For the sluggish reaction kinetics due to a four-electron transfer process, water oxidation is always a major obstacle to solar splitting of water to hydrogen. It remains a tough challenge to develop efficient nonnoble-metal photocatalysts for water oxidation. Herein, we decorate the host photocatalyst of Bi11VO19 nanotubes with the coatalyst of subnanometer MoOx clusters (denoted as Bi11VO19/MoOx hetero-nanotubes) via a one-step cation-exchange solvothermal reaction using Na2V6O16 nanowires as the hard template. It is observed that the morphology and microstructure of Bi11VO19/MoOx hetero-nanotubes vary with the dosage of Mo source and polyvinylpyrrolidone, as well as with the solvent composition. The optimized Bi11VO19/MoOx hetero-nanotubes significantly enhance the photooxidation of water to oxygen with visible light, delivering an oxygen production rate of 790 μmol g-1 h-1, which is 12 times that of bare Bi11VO19 nanotubes. In situ X-ray photoelectron spectroscopy and (photo)electrochemical characterization suggest that the enhanced photoactivity may be caused by the decorated cocatalyst of MoOx clusters, which extracts electrons from Bi11VO19 nanotubes, leaving an abundance of holes for water photooxidation. This work demonstrates a potential strategy to develop photocatalysts for energy conversion by constructing Bi11VO19-based nanostructures.

Atomic/molecular layer deposition strategies for enhanced CO2 capture, utilisation and storage materials

Elevated levels of carbon dioxide (CO2) in the atmosphere and the diminishing reserves of fossil fuels have raised profound concerns regarding the resulting consequences of global climate change and the future supply of energy. Hence, the reduction and transformation of CO2 not only mitigates environmental pollution but also generates value-added chemicals, providing a dual remedy to address both energy and environmental challenges. Despite notable advancements, the low conversion efficiency of CO2 remains a major obstacle, largely attributed to its inert chemical nature. It is imperative to engineer catalysts/materials that exhibit high conversion efficiency, selectivity, and stability for CO2 transformation. With unparalleled precision at the atomic level, atomic layer deposition (ALD) and molecular layer deposition (MLD) methods utilize various strategies, including ultrathin modification, overcoating, interlayer coating, area-selective deposition, template-assisted deposition, and sacrificial-layer-assisted deposition, to synthesize numerous novel metal-based materials with diverse structures. These materials, functioning as active materials, passive materials or modifiers, have contributed to the enhancement of catalytic activity, selectivity, and stability, effectively addressing the challenges linked to CO2 transformation. Herein, this review focuses on ALD and MLD's role in fabricating materials for electro-, photo-, photoelectro-, and thermal catalytic CO2 reduction, CO2 capture and separation, and electrochemical CO2 sensing. Significant emphasis is dedicated to the ALD and MLD designed materials, their crucial role in enhancing performance, and exploring the relationship between their structures and catalytic activities for CO2 transformation. Finally, this comprehensive review presents the summary, challenges and prospects for ALD and MLD-designed materials for CO2 transformation.

Hollow structured CdS@ZnIn2S4 Z-scheme heterojunction for bifunctional photocatalytic hydrogen evolution and selective benzylamine oxidation

Photocatalytic hydrogen evolution (PHE) is frequently constrained by inadequate light utilization and the rapid combination rate of the photogenerated electron-hole pairs. Additionally, conventional PHE processes are often facilitated by the addition of sacrificial reagents to consume photo-induced holes, which makes this approach economically unfavorable. Herein, we designed a spatially separated bifunctional cocatalyst decorated Z-scheme heterojunction of hollow structured CdS (HCdS) @ZnIn2S4 (ZIS), which was prepared by a sacrificial hard template method followed by photo-deposition. Consequently, PdOx@HCdS@ZIS@Pt exhibited efficient PHE (86.38 mmol·g-1·h-1) and benzylamine (BA) oxidation coupling (164.75 mmol·g-1·h-1) with high selectivity (97.34 %). The unique hollow core-shelled morphology and bifunctional cocatalyst loading in this work hold great potential for the design and synthesis of bifunctional Z-scheme photocatalysts.

Applications of hollow nanostructures in water treatment considering organic, inorganic, and bacterial pollutants

One of the major issues of modern society is water contamination with different organic, inorganic, and contaminants bacteria. Finding cost-effective and efficient materials and methods for water treatment and environment remediation is among the scientists' most important considerations. Hollow-structured nanomaterials, including hollow fiber membranes, hollow spheres, hollow nanoboxes, etc., have shown an exciting capability for wastewater refinement approaches, including membrane technology, adsorption, and photocatalytic procedure due to their extremely high specific surface area, high porosity, unique morphology, and low density. Diverse hollow nanostructures could potentially eliminate organic contaminants, including dyes, antibiotics, oil/water emulsions, pesticides, and other phenolic compounds, inorganic pollutants, such as heavy metal ions, salts, phosphate, bromate, and other ions, and bacteria contaminations. Here, a comprehensive overview of hollow nanostructures' fabrication and modification, water contaminant classification, and recent studies in the water treatment field using hollow-structured nanomaterials with a comparative attitude have been provided, indicating the privilege abd detriments of this class of nanomaterials. Eventually, the future outlook of employing hollow nanomaterials in water refinery systems and the upcoming challenges arising in scaling up are also propounded.

Hollow Nanoreactors for Controlled Photocatalytic Behaviors: Fundamental Theory, Structure-Performance Relationship, and Catalytic Advantages

Hollow nanoreactors (HoNRs) have regarded as an attractive catalytic material for photocatalysis due to their exceptional capabilities in enhancing light harvesting, facilitating charge separation and transfer, and optimizing surface reactions. Developing novel HoNRs offers new options to realize controllable catalytic behavior. However, the catalytic mechanism of photocatalysis occurring in HoNRs has not yet been fully revealed. Against this backdrop, this review elaborates on three aspects: 1) the fundamental theoretical insights of HoNRs-driven photocatalytic kinetics; 2) structure-performance relationship of HoNRs to photocatalysis; 3) catalytic advantages of HoNRs in photocatalytic applications. Specifically, the review focuses on the fundamental theories of HoNRs for photocatalysis and their structural advantages for strengthening light scattering, promoting charge separation and transfer, and facilitating surface reaction kinetics, and the relationship between key structural parameters of HoNRs and their photocatalytic performance is in-depth discussed. Also, future prospects and challenges are proposed. It is anticipated that this review paper will pave the way for forthcoming investigations in the realm of HoNRs for photocatalysis.

