Construction of Infrared-Light-Responsive Photoinduced Carriers Driver for Enhanced Photocatalytic Hydrogen Evolution

ZnFe2O4@WO3-X /Polypyrrole: An Efficient Ternary Photocatalytic System for Energy and Environmental Application

Environmental protection and the necessity of green energy have become fundamental concerns for humankind. However, rapid recombination of photoexcitons in semiconductors often gets in the path of photocatalytic reactions and annoyingly suppresses the photocatalytic activity. In this study, a polypyrrole (PPY)-supported step-scheme (S-scheme) ZnFe₂O₄@WO_3-X (PZFW15) ternary composite was fabricated by a multistep process: hydrothermal and calcination processes, followed by polymerization. During the formation of the heterojunction, the oxygen vacancy (OV) on WO_3-X promotes effective separation and increases the redox power of the photogenerated excitons via the built-in internal electric field of S-scheme pathways between ZnF and WO_3-X. The successful construction of the S-scheme heterojunction was substantiated through X-ray photoelectron spectroscopy, experimental calculations, radical trapping experiment, and liquid electron spin resonance (ESR) characterization, whereas the existence of OVs was well confirmed by EPR and Raman analyses. Meanwhile, the PPY served as a supporter, and the polaron and bipolaron species of PPY acted as electron and hole acceptors, respectively, which further enhances the charge-carrier transmission and separation in the ternary PZFW15 photocatalyst. The designed ternary nanohybrid (PZFW15) displays outstanding gemifloxacin detoxification (95%, 60 min) and hydrogen generation (657 μmol h^-1), i.e., 1.5 and 2.2 times higher than the normal S-scheme ZFW15 heterostructure and pure ZnFe₂O₄ (ZnF), respectively, with an apparent conversion efficiency of 4.92%. The ESR and trapping experiments indicate that the generated ^•OH and ^•O₂ ^- radicals from the PZFW15 photocatalyst are responsible for gemifloxacin degradation. This unique PPY-supported S-scheme heterojunction is also beneficial for the enhanced electron-transfer rate and provides abundant active sites for photocatalytic reactions.

Electrostatic self-assembly to form unique LiNbO3/ZnS core-shell structure for photocatalytic nitrate reduction enhancement

Photocatalytic NO₃^- reduction in water has been regarded as a promising route due to its high efficiency and green feature. Several limiting factors, such as lack of catalytic sites, insufficient light collection, and spatial charge separation capacity photocatalytic denitrification, still need to be overcome for the practical applications. Herein, an innovative LiNbO₃/ZnS heterojunction with a unilateral opening core-shell structure was constructed. ZnS was tightly anchored on the surface of LiNbO₃ by modified electrostatic self-assembly method. High nitrate removal rate (98.84%) and N₂ selectivity (98.92%) were achieved with a molar ratio of LiNbO₃ and ZnS of 1:5 (1:5L-ZS) using formic acid as a hole scavenge. The LiNbO₃/ZnS degradation kinetics of NO₃^- was corresponding to the first-order kinetics equation. The nitrate removal rate and N₂ selectivity remained stable after three cycles in such photocatalytic NO₃^- reduction. The outstanding photocatalyst performance can be ascribed to the improved surface active sites, the well-matched band structure, and the unique core-shell structure. It provides an effective strategy for controllable fabrication of core-shell photocatalyst with strong light-harvesting ability and charge separation efficiency to enhance the removal rate of nitrate in water.

Bodipy-Containing Porous Microcapsules for Flow Heterogeneous Photocatalysis

Photocatalysis is a facile strategy for complex chemical transformations. Heterogeneous photocatalysis, especially in the flow system, has attracted much attention as it avoids the separation of catalysts. Herein, a kind of a Bodipy-containing porous microcapsule heterogeneous photocatalyst was rationally constructed with modulation on a multiscale. The diiodo-Bodipy with methacrylate (MA-2IBDP) was synthesized as a polymerizable photosensitizer. After immobilization in a polymer matrix, the intersystem crossing rate constant of MA-2IBDP increased to 2.7 × 10¹⁰ s^-1 and its triplet excited-state lifetime prolonged to ∼1 ms. Porous structures in microcapsules were created to facilitate mass transfer. A flat plate flow reactor was constructed to fix the catalytic microcapsules and improve light utilization. With the combination of all the above benefits, the reaction rate constant (0.896 s^-1) is 10 times faster than that of MA-2IBDP in a homogeneous system for juglone synthesis. The continuous production can last for 30 h without yield decrease. The photocatalyst can also be used in aza-Henry reaction, Alder-Ene reaction, and oxidation of thiols to disulfides with conversion rates above 95%. This study provides a means for the construction of heterogeneous catalysts and the flow reaction system.

Sustained CO2-photoreduction activity and high selectivity over Mn, C-codoped ZnO core-triple shell hollow spheres

Solar conversion of CO₂ into energy-rich products is one of the sustainable solutions to lessen the global energy shortage and environmental crisis. Pitifully, it is still challenging to attain reliable and affordable CO₂ conversion. Herein, we demonstrate a facile one-pot approach to design core-triple shell Mn, C-codoped ZnO hollow spheres as efficient photocatalysts for CO₂ reduction. The Mn ions, with switchable valence states, function as “ionized cocatalyst” to promote the CO₂ adsorption and light harvesting of the system. Besides, they can capture photogenerated electrons from the conduction band of ZnO and provide the electrons for CO₂ reduction. This process is continuous due to the switchable valence states of Mn ions. Benefiting from such unique features, the prepared photocatalysts demonstrated fairly good CO₂ conversion performance. This work is endeavoured to shed light on the role of ionized cocatalyst towards sustainable energy production.

Photoreduction of CO₂ into energy-rich products is a sustainable solution to lessen the global energy and environmental crisis. Here the authors show that Mn ions in Mn, C-codoped ZnO hollow spheres function as “ionized cocatalyst” to promote the CO₂ adsorption and light harvesting to boost the CO₂ photoreduction activity.

Boosting Piezo/Photo-Induced Charge Transfer of CNT/Bi4O5I2 Catalyst for Efficient Ultrasound-Assisted Degradation of Rhodamine B

Strain-induced internal electric fields present a significant path to boosting the separation of photoinduced electrons and holes. In addition, piezo-induced positive/negative pairs could be released smoothly, taking advantage of the excellent electroconductibility of some conductors. Herein, the hybrid piezo-photocatalysis is constructed by combining debut piezoelectric nanosheets (Bi4O5I2) and typical conductor multiwalled carbon nanotubes (CNT). The photocatalytic degradation efficiency that the hybrid CNT/Bi4O5I2 exhibits was remarkably increased by more than 2.3 times under ultrasonic vibration, due to the piezo-generated internal electric field. In addition, the transient photocurrent spectroscopy and electrochemical impedance measurement reveal that the CNT coating on Bi4O5I2 enhances the piezo-induced positive/negative migration. Therefore, the piezocatalytic activity of CNT/Bi4O5I2 could be improved by three times, compared with pure Bi4O5I2 nanosheets. Our results may offer promising approaches to sketching efficient piezo-photocatalysis for the full utilization of solar energy or mechanical vibration.

Interfacial chemical bond and internal electric field modulated Z-scheme Sv-ZnIn2S4/MoSe2 photocatalyst for efficient hydrogen evolution

Construction of Z-scheme heterostructure is of great significance for realizing efficient photocatalytic water splitting. However, the conscious modulation of Z-scheme charge transfer is still a great challenge. Herein, interfacial Mo-S bond and internal electric field modulated Z-scheme heterostructure composed by sulfur vacancies-rich ZnIn₂S₄ and MoSe₂ was rationally fabricated for efficient photocatalytic hydrogen evolution. Systematic investigations reveal that Mo-S bond and internal electric field induce the Z-scheme charge transfer mechanism as confirmed by the surface photovoltage spectra, DMPO spin-trapping electron paramagnetic resonance spectra and density functional theory calculations. Under the intense synergy among the Mo-S bond, internal electric field and S-vacancies, the optimized photocatalyst exhibits high hydrogen evolution rate of 63.21 mmol∙g^-1·h^-1 with an apparent quantum yield of 76.48% at 420 nm monochromatic light, which is about 18.8-fold of the pristine ZIS. This work affords a useful inspiration on consciously modulating Z-scheme charge transfer by atomic-level interface control and internal electric field to signally promote the photocatalytic performance.

Interface Engineering of a 2D-C3N4/NiFe-LDH Heterostructure for Highly Efficient Photocatalytic Hydrogen Evolution

Photocatalytic water splitting offers an economic and sustainable pathway for producing hydrogen as a zero-emission fuel, but it still suffers from low efficiencies limited by visible-light absorption capacity and charge separation kinetics. Herein, we report an interface-engineered 2D-C₃N₄/NiFe layered double hydroxide (CN/LDH) heterostructure that shows highly enhanced photocatalytic hydrogen evolution reaction (HER) rate with excellent long-term stability. The morphology and band gap structure of NiFe-LDH are precisely regulated by employing NH₄F as a structure-directing agent, which enables a fine interfacial tuning via coupling with 2D-C₃N₄. The formation of a type II interface in CN/LDH enlarges the active surface area and promotes the charge separation efficiency, leading to an HER rate of 3087 μmol g^-1 h^-1, which is 14 times higher than that of 2D-C₃N₄. This study highlights a rational interface engineering strategy for the formation of a heterostructure with a proper hole transport co-catalyst for designing effective water-splitting photocatalysts.

Rare-Earth-Based Metal-Organic Frameworks as Multifunctional Platforms for Catalytic Conversion

The development of catalytic conversion is very important for human society. In the catalytic process, metal-organic frameworks (MOFs) can be utilized to obtain effective catalysts for their porous structures and adjustable properties. In addition, the introduction of rare-earth (RE) elements with unique properties for catalysts can realize good catalytic performances. Thus, the RE-MOF related catalysts for catalytic conversion are summarized. Due to the cooperation of RE elements and porous MOF structures, the RE-based MOFs can be used as promising catalysts or precursors/supports for other catalysts in the areas of energy conversion, environmental governance, and organic synthesis. These aggregated studies highlight the RE-MOFs as promising candidates for catalytic conversion.

Interfacial Design to Enhance Photocatalytic Hydrogen Evolution via Optimizing Energy and Mass Flows

Energy and mass transfer in photocatalytic systems plays a significant role in photocatalytic water splitting, but relevant research has long been ignored. Here, an interfacial photocatalytic mode for photocatalytic hydrogen production is exploited to optimize the energy and mass flows and mainly includes a heat-insulating layer, a water-channel layer, and a photothermal photocatalytic layer. In this mode, the energy flow is optimized for efficient spreading, conversion, and utilization. A low-loss path (ultrathin water film) and an efficient heat localized zone are constructed, where light energy, especially infrared-light energy, can transfer to the target functional membrane surface with low loss and the thermal energy converted from light can be localized for further use. Meanwhile, the optimization of the mass flow is achieved by improving the desorption capacity of the products. The generated hydrogen bubbles can rapidly leave from the surface of the photocatalyst, along with the active sites being released timely. Consequently, the photocatalytic hydrogen production rate can be increased up to about 6.6 times that in a conventional photocatalytic mode. From the system design aspect, this work provides an efficient strategy to improve the performance of photocatalytic water splitting by optimizing the energy and mass flows.

Beyond the Visible: Bioinspired Infrared Adaptive Materials

Infrared (IR) adaptation phenomena are ubiquitous in nature and biological systems. Taking inspiration from natural creatures, researchers have devoted extensive efforts for developing advanced IR adaptive materials and exploring their applications in areas of smart camouflage, thermal energy management, biomedical science, and many other IR-related technological fields. Herein, an up-to-date review is provided on the recent advancements of bioinspired IR adaptive materials and their promising applications. First an overview of IR adaptation in nature and advanced artificial IR technologies is presented. Recent endeavors are then introduced toward developing bioinspired adaptive materials for IR camouflage and IR radiative cooling. According to the Stefan-Boltzmann law, IR camouflage can be realized by either emissivity engineering or thermal cloaks. IR radiative cooling can maximize the thermal radiation of an object through an IR atmospheric transparency window, and thus holds great potential for use in energy-efficient green buildings and smart personal thermal management systems. Recent advances in bioinspired adaptive materials for emerging near-IR (NIR) applications are also discussed, including NIR-triggered biological technologies, NIR light-fueled soft robotics, and NIR light-driven supramolecular nanosystems. This review concludes with a perspective on the challenges and opportunities for the future development of bioinspired IR adaptive materials.

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.

Photocatalysis Enhanced by External Fields

The efficient conversion of solar energy by means of photocatalysis shows huge potential to relieve the ongoing energy crisis and increasing environmental pollution. However, unsatisfactory conversion efficiency still hinders its practical application. The introduction of external fields can remarkably enhance the photocatalytic performance of semiconductors from the inside out. This review focuses on recent advances in the application of diverse external fields, including microwaves, mechanical stress, temperature gradient, electric field, magnetic field, and coupled fields, to boost photocatalytic reactions, for applications in, for example, contaminant degradation, water splitting, CO₂ reduction, and bacterial inactivation. The relevant reinforcement mechanisms of photoabsorption, the transport and separation of photoinduced charges, and adsorption of reagents by the external fields are highlighted. Finally, the challenges and outlook for the development of external-field-enhanced photocatalysis are presented.

Core–shell carbon colloid sphere@phosphotungstic acid/CdS as a Z-scheme heterojunction with synergistic adsorption, photothermal and photocatalytic performance

Core–shell carbon colloid sphere@phosphotungstic acid/CdS exhibits excellent visible-light-driven photocatalytic performance, which is due to the Z-scheme heterojunction favoring the charge transfer and spatial charge separation and the photothermal effect.

Construction of Bi/Bi5O7I anchored on a polymer with boosted interfacial charge transfer for biofouling resistance and photocatalytic H2 evolution

The prepared coatings possess hydrogen production, antifouling performance, self-cleaning properties, this strategy can be a promising candidate to restrict biofouling and photocatalytic hydrogen production for marine coating applications.

Fabrication of CdS Frame-in-Cage Particles for Efficient Photocatalytic Hydrogen Generation under Visible-Light Irradiation

The design of advanced structures for semiconductor photocatalysts is an effective approach to enhance their performance toward solar-to-chemical energy conversion. Hollow and frame-like structures show advantageous features for photocatalytic reactions with enlarged surface area, shortened charge-transfer distance, promoted light-absorption ability, and enhanced mass-transfer capability. Here, a facile two-step sulfidation strategy is developed to fabricate unique CdS frame-in-cage particles for photocatalytic hydrogen generation. Cd-based Prussian blue analog (Cd-PBA) cubes are first converted to Cd-PBA cube-in-CdS cage particles, which are further transformed to CdS frame-in-cage particles. Benefiting from the novel frame-in-cage structure, the obtained CdS photocatalyst exhibits high activity under visible-light irradiation with the hydrogen generation rate of 13.6 mmol h^-1 g^-1 , which is much enhanced compared with those of the CdS cubes and cages.

Sustainable Internal Electric Field for Enhanced Photocatalysis: From Material Design to Energy Utilization

The intrinsic internal electric field in a ferroelectric photocatalyst is beneficial for improving the photocatalytic properties because of its positive effect on the separation and migration of photogenerated carriers. However, this kind of internal electric field is static and easily saturated by inner and outer shielding effects, seriously restricting its potential in photocatalysis. To overcome this problem, a sustainable internal electric field was introduced into photocatalysis based on piezoelectric and pyroelectric effect, which exhibits good capability in consistently boosting photocatalytic activity, thus becoming a hot research topic. In this Perspective we summarize the recent significant progress in the construction of sustainable internal electric fields for facilitating photocatalysis from material design to energy utilization. Moreover, the fascinating influence of sustainable internal electric fields on carrier behavior is also discussed. Finally, a summary and outlook for building a sustainable internal electric field to further enhance photocatalytic performance are provided.

Z-scheme CdS/Co9S8-RGO for photocatalytic hydrogen production

All-solid-state Z-scheme CdS/Co₉S₈-RGO heterostructures are synthesized by a facile one-pot hydrothermal method followed by annealing, which exhibit a H₂ evolution rate up to 4.82 mmol h⁻¹ g⁻¹ and a remarkable stability due to an efficient charge transfer and separation.