Photoinduced Defect Engineering: Enhanced Photothermal Catalytic Performance of 2D Black In2 O3- x Nanosheets with Bifunctional Oxygen Vacancies

Elucidating CO2 Hydrogenation over In2 O3 Nanoparticles using Operando UV/Vis and Impedance Spectroscopies

In2 O3 has emerged as a promising catalyst for CO2 activation, but a fundamental understanding of its mode of operation in CO2 hydrogenation is still missing, as the application of operando vibrational spectroscopy is challenging due to absorption effects. In this mechanistic study, we systematically address the redox processes related to the reverse water-gas shift reaction (rWGSR) over In2 O3 nanoparticles, both at the surface and in the bulk. Based on temperature-dependent operando UV/Vis spectra and a novel operando impedance approach for thermal powder catalysts, we propose oxidation by CO2 as the rate-determining step for the rWGSR. The results are consistent with redox processes, whereby hydrogen-containing surface species are shown to exhibit a promoting effect. Our findings demonstrate that oxygen/hydrogen dynamics, in addition to surface processes, are important for the activity, which is expected to be of relevance not only for In2 O3 but also for other reducible oxide catalysts.

Recent Advancements in Photocatalysis Coupling by External Physical Fields

Photocatalysis is one of the most promising green technologies to utilize solar energy for clean energy achievement and environmental governance, such as artificial photosynthesis, water splitting, pollutants degradation, etc. Despite decades of research, the performance of photocatalysis still falls far short of the requirement of 5% solar energy conversion efficiency. Combining photocatalysis with the other physical fields has been proven to be an efficient way around this barrier which can improve the performance of photocatalysis remarkably. This review will focus on the recent advances in photocatalysis coupling by external physical fields, including Thermal-coupled photocatalysis (TCP), Mechanical-coupled photocatalysis (MCP), and Electromagnetism-coupled photocatalysis (ECP). In this paper, coupling mechanisms, materials, and applications of external physical fields are reviewed. Specifically, the promotive effect on photocatalytic activity by the external fields is highlighted. This review will provide a detailed and specific reference for photocatalysis coupling by external physical fields in a deep-going way.

Nanomaterial-enabled photothermal-based solar water disinfection processes: Fundamentals, recent advances, and mechanisms

The pathogenic microorganisms in water pose a great threat to human health. Photothermal and photothermocatalytic disinfection using nanomaterials (NPs) has offered a promising and effective strategy to address the challenges in solar water disinfection (SODIS), especially in the point-of-use operations. This review aims at providing comprehensive and state-of-the-art knowledge of photothermal-based disinfection by NPs. The fundamentals and principles of photothermal-based disinfection were first introduced. Then, recent advances in developing photothermal/photothermocatalytic catalysts were systematically summarized. The light-to-heat conversion and disinfection performance of a large variety of photothermal materials were presented. Given the complicated mechanisms of photothermal-based disinfection, the attacks from reactive oxygen species and heat, the destruction of bacterial cells, and the antibacterial effects of released metal ions were highlighted. Finally, future challenges and opportunities associated with the development of cost-effective photothermal/photothermocatalytic disinfection systems were outlined. This review will provide guidance in designing future NPs and inspire more research efforts from environmental nano-communities to move towards practical water disinfection operations.

MOF-Transformed In2O3-x@C Nanocorn Electrocatalyst for Efficient CO2 Reduction to HCOOH

For electrochemical CO2 reduction to HCOOH, an ongoing challenge is to design energy efficient electrocatalysts that can deliver a high HCOOH current density (JHCOOH) at a low overpotential. Indium oxide is good HCOOH production catalyst but with low conductivity. In this work, we report a unique corn design of In2O3-x@C nanocatalyst, wherein In2O3-x nanocube as the fine grains dispersed uniformly on the carbon nanorod cob, resulting in the enhanced conductivity. Excellent performance is achieved with 84% Faradaic efficiency (FE) and 11 mA cm-2 JHCOOH at a low potential of - 0.4 V versus RHE. At the current density of 100 mA cm-2, the applied potential remained stable for more than 120 h with the FE above 90%. Density functional theory calculations reveal that the abundant oxygen vacancy in In2O3-x has exposed more In3+ sites with activated electroactivity, which facilitates the formation of HCOO* intermediate. Operando X-ray absorption spectroscopy also confirms In3+ as the active site and the key intermediate of HCOO* during the process of CO2 reduction to HCOOH.

Photothermal synthesis of a CuO x &FeO y catalyst with a layered double hydroxide-derived pore-confined frame to achieve photothermal CO2 hydrogenation to CO with a rate of 136 mmol min-1 gcat -1

Solar-driven CO₂ conversion into the industrial chemical CO via the reverse water-gas reaction is an ideal technological approach to achieve the key step of carbon neutralization. The high reaction temperature is cost-free due to the photothermal conversion brought about by solar irradiation and is beneficial to the catalytic efficiency. However, the thermostability of adopted catalysts is a great challenge. Herein, we develop an in situ photothermal synthesis to obtain a CuO _x &FeO _y catalyst with a layered double hydroxide-derived pore-confined frame. The optimized sample delivers a CO generation rate of 136.3 mmol min^-1 g_cat ^-1 with the selectivity of ∼100% at a high reaction temperature of 1015 °C. The efficient catalytic activity can be attributed to the fact that the pore-confined frame substrate prevents the growth of CuO _x and FeO _y nanoparticles during the high-temperature reaction and the basic groups on the substrate promote the adsorption and activation of CO₂.

Tensile-Strained Palladium Nanosheets for Synthetic Catalytic Therapy and Phototherapy

Palladium nanosheets (Pd NSs) are well-investigated photothermal therapy agents, but their catalytic potential for tumor therapy has been underexplored owing to the inactive dominant (111) facets. Herein, lattice tensile strain is introduced by surface reconstruction to activate the inert surface, endowing the strained Pd NSs (SPd NSs) with photodynamic, catalase-like, and peroxidase-like properties. Tensile strain promoting the photodynamic and enzyme-like activities is revealed by density functional theory calculations. Compared with Pd NSs, SPd NSs exhibit lower photothermal effect, but approximately five times higher tumor inhibition rate. This work calls for further study to activate nanomaterials by strain engineering and surface reconstruction for catalytic therapy of tumors.

Band structure alignment transitioning strategy for the fabrication of efficient photocatalysts for solar fuel generation and environmental remediation applications

Indium hydroxide (In(OH)₃) and indium oxide (In₂O₃) have proven to be efficient catalysts for photocatalytic water-splitting reactions to produce hydrogen (H₂) and for organic pollutant degradation applications. However, the limited optical absorption features of indium-based nanostructures have restricted their practical applications. In this study, we have successfully designed indium hydroxide- and indium oxide-loaded metal sulfide (cadmium sulfide, CdS) heterostructures as excellent photocatalytic systems for photocatalytic hydrogen evolution and tetracycline hydrochloride pollutant degradation reactions. In this system, In(OH)₃ and In₂O₃ established Type-I and S-scheme heterojunctions, respectively, with CdS, resulting in superior charge separation properties and outstanding photocatalytic activity. Specifically, the rational and appropriate design of the aforementioned indium-based heterostructures promoted the separation of photoexcited charge carriers via Type-I and S-scheme paths. Accordingly, enhanced photocatalytic H₂ evolution activities of 9.58 and 14.98 mmol·g^-1·h^-1 were achieved for CdS-In(OH)₃ and CdS-In₂O₃, respectively. Furthermore, the highest degradation efficiency of CdS-In₂O₃ was ∼ 90%, which was higher than those of CdS-In(OH)₃ (72%) and bare CdS nanorods (51%). Therefore, the results of this study provide an opportunity to enhance the catalytic activities of heterostructured photocatalytic systems by utilizing the strategy of transitioning band structure alignment from the Type-I to the S-scheme.

A Stacked Plasmonic Metamaterial with Strong Localized Electric Field Enables Highly Efficient Broadband Light-Driven CO2 Hydrogenation

Light utilization largely governs the performance of CO₂ photoconversion, whereas most of the materials that are implemented in such an application are restricted in a narrow spectral absorption range. Plasmonic metamaterials with a designable regular pattern and facile tunability are excellent candidates for maximizing light absorption to generate substantial hot electrons and thermal energy. Herein, a concept of coupling a Au-based stacked plasmonic metamaterial with single Cu atoms in alloy, as light absorber and catalytic sites, respectively, is reported for gas-phase light-driven catalytic CO₂ hydrogenation. The metamaterial structure works in a broad spectral range (370-1040 nm) to generate high surface temperature for photothermal catalysis, and also induces strong localized electric field in favor of transfer of hot electrons and reduced energy barrier in CO₂ hydrogenation. This work unravels the significant role of a strong localized electric field in photothermal catalysis and demonstrates a scalable fabrication approach to light-driven catalysts based on plasmonic metamaterials.

Subsurface oxygen defects electronically interacting with active sites on In2O3 for enhanced photothermocatalytic CO2 reduction

Oxygen defects play an important role in many catalytic reactions. Increasing surface oxygen defects can be done through reduction treatment. However, excessive reduction blocks electron channels and deactivates the catalyst surface due to electron-trapped effects by subsurface oxygen defects. How to effectively extract electrons from subsurface oxygen defects which cannot directly interact with reactants is challenging and remains elusive. Here, we report a metallic In-embedded In2O3 nanoflake catalyst over which the turnover frequency of CO2 reduction into CO increases by a factor of 866 (7615 h-1) and 376 (2990 h-1) at the same light intensity and reaction temperature, respectively, compared to In2O3. Under electron-delocalization effect of O-In-(O)Vo-In-In structural units at the interface, the electrons in the subsurface oxygen defects are extracted and gather at surface active sites. This improves the electronic coupling with CO2 and stabilizes intermediate. The study opens up new insights for exquisite electronic manipulation of oxygen defects.

Photodriven CO2 Hydrogenation into Diverse Products: Recent Progress and Perspective

Converting CO2 into value-added chemicals through hydrogenation can optimize the energy structure dominated by fossil energy, effectively alleviate environmental problems, and achieve full utilization of carbon resources. However, the traditional CO2 hydrogenation reactions need to be carried out under high temperature and pressure, causing inevitable secondary pollution to the environment. A fundamental way to solve these problems is to use clean solar energy to convert CO2 into value-added chemicals and to establish an artificial carbon cycle process. In this Perspective, we highlight recent advances in photodriven CO2 conversion, including the reverse water-gas-shift reaction, methanation reaction, methanol synthesis reaction, and C2+ hydrocarbon synthesis reaction. Finally, we also discuss the challenges and future investigation opportunities for modulating the selective conversion of CO2. This Perspective offers guidance for the design of photodriven CO2 conversion or even the entire C1 catalyst chemistry for tuning product selectivity and activity.

Direct Conversion of CO2 into Hydrocarbon Solar Fuels by a Synergistic Photothermal Catalysis

Photothermal coupling catalysis technology has been widely studied in recent years and may be a promising method for CO2 reduction. Photothermal coupling catalysis can improve chemical reaction rates and realize the controllability of reaction pathways and products, even in a relatively moderate reaction condition. It has inestimable value in the current energy and global environmental crisis. This review describes the application of photothermal catalysis in CO2 reduction from different aspects. Firstly, the definition and advantages of photothermal catalysis are briefly described. Then, different photothermal catalytic reductions of CO2 products and catalysts are introduced. Finally, several strategies to improve the activity of photothermal catalytic reduction of CO2 are described and we present our views on the future development and challenges of photothermal coupling. Ultimately, the purpose of this review is to bring more researchers’ attention to this promising technology and promote this technology in solar fuels and chemicals production, to realize the value of the technology and provide a better path for its development.

Anchoring Platinum Clusters onto Oxygen Vacancy-Modified In2O3 for Ultraefficient, Low-Temperature, Highly Sensitive, and Stable Detection of Formaldehyde

To avoid carcinogenicity, formaldehyde gas, currently being only detected at higher operating temperatures, should be selectively detected in time with ppb concentration sensitivity in a room-temperature indoor environment. This is achieved in this work through introducing oxygen vacancies and Pt clusters on the surface of In₂O₃ to reduce the optimal operating temperature from 120 to 40 °C. Previous studies have shown that only water participates in the competitive adsorption on the sensor surface. Here, we experimentally confirm that the adsorbed water on the fabricated sensor surface is consumed via a chemical reaction due to the strong interaction between the oxygen vacancies and Pt clusters. Therefore, the long-term stability of formaldehyde gas detection is improved. The results of theoretical calculations in this work reveal that the excellent formaldehyde gas detection of Pt/In₂O_3-x originates from the electron enrichment due to the surface oxygen vacancies and the molecular adsorption and activation ability of Pt clusters on the surface. The developed Pt/In₂O_3-x sensor has potential use in the ultraefficient, low-temperature, highly sensitive, and stable detection of indoor formaldehyde at an operating temperature as low as room temperature.

Tailoring S-vacancy concentration changes the type of the defect and photocatalytic activity in ZFS

Defect engineering is crucial in the development of semiconductor catalyst activity. However, the influence of defect/vacancy density and states on catalysis remains vague. Thus, the optimized sulfur vacancy (S_V) state is achieved among Fe-ZnS models (ZFS) via a chemical etching strategy for photocatalytic degradation (PD). As the S_V concentration (ρS_V) increases, the predominant state of vacancies changes from isolated defects－a state to a combination of a state and vacancy clusters－e state, as verified by positron annihilation and X-ray absorption fine structure spectra. However, the two types of defect states activated the intrinsic activity of the crystal via radically different mechanisms and exerted different degrees of influence on PD activity, as revealed by first-principles calculations and quantitative structure-activity relationship. Our results suggest that the S_V activity is strongly influenced by its concentration in the ZFS crystal, while the vacancy concentration is not a control parameter for the PD activity, but a defect form. The underlying essence of atomic defects behavior affecting crystal catalytic activity at the atomic level is also revealed in this paper. Uncovering these structural relationships provide a theoretical basis for designing effective catalysts.

Thermo-photo catalysis: a whole greater than the sum of its parts

Thermo-photo catalysis, which is the catalysis with the participation of both thermal and photo energies, not only reduces the large energy consumption of thermal catalysis but also addresses the low efficiency of photocatalysis. As a whole greater than the sum of its parts, thermo-photo catalysis has been proven as an effective and promising technology to drive chemical reactions. In this review, we first clarify the definition (beyond photo-thermal catalysis