Construction of site-specific magnetic Z-scheme CdS/Fe3O4@N-doped graphene aerogel microtube/N-doped TiO2 with porous structure: enhanced catalytic performance in photo-Fenton reaction

The development of composite photocatalysts with high charge transfer efficiency, great visible light absorption, and quick recovery has aroused the interest of many researchers. Herein, based on the hydrothermal assisted vacuum freeze drying method, CdS, Fe3O4, and N-TiO2 were, respectively, fixed in the inner, middle, and outer layers of nitrogen-doped graphene aerogel for preparation of the site-specific magnetic porous Z-scheme CdS/Fe3O4@N-doped graphene aerogel microtube/N-doped TiO2 (CdS/Fe3O4@NGAM/N-TiO2) photocatalyst. For the composite, Fe3O4@NGAM carrier with porous and tubular structure not only helps the recycle and reactants/productions mass transport in the photocatalytic process but also ensures the well-steered transfer of electrons and holes from CdS and N-TiO2 in the Z-type heterojunction system, greatly improving the separation of photogenerated carriers. Besides, Fe3O4 can also work as a Fenton catalyst to activate hydrogen peroxide which is generated in situ by CdS. Thus, the CdS/Fe3O4@NGAM/N-TiO2 composite presents excellent degradation efficiencies towards methyl orange ((MO) 98% removal rate within 50 min), bisphenol A ((BPA) 96% removal rate within 50 min), tetracycline hydrochloride ((TCH) 96% removal rate within 120 min) and strong stabilities after 6 cycles. The free radical removal experiments show that ·O2- and ·OH are the main active substances of catalysis, which further confirms the synergistic effect of photocatalysis and Fenton catalysis.

Distinct Selectivity Control in Solar-Driven Bio-Based α-Hydroxyl Acid Conversion: A Comparison of Pt Nanoparticles and Atomically Dispersed Pt on CdS

Solar-driven photocatalytic lignocellulose conversion is a promising strategy for the sustainable production of high-value chemicals, but selectivity control remains a challenging goal in this field. Here, we report efficient and selective conversion of lignocellulose-derived α-hydroxyl acids to tartaric acid derivatives, α-keto acids, and H2 using Pt-modified CdS catalysts. Pt nanoparticles on CdS selectively produce tartaric acid derivatives via C-C coupling, while atomically dispersed Pt on CdS switches product selectivity to the oxidation reaction to produce α-keto acids. The atomically dispersed Pt species stabilized by Pt-S bonds promote the activation of the hydroxyl group and thus switch product selectivity from tartaric acid derivatives to α-keto acids. A broad range of lignocellulose-derived α-hydroxyl acids was applied for preparing the corresponding tartaric acid derivatives and α-keto acids over the two Pt-modified CdS catalysts. This work highlights the unique performance of metal sulfides in coupling reactions and demonstrates a strategy for rationally tuning product selectivity by engineering the interaction between metal sulfide and cocatalyst.

Biomimetic Photocatalytic System Designed by Spatially Separated Cocatalysts on Z-scheme Heterojunction with Identified Charge-transfer Processes for Boosting Removal of U(VI)

Designing highly efficient photocatalysts with rapid migration of photogenerated charges and surface reaction kinetics for the photocatalytic removal of uranium (U(VI)) from uranium mine wastewater remains a significant challenge. Inspired by natural photosynthesis, a biomimetic photocatalytic system is assembled by designing a novel hollow nanosphere MnO_x @TiO₂ @CdS@Au (MTCA) with loading MnO_x and Au nano particles (Au NPs) cocatalysts on the inner and outer surfaces of the TiO₂ @CdS. The spatially separated cocatalysts efficiently drive the photogenerated charges to migrate in opposite directions, while the Z-scheme heterogeneous shell further separates the interfacial charges. Theoretical calculation identifies multiple consecutive forward charge transfers without charge recombination within MTCA. Thus, MTCA could efficiently remove 99.61% of U(VI) after 15 min of simulated sunlight irradiation within 3 mmol L^-1 NaHCO₃ with 0.231 min^-1 of the reduction rate constant, outperforming most previously reported photocatalysts. MTCA further significantly removes 91.83% of U(VI) from the natural uranium mining wastewater under sunlight irradiation. This study provides a novel approach to designing an ideal biomimetic photocatalyst for remediating environmental pollution.

Hollow Spherical Pd/CdS/NiS with Carrier Spatial Separation for Photocatalytic Hydrogen Generation

Inspired by the unique properties of the three-dimensional hollow nanostructures in the field of photocatalysis, as well as the combination of co-catalyst, porous hollow spherical Pd/CdS/NiS photocatalysts are prepared by stepwise synthesis. The results show that the Schottky junction between Pd and CdS accelerates the transport of photogenerated electrons, while a p-n junction between NiS and CdS traps the photogenerated holes. As co-catalysts, the Pd nanoparticles and the NiS are loaded inside and outside the hollow CdS shell layer, respectively, which combines with the particular characteristic of the hollow structure, resulting in a spatial carrier separation effect. Under the synergy of the dual co-catalyst loading and hollow structure, the Pd/CdS/NiS has favorable stability. Its H₂ production under visible light is significantly increased to 3804.6 μmol/g/h, representing 33.4 times more than that of pure CdS. The apparent quantum efficiency is 0.24% at 420 nm. A feasible bridge for the development of efficient photocatalysts is offered by this work.

Mechanistic Insight into the Synergy between Platinum Single Atom and Cluster Dual Active Sites Boosting Photocatalytic Hydrogen Evolution

In the energy transition context, the design and synthesis of high-performance Pt-based photocatalysts with low Pt content and ultrahigh atom-utilization efficiency for hydrogen production are essential. Herein, a facile approach for decorating atomically dispersed Pt cocatalysts having single-atom (SA) and atomic cluster (C) dual active sites on CdS nanorods (Pt_SA+C /CdS) via atomic layer deposition is reported. The size of the cocatalyst and the spatial intimacy of the cocatalyst active sites are precisely engineered at the atomic scale. The Pt_SA+C /CdS photocatalysts show the optimized photocatalytic hydrogen evolution activity, achieving a reaction rate of 80.4 mmol h^-1 g^-1 , which is 1.6- and 7.3-fold higher than those of the Pt_SA /CdS and Pt_NP /CdS photocatalysts, respectively. Thorough characterization and theoretical calculations reveal that the enhanced photocatalytic activity is due to a remarkable synergy between SAs and atomic clusters as dual active sites, which are responsible for water adsorption-dissociation and hydrogen desorption, respectively. A similar synergetic effect is found in a representative Pt/TiO₂ system, indicating the generality of the strategy. This study demonstrates the significance of the synergy between active sites for enhancing the reaction efficiency, opening a new avenue for the rational design of atomically dispersed photocatalysts with high efficiency.

An overview of wastewater treatment using combined heterogeneous photocatalysis and membrane distillation

The need for efficient remediation solutions to wastewater has risen due to the concerning prevalence of toxic organic pollutants. It is possible for the linked photocatalysis-membrane separation system to concurrently achieve the photoreaction of pollutants and their removal from wastewater in order to accomplish the goal of completely purifying the wastewater. This investigation's objective is to provide analytical overview of the photocatalytic and membrane coupling process, photocatalytic membrane reactors, and the potential applications of these technologies in the treatment of wastewater for the persistent organic matter removal. In the review, an examination of photocatalytic and membrane processes to remove organic compounds from wastewater is presented. Based on the literature analysis, it was observed that the application of photocatalytic membrane reactors is significantly influenced by a wide variety of factors. Some of these factors include pollutant concentration, dissolved oxygen, aeration, pH, and hydraulic retention time. Light intensity is another factor that has a significant influence. It was also revealed how distillation membranes work when integrated with photocatalytic process. This brief overview will help researchers understand how successful coupled photocatalytic and membrane distillation are in the treatment of wastewater containing organic pollutants.

An NIR-Driven Upconversion/C3N4/CoP Photocatalyst for Efficient Hydrogen Production by Inhibiting Electron-Hole Pair Recombination for Alzheimer's Disease Therapy

Redox imbalance and abnormal amyloid protein (Aβ) buildup are key factors in the etiology of Alzheimer's disease (AD). As an antioxidant, the hydrogen molecule (H₂) has the potential to cure AD by specifically scavenging highly harmful reactive oxygen species (ROS) such as ^•OH. However, due to the low solubility of H₂ (1.6 ppm), the traditional H₂ administration pathway cannot easily achieve long-term and effective accumulation of H₂ in the foci. Therefore, how to achieve the continuous release of H₂ in situ is the key to improve the therapeutic effect on AD. As a corollary, we designed a rare earth ion doped g-C₃N₄ upconversion photocatalyst, which can respond to NIR and realize the continuous production of H₂ by photocatalytic decomposition of H₂O in biological tissue, which avoids the problem of the poor penetration of visible light. The introduction of CoP cocatalyst accelerates the separation and transfer of photogenerated electrons in g-C₃N₄, thus improving the photocatalytic activity of hydrogen evolution reaction. The morphology of the composite photocatalyst was shown by transmission electron microscopy, and the crystal structure was studied by X-ray diffractometry and Raman analysis. In addition, the ability of g-C₃N₄ to chelate metal ions and the photothermal properties of CoP can inhibit Aβ and reduce the deposition of Aβ in the brain. Efficient in situ hydrogen production therapy combined with multitarget synergism solves the problem of a poor therapeutic effect of a single target. In vivo studies have shown that UCNP@CoP@g-C₃N₄ can reduce Aβ deposition, improve memory impairment, and reduce neuroinflammation in AD mice.

Spatial Separation of Cocatalysts on Z-Scheme Organic/Inorganic Heterostructure Hollow Spheres for Enhanced Photocatalytic H2 Evolution and In-Depth Analysis of the Charge-Transfer Mechanism

A Z-scheme heterojunction with spatially separated cocatalysts is proposed for overcoming fundamental issues in photocatalytic water splitting, such as inefficient light absorption, charge recombination, and sluggish reaction kinetics. For efficient light absorption and interfacial charge separation, Z-scheme organic/inorganic heterojunction photocatalysts are synthesized by firmly immobilizing ultrathin g-C₃ N₄ on the surface of TiO₂ hollow spheres via electrostatic interactions. Additionally, two cocatalysts, Pt and IrO_x , are spatially separated along the Z-scheme charge-transfer pathway to enhance surface charge separation and reaction kinetics. The as-prepared Pt/g-C₃ N₄ /TiO₂ /IrO_x (PCTI) hollow sphere photocatalyst exhibits an exceptional H₂ evolution rate of 8.15 mmol h^-1 g^-1 and a remarkable apparent quantum yield of 24.3% at 330 nm in the presence of 0.5 wt% Pt and 1.2 wt% IrO_x cocatalysts on g-C₃ N₄ and TiO₂ , respectively. Photoassisted Kelvin probe force microscopy is used to systematically analyze the Z-scheme charge-transfer mechanism within PCTI. Furthermore, the benefits of spatially separating cocatalysts in the PCTI system are methodically investigated in comparison to randomly depositing them. This work adequately demonstrates that the combination of a Z-scheme heterojunction and spatially separated cocatalysts can be a promising strategy for designing high-performance photocatalytic platforms for solar fuel production.

Charge Separation between Pt Co-catalysts and Plasmonic Au in Pt-Au/C3N4 Photocatalysts

Chemical processes induced by surface plasmon resonance have received great attention due to the wide spectral absorption and tunable optical property. Co-catalysts have been introduced into plasmonic-metal/semiconductor photocatalysts to inhibit the recombination of plasmon-induced carriers. However, it is unclear how the locations of co-catalysts (on the surface of plasmonic metal or the semiconductor) affect the plasmonic photocatalystic reactions. Herein, we report that Pt co-catalysts can be selectively deposited on Au nanoparticles (NPs) of Au/C₃N₄ photocatalysts through an atomic layer deposition method. Compared with the Pt co-catalysts exclusively on C₃N₄, Pt solely on Au NPs has a 4.5-fold increase in activity for plasmonic hydrogen evolution. The reduced photoluminescence intensity and prolonged photoluminescence lifetime reveal that Pt solely on Au NPs provides higher charge separation efficiency. The enhanced photocatalytic activity of Pt co-catalysts solely on Au NPs is attributable to the more efficient and direct utilization of the plasmon resonance-induced electrons and separation of electrons and holes.

Plasmonic enhanced photocatalytic activity of Ag/TiO2 tube-in-tube fibers

Ag nanoparticle was found to significantly enhance the photocatalytic activity of self-organized TiO₂ nanotube structures. Herein, novel Ag/TiO₂ tube-in-tube fibers have been prepared by a facile electrospinning technology and calcination process. Employed as the photocatalyst, the composite could efficiently catalyze the photodegradation of the model organic pollutant, rhodamine B under visible light irradiation, exhibiting a superior photocatalytic activity than the undoped TiO₂ tube-in-tube fibers. This enhanced activity has been ascribed to plasmonic characteristics of Ag nanoparticles, which promote the light absorption and charge transfer feasibility. The simple, low-cost and green fabrication route of the composite provides a novel means for preparing similar materials, holding great promise for wider application in the future.

Multiple cobalt active sites evenly embedded in mesoporous carbon nanospheres derived from a polymer-metal-organic framework: efficient removal and photodegradation of malachite green

A series of robust photocatalysts of mesoporous carbon nanospheres embedded with multiple cobalt active sites (Co/Co x O y @mC) have been constructed for efficient removal and photodegradation of malachite green (MG). Here, a cobalt-based polymeric-metal-organic framework (polyMOF(Co)) was constructed by using a polyether ligand containing 1,4-benzenedicarboxylic acid units. Afterward, polyMOF(Co) was calcined into a series of Co/Co x O y @mC hybrids at diverse high temperatures (400, 600, and 800 °C) under a N2 atmosphere. Therefore, Co coordination centers were transformed into various active sites such as Co, CoO, and Co3O4, which were embedded within the mesoporous carbon network derived from the polymeric skeleton. Considering the even distribution of Co-related active species and high porosity inherited from polyMOF(Co), the constructed Co/Co x O y @mC hybrid obtained at 600 °C illustrated higher removal ability (79%) with a maximum adsorption capacity of 314 mg g-1 within 120 min and better photodegradation performance (degradation rate of 95%) toward MG than those of the other photocatalysts obtained at 400 and 800 °C. Moreover, the possible photocatalytic reaction mechanisms, including the transfer behavior of charge carriers, generation of reactive species, and intermediate degradation of products, were provided. The present work showed an alternative strategy for the feasible and efficient preparation of photocatalysts based on MOFs.

Research on the Influence of the Interfacial Properties Between a Cu3 BiS3 Film and an Inx Cd1- x S Buffer Layer for Photoelectrochemical Water Splitting

The ternary compound photovoltaic semiconductor Cu3 BiS3 thin film-based photoelectrode demonstrates a quite promising potential for photoelectrochemical hydrogen evolution. The presented high onset potential of 0.9 VRHE attracts much attention and shows that the Cu3 BiS3 thin films are quite good as an efficient solar water splitting photoelectrode. However, the CdS buffer does not fit the Cu3 BiS3 thin film: the conduction band offset between CdS and Cu3 BiS3 reaches 0.7 eV, and such a high conduction band offset (CBO) significantly increases the interfacial recombination ratio and is the main reason for the relatively low photocurrent of the Cu3 BiS3 /CdS photoelectrode. In this study, the Inx Cd1- x S buffer layer is found to be significantly lowered the CBO of CBS/buffer and that the In incorporation ratio of the buffer influences the CBO value of the CBS/buffer. The Pt-TiO2 /In0.6 Cd0.4 S/Cu3 BiS3 photocathode exhibits an appreciable photocurrent density of ≈12.20 mA cm-2 at 0 VRHE with onset potential of more than 0.9 VRHE , and the ABPE of the Cu3 BiS3 -based photocathode reaches the highest value of 3.13%. By application of the In0.6 Cd0.4 S buffer, the Cu3 BiS3 -BiVO4 tandem cell presents a stable and excellent unbiased STH of 2.57% for over 100 h.

PtBi-β-CD-Ce6 Nanozyme for Combined Trimodal Imaging-Guided Photodynamic Therapy and NIR-II Responsive Photothermal Therapy

Combined photothermal/photodynamic therapy is a promising strategy to achieve an enhanced anticancer effect. However, hypoxia is one of the representative characteristics of the microenvironment of solid tumors, which not only attenuates the therapeutic effects but also promotes tumor invasion and metastasis. Herein, a PtBi-β-CD-Ce6 nanoplatform for the generation of sustained O2 was constructed for more effective tumor therapy. In detail, the catalase (CAT)-like nanozyme, PtBi, which could decompose H2O2 to produce O2, was modified with β-cyclodextrin (β-CD). O2 would be converted into 1O2 by PtBi-β-CD-Ce6 for enhanced photodynamic therapy (PDT) under 650 nm laser irradiation. In addition, by reason of excellent absorption in the near-infrared-II (NIR-II) region, PtBi-β-CD-Ce6 was used for photoacoustic imaging (PA) and photothermal imaging (PT)-guided photothermal therapy (PTT) in the NIR-II biowindow. Furthermore, PtBi-β-CD-Ce6 could be elected to serve as a contrast agent for X-ray computed tomography (CT) imaging due to the apparent X-ray attenuation capability of the Pt and Bi elements themselves. Therefore, by integrating the advantages of overcoming the hypoxia function and photothermal effect into a single nanoplatform, PtBi-β-CD-Ce6 showed an immense possibility in multimodal imaging-guided combined PDT/PTT.

Designing Sites in Heterogeneous Catalysis: Are We Reaching Selectivities Competitive With Those of Homogeneous Catalysts?

A critical review of different prominent nanotechnologies adapted to catalysis is provided, with focus on how they contribute to the improvement of selectivity in heterogeneous catalysis. Ways to modify catalytic sites range from the use of the reversible or irreversible adsorption of molecular modifiers to the immobilization or tethering of homogeneous catalysts and the development of well-defined catalytic sites on solid surfaces. The latter covers methods for the dispersion of single-atom sites within solid supports as well as the use of complex nanostructures, and it includes the post-modification of materials via processes such as silylation and atomic layer deposition. All these methodologies exhibit both advantages and limitations, but all offer new avenues for the design of catalysts for specific applications. Because of the high cost of most nanotechnologies and the fact that the resulting materials may exhibit limited thermal or chemical stability, they may be best aimed at improving the selective synthesis of high value-added chemicals, to be incorporated in organic synthesis schemes, but other applications are being explored as well to address problems in energy production, for instance, and to design greener chemical processes. The details of each of these approaches are discussed, and representative examples are provided. We conclude with some general remarks on the future of this field.

Synthesis and application of CdS nanorods for LED-based photocatalytic degradation of tetracycline antibiotic

With the rapid development of pharmaceutical industrialization, increased consumption of drugs and discharged sewage contains antibiotics that lead to water contamination. For this purpose, removal of antibiotics from aquatic environment is emphasizing the need to produce clean water using easy separable catalysts through photocatalytic water remediation and thus the semiconductor photocatalysts have presently gained fascinating unprecedented research attention. Herein, we present the synthesis of semiconductor CdS nanorods by a facile hydrothermal procedure using ethylene diamine as a coordinating agent. Then, we subsequently studied the photocatalytic activity of CdS nanorods under blue and white LED light irradiation for the degradation of tetracycline antibiotic as a model compound. The light dependent photocatalytic activity of CdS nanorods demonstrated that CdS nanorods possess higher catalytic efficiency in presence of blue light compared to white light toward the photocatalytic degradation of tetracycline antibiotic. We have also studied the photocatalytic activity in presence of various light intensity. These CdS nanorods exhibited the highest tetracycline degradation efficacy of 95.6% within 60 min in presence of blue light (intensity: 200W/m²) without any supplementary oxygen sources during the degradation reaction. The photocatalytic mechanism of the tetracycline degradation has been elucidated by scavenging experiment. The experimental results indicate the formation of reactive oxygen species during photocatalytic degradation of tetracycline antibiotic. This work represents an alternative route to develop heterogeneous photocatalyst for antibiotics degradation due to the outstanding efficiency and stability of the CdS nanorods as well as easy separation through simple filtration method. It is anticipated that this work will shed light in the practical applications of CdS nanorods for environmental remediation through wastewater treatment.

Development and Functionalization of Visible-Light-Driven Water-Splitting Photocatalysts

With global warming and the depletion of fossil resources, our fossil fuel-dependent society is expected to shift to one that instead uses hydrogen (H2) as a clean and renewable energy. To realize this, the photocatalytic water-splitting reaction, which produces H2 from water and solar energy through photocatalysis, has attracted much attention. However, for practical use, the functionality of water-splitting photocatalysts must be further improved to efficiently absorb visible (Vis) light, which accounts for the majority of sunlight. Considering the mechanism of water-splitting photocatalysis, researchers in the various fields must be employed in this type of study to achieve this. However, for researchers in fields other than catalytic chemistry, ceramic (semiconductor) materials chemistry, and electrochemistry to participate in this field, new reviews that summarize previous reports on water-splitting photocatalysis seem to be needed. Therefore, in this review, we summarize recent studies on the development and functionalization of Vis-light-driven water-splitting photocatalysts. Through this summary, we aim to share current technology and future challenges with readers in the various fields and help expedite the practical application of Vis-light-driven water-splitting photocatalysts.

Promotion of the Co3O4/TiO2 Interface on Catalytic Decomposition of Ammonium Perchlorate

Supports can widely affect or even dominate the catalytic activity and selectivity of nanoparticles because atomic geometry and electronic structures of active sites can be regulated, especially at the interface of nanoparticles and supports. However, the underlying mechanisms of most systems are still not fully understood yet. Herein, we construct the interface of Co₃O₄/TiO₂ to boost ammonium perchlorate (AP) catalytic decomposition. This catalyst shows enhanced catalytic performance. With the addition of 2 wt % Co₃O₄/TiO₂ catalysts, AP decomposition peak temperature decreases from 435.7 to 295.0 °C and activation energy decreases from 211.5 to 137.7 kJ mol^-1. By combining experimental and theoretical studies, we find that Co₃O₄ nanoparticles can be strongly anchored onto TiO₂ supports accompanied by charge transfer. Moreover, at the interfaces in the Co₃O₄/TiO₂ nanostructure, NH₃ adsorption can be enhanced through hydrogen bonds. Our research studies provide new insights into the promotion effects of the nanoparticle/support system on the AP decomposition process and inspire the design of efficient catalysts.

Hydrogen production technologies - Membrane based separation, storage and challenges

The production of hydrogen, its separation, and storage for use as a primary source of energy is an important component of the green energy economy of the world. Hydrogen is a potential non-carbon-based energy source, which is gradually replacing the dependency on fossil fuels. It is anticipated that as the alternative fuel since hydrogen can be produced from green and clean sources. The evolution of hydrogen from renewable and non-renewable sources by various technologies has now gained tremendous research and industrial interest. The most appropriate methods for hydrogen generation involve the direct conversion of solar energy, exploitation of solar and wind energy for the electrolysis of water, besides conversion of fuel and biomass. To produce cleaner hydrogen and its separation from the chemical impurities is crucial and several methods including photobiological, photoelectrochemical, electrochemical, photocatalytic, thermochemical, thermolysis, and steam gasification have been used. The diverse types of membranes along with the pressure gas swing adsorption technique is another technique used to separate hydrogen, but the storage of hydrogen in an inexpensive, safe, compact, and environmentally friendly manner is one of the major concerns contributing to the country's economy. Apart from the countless advantages, storage and handling of hydrogen is a serious concern. Owing to its high inflammability, enough safety measures should be adopted during its production and storage as a fuel. It is necessary to provide information regarding the production technologies, storage, and separation methods of hydrogen and the present review addresses these issues.

Advanced catalytic CO2 hydrogenation on Ni/ZrO2 with light induced oxygen vacancy formation in photothermal conditions at medium-low temperatures

Selective CH4 formation from CO2 hydrogenation is an appealing yet challenging sunlight-driven or thermal-driven process due to low solar energy utilization efficiency or high energy input.

CdS/MnS p-n heterojunction with directional carriers diffusion path for efficient photocatalytic H2 production

Photocatalytic reactions usually involve the reduction of photogenerated electrons and the oxidation of photogenerated holes. The migration process of photongenerated holes is slower than photogenerated electronics, and the oxidation potential...

Photodeposition of CoOx nanoparticles on BiFeO3 nanodisk for efficiently piezocatalytic degradation of rhodamine B by utilizing ultrasonic vibration energy

Piezoelectric materials have received much attention due to their great potential in environmental remediation by utilizing vibrational energy. In this paper, a novel piezoelectric catalyst, CoOx nanoparticles anchored BiFeO3 nanodisk composite, was intentionally synthesized via a photodeposition method and applied in piezocatalytic degradation of rhodamine B (RhB) under ultrasonic vibration. The as-synthesized CoOx/BiFeO3 composite presents high piezocatalytic efficiency and stability. The RhB degradation rate is determined to be 1.29 h-1, which is 2.38 folds higher than that of pure BiFeO3. Via optimizing the reaction conditions, the piezocatalytic degradation rate of the CoOx/BiFeO3 can be further increased to 3.20 h-1. A thorough characterization was implemented to investigate the structure, piezoelectric property, and charge separation efficiency of the CoOx/BiFeO3 to reveal the nature behind the high piezocatalytic activity. It is found that the CoOx nanoparticles are tightly adhered and uniformly dispersed on the surface of the BiFeO3 nanodisks. Strong interaction between CoOx and BiFeO3 triggers the formation of a heterojunction structure, which further induces the migration of the piezoinduced holes on the BiFeO3 to CoOx nanoparticles. The recombination of electron-hole pairs is retarded, thereby increasing the piezocatalytic performance greatly. This work may offer a new paradigm for the design of high-efficiency piezoelectric catalysts.

Porous Ga2 O3 Nanotubes Derived from Urease-Mediated Interfacially-Grown NH4 Ga(OH)2 CO3 for High-Efficient Hydrogen Evolution

The authors proposed a novel template-free strategy, urease-mediated interfacial growth of NH₄ Ga(OH)₂ CO₃ nanotubes at 20-50 °C, to fabricate the porous Ga₂ O₃ nanotubes. The subtlety of the proposed strategy is all the products from urea enzymolysis are utilized in formation of NH₄ Ga(OH)₂ CO₃ precipitates, and the key for interfacial growth of NH₄ Ga(OH)₂ CO₃ nanotubes is the dynamic match between the rate of CO₂ bubble fusion and NH₄ Ga(OH)₂ CO₃ precipitation. The proposed strategy works well for the doped porous Ga₂ O₃ nanotubes. As a proof-of-concept, the porous β-Ga₂ O₃ and β-Ga₂ O₃ :Cr_0.001 nanotubes are used as photocatalysts or co-catalysts with Pt, for H₂ evolution from water splitting. The H₂ evolution rate of porous β-Ga₂ O₃ nanotubes reach 39.3 mmol g^-1 h^-1 with solar-to-hydrogen (STH) conversion efficiency of 2.11% (Hg lamp) or 498 µmol g^-1 h^-1 with STH of 0.03% (Xe lamp) respectively, both about 3 times of β-Ga₂ O₃ nanoparticles synthesized at pH 9.0 without urease. The Cr-doping enhances the in-the-dark H₂ evolution rate pre-lighted by Hg lamp, and Pt co-catalysis further elevates the H₂ evolution rate, for instance, the H₂ evolution rate of Pt-loaded β-Ga₂ O₃ :Cr_0.001 nanotubes reaches 54.7 mmol g^-1 h^-1 with STH of 2.94% under continuous lighting of Hg lamp and 1062 µmol g^-1 h^-1 in-the-dark.

Rhodium nanoparticles confined in titania nanotubes for efficient Hydrogen evolution from Ammonia Borane

Designing efficient catalysts for hydrogen evolution from hydrolysis of ammonia borane (AB) have attracted considerable attention. Rhodium (Rh) based catalysts with rational design present remarkable catalytic performance for the reaction. Herein, we report the confined Rh@TiO₂ catalysts synthesized by atomic layer deposition combining with the sacrificial template approach, in which the Rh nanoparticles are uniformly confined on the inner surface of the porous titania nanotubes. The optimized catalysts show high catalytic activity with a turnover frequency value of 334.1 mol_H2·mol_Rh^-1·min^-1 and better durability. Mechanistic investigation demonstrates that the cleavage of OH bands in water should be the rate determining step, and the appropriate concentration of NaOH can further enhance the hydrogen evolution activity. The catalysts can also achieve the hydrogenation of various organic substrates using AB as the hydrogen source. In addition, our present strategy is general and can be extended to the synthesis of other confined catalysts for various catalytic reactions.

Enhancing Photocatalytic Hydrogen Production via the Construction of Robust Multivariate Ti-MOF/COF Composite

Titanium metal-organic frameworks (Ti-MOFs), as an appealing type of artificial photocatalysts, have shown great potentials in the field of solar energy conversion due to their well-studied photo-redox activity similar to TiO 2 and good optical responsiveness of linkers serving as the antenna to absorb visible-light. Although enormous efforts have been dedicated to developing Ti-MOFs with high photocatalytic activity, their solar energy conversion performances are still poor. Herein, a covalent-integrated strategy has been implemented to construct a series of multivariate Ti-MOF/COF hybrid materials, PdTCPP⸦PCN-415(NH 2 )/TpPa (composites 1, 2, and 3), featuring excellent visible-light utilization, suitable band gap, and high surface area for photocatalytic H 2 production. Notably, the resulting composites demonstrated remarkably enhanced visible-light-driven photocatalytic H 2 evolution performance, especially for the composite 2 with the maximum H 2 evolution rate of 13.98 mmol g -1 h -1 (turn-over frequency (TOF) = 227 h -1 ), which is much higher than the prototypical counterparts, PdTCPP⸦PCN-415(NH 2 ) (0.21 mmol g -1 h -1 ) and TpPa (6.51 mmol g -1 h -1 ). Our work thereby suggests a new approach to develop highly efficient photocatalysts for photocatalytic H 2 evolution reaction and beyond.

pH-induced hydrothermal synthesis of Bi2WO6 nanoplates with controlled crystal facets for switching bifunctional photocatalytic water oxidation/reduction activity

Bifunctional photocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have attracted growing interest to understand the mechanisms governing different evolution reactions, and the bifunctional activity of a single type of crystalline photocatalyst has gained especial attention. We herein report the high photocatalytic OER and HER activities of Bi₂WO₆ nanoplates (BWO NPs) which are synthesized by a simple hydrothermal method, and the switchable OER and HER performances controlled by the pH value of the precursor solvent. In the pH range from 4 to 9, the thickness of BWO NPs along the [001] direction exhibits interesting dependence on the pH value, which decreases as the pH value increases. Correspondingly, the BWO NPs obtained at the pH value of 7 (BWO-7) show the highest photocatalytic OER activity, while the BWO NPs synthesized at the pH value of 9 (BWO-9) exhibit the highest photoactivity towards HER. The electronic band structure analysis indicates that the highest photocatalytic OER activity is related to the band alignment of the valence band maximum of Bi₂WO₆, which determines the efficient separation of photogenerated electrons and holes as well as the fast charge transfer kinetics. The crystal facet evolution resulting from thickness reduction promotes the exposure of {001} facets for HER and decreases the exposure of {100} and {010} facets for OER. This work provides new insights into the combined effects of crystal facets and electronic band structures on photocatalysis.

Morphology Engineering of BiVO4 with CoOx Derived from Cobalt-containing Polyoxometalate as Co-catalyst for Oxygen Evolution

Bismuth vanadate (BiVO₄ ) as a metal oxidation semiconductor has stimulated extensive attention in the photocatalytic water splitting field. However, the poor transport ability and easy recombination of charge carriers limit photocatalytic water oxidation activity of pure BiVO₄ . Herein, the photocatalytic activity of BiVO₄ is enhanced via adjusting its morphology and combination co-catalyst. First, the Cu-BiVO₄ was synthesized by copper doping to control the growth of {110} facet of BiVO₄ , which is regarded for the separation of photo-generated charge carriers. Then the CoO_x in-situ generated from K₆ [SiCo^II (H₂ O)W₁₁ O₃₉ ] ⋅ 16H₂ O was photo-deposited on Cu-BiVO₄ surface as co-catalyst to speed up reaction kinetics. Cu-BiVO₄ @CoO_x hybrid catalyst shows highest photocatalytic activity and best stability among all the prepared catalysts. Oxygen evolution is about 34.6 μmol in pH 4 acetic acid buffer under 420 nm LED irradiation, which is nearly 20 times higher than that of pure BiVO₄ . Apparent quantum efficiency (AQE) in 1 h and O₂ yield are 1.83% and 23.1%, respectively. O₂ evolution amount nearly maintains the original value even after 5 cycles.

Porous Inorganic Materials for Bioanalysis and Diagnostic Applications

Porous inorganic materials play an important role in adsorbing targeted analytes and supporting efficient reactions in analytical science. The detection performance relies on the structural properties of porous materials, considering the tunable pore size, shape, connectivity, etc. Herein, we first clarify the enhancement mechanisms of porous materials for bioanalysis, concerning the detection sensitivity and selectivity. The diagnostic applications of porous material-assisted platforms by coupling with various analytical techniques, including electrochemical sensing, optical spectrometry, and mass spectrometry, etc., are then reviewed. We foresee that advanced porous materials will bring far-reaching implications in bioanalysis toward real-case applications, especially as diagnostic assays in clinical settings.

A Robust Narrow Bandgap Vanadium Tetrasulfide Sonosensitizer Optimized by Charge Separation Engineering for Enhanced Sonodynamic Cancer Therapy

The development and optimization of sonosensitizers for elevating intratumoral reactive oxygen species (ROS) are definitely appealing in current sonodynamic therapy (SDT). Given this, branched vanadium tetrasulfide (VS₄ ) nanodendrites with a narrower bandgap (compared with the most extensively explored sonosensitizers) are presented as a new source of sonosensitizer, which allows a more effortless separation of sono-triggered electron-hole pairs for ROS generation. Specifically, platinum (Pt) nanoparticles and endogenous high levels of glutathione (GSH) are rationally engineered to further optimize its sono-sensitized performance. As cocatalyst, Pt is conducive to trapping electrons, whereas GSH, as a natural hole-scavenger, tends to capture holes. Compared with the pristine VS₄ sonosensitizer, the GSH-Pt-VS₄ nanocomposite can greatly prolong the lifetime of the charge and confer a highly efficacious ROS production activity. Furthermore, such nanoplatforms are capable of reshaping tumor microenvironments to realize ROS overproduction, contributed by overcoming tumor hypoxia to improve SDT-triggered singlet oxygen production, catalyzing endogenic hydrogen peroxide into destructive hydroxyl radicals for chemodynamic therapy, and depleting GSH to amplify intratumoral oxidative stress. All these combined effects result in a significantly efficient tumor suppression outcome. This study enriches sonosensitizer research and proves that sonosensitizers can be rationally optimized by charge separation engineering strategy.

Dual metal nanoparticles within multicompartmentalized mesoporous organosilicas for efficient sequential hydrogenation

Controlling localization of multiple metal nanoparticles on a single support is at the cutting edge of designing cascade catalysts, but is still a scientific and technological challenge because of the lack of nanostructured materials that can not only host metal nanoparticles in different sub-compartments but also enable efficient molecular transport between different metals. Herein we report a multicompartmentalized mesoporous organosilica with spatially separated sub-compartments that are connected by short nanochannels. Such a unique structure allows co-localization of Ru and Pd nanoparticles in a nanoscale proximal fashion. The so designed cascade catalyst exhibits an order of magnitude activity enhancement in the sequential hydrogenation of nitroarenes to cyclohexylamines compared with its mono/bi-metallic counterparts. Crucially, an interesting phenomenon of neighboring metal-assisted hydrogenation via hydrogen spillover is observed, contributing to the significant enhancement in catalytic efficiency. The multicompartmentalized architectures along with the revealed mechanism of accelerated hydrogenation provide vast opportunity for designing efficient cascade catalysts.

Oxygen-Based Nanocarriers to Modulate Tumor Hypoxia for Ameliorated Anti-Tumor Therapy: Fabrications, Properties, and Future Directions

Over the past five years, oxygen-based nanocarriers (NCs) to boost anti-tumor therapy attracted tremendous attention from basic research and clinical practice. Indeed, tumor hypoxia, caused by elevated proliferative activity and dysfunctional vasculature, is directly responsible for the less effectiveness or ineffective of many conventional therapeutic modalities. Undeniably, oxygen-generating NCs and oxygen-carrying NCs can increase oxygen concentration in the hypoxic area of tumors and have also been shown to have the ability to decrease the expression of drug efflux pumps (e.g., P-gp); to increase uptake by tumor cells; to facilitate the generation of cytotoxic reactive oxide species (ROS); and to evoke systematic anti-tumor immune responses. However, there are still many challenges and limitations that need to be further improved. In this review, we first discussed the mechanisms of tumor hypoxia and how it severely restricts the therapeutic efficacy of clinical treatments. Then an up-to-date account of recent progress in the fabrications of oxygen-generating NCs and oxygen-carrying NCs are systematically introduced. The improved physicochemical and surface properties of hypoxia alleviating NCs for increasing the targeting ability to hypoxic cells are also elaborated with special attention to the latest nano-technologies. Finally, the future directions of these NCs, especially towards clinical translation, are proposed. Therefore, we expect to provide some valued enlightenments and proposals in engineering more effective oxygen-based NCs in this promising field in this comprehensive overview.

One-Dimensional (1D) Nanostructured Materials for Energy Applications

At present, the world is at the peak of production of traditional fossil fuels. Much of the resources that humanity has been consuming (oil, coal, and natural gas) are coming to an end. The human being faces a future that must necessarily go through a paradigm shift, which includes a progressive movement towards increasingly less polluting and energetically viable resources. In this sense, nanotechnology has a transcendental role in this change. For decades, new materials capable of being used in energy processes have been synthesized, which undoubtedly will be the cornerstone of the future development of the planet. In this review, we report on the current progress in the synthesis and use of one-dimensional (1D) nanostructured materials (specifically nanowires, nanofibers, nanotubes, and nanorods), with compositions based on oxides, nitrides, or metals, for applications related to energy. Due to its extraordinary surface-volume relationship, tunable thermal and transport properties, and its high surface area, these 1D nanostructures have become fundamental elements for the development of energy processes. The most relevant 1D nanomaterials, their different synthesis procedures, and useful methods for assembling 1D nanostructures in functional devices will be presented. Applications in relevant topics such as optoelectronic and photochemical devices, hydrogen production, or energy storage, among others, will be discussed. The present review concludes with a forecast on the directions towards which future research could be directed on this class of nanostructured materials.

Co and Pt Dual-Single-Atoms with Oxygen-Coordinated Co-O-Pt Dimer Sites for Ultrahigh Photocatalytic Hydrogen Evolution Efficiency

The platinum single-atom-catalyst is verified as a very successful route to approach the size limit of Pt catalysts, while how to further improve the catalytic efficiency of Pt is a fundamental scientific question and is challenging because the size issue of Pt is approached at the ultimate ceiling as single atoms. Here, a new route for further improving Pt catalytic efficiency by cobalt (Co) and Pt dual-single-atoms on titanium dioxide (TiO₂ ) surfaces, which contains a fraction of nonbonding oxygen-coordinated Co-O-Pt dimers, is reported. These Co-Pt dimer sites originate from loading high-density Pt single-atoms and Co single-atoms, with them anchoring randomly on the TiO₂ substrate. This dual-single-atom catalyst yields 13.4% dimer sites and exhibits an ultrahigh and stable photocatalytic activity with a rate of 43.467 mmol g^-1 h^-1 and external quantum efficiency of ≈83.4% at 365 nm. This activity far exceeds those of equal amounts of Pt single-atom and typical Pt clustered catalysts by 1.92 and 1.64 times, respectively. The enhancement mechanism relies on the oxygen-coordinated Co-O-Pt dimer coupling, which can mutually optimize the electronic states of both Pt and Co sites to weaken H* binding. Namely, the "mute" Co single-atom is activated by Pt single-atom and the activity of the Pt atom is further enhanced through the dimer interaction. This strategy of nonbonding interactive dimer sites and the oxygen-mediated catalytic mechanisms provide emerging rich opportunities for greatly improving the catalytic efficiency and developing novel catalysts with creating new electronic states.

Spatially Separating Redox Centers and Photothermal Effect Synergistically Boosting the Photocatalytic Hydrogen Evolution of ZnIn2 S4 Nanosheets

Spatially separated loading of reductive and oxidative cocatalysts is a useful strategy for expediting charge separation and surface reaction kinetics, which are two key factors for determining the photocatalytic efficiency. However, loading the spatial separation of dual cocatalysts on a 2D photocatalyst is still a great challenge. Herein, decorating the spatial separation of oxidative and reductive cocatalysts on ZnIn₂ S₄ nanosheets is realized by designing a ternary Co₉ S₈ @ZnIn₂ S₄ @PdS (CS@ZIS@PS) hollow tubular core-shell structure. Particularly, Co₉ S₈ and PdS functionally serve as the reduction and oxidation cocatalysts, respectively. Experimental results confirm that the spatial separation of Co₉ S₈ and PdS cocatalysts not only efficiently improve charge separation and accelerate surface reduction-oxidation kinetics, but also generate a photothermal effect to further enhance charge transfer and surface reaction kinetics. As a result, the optimized CS@ZIS@PS yields a remarkable H₂ evolution rate of 11407 µmol g^-1 h^-1 , and the apparent quantum efficiency reaches 71.2% at 420 nm, which is one of the highest values among ZnIn₂ S₄ so far. The synergistic effect of spatially separated dual cocatalysts and photothermal effect may be applied to other 2D materials for efficient solar energy conversion.

Yolk-shell nanostructures: synthesis, photocatalysis and interfacial charge dynamics

Solar energy has long been regarded as a promising alternative and sustainable energy source. In this regard, photocatalysts emerge as a versatile paradigm that can practically transform solar energy into chemical energy. At present, unsatisfactory conversion efficiency is a major obstacle to the widespread deployment of photocatalysis technology. Many structural engineering strategies have been proposed to address the issue of insufficient activity for semiconductor photocatalysts. Among them, creation of yolk-shell nanostructures which possess many beneficial features, such as large surface area, efficient light harvesting, homogeneous catalytic environment and enhanced molecular diffusion kinetics, has attracted particular attention. This review summarizes the developments that have been made for the preparation and photocatalytic applications of yolk-shell nanostructures. Additional focus is placed on the realization of interfacial charge dynamics and the possibility of achieving spatial separation of charge carriers for this unique nanoarchitecture as charge transfer is the most critical factor determining the overall photocatalytic efficiency. A future perspective that can facilitate the advancement of using yolk-shell nanostructures in sophisticated photocatalytic systems is also presented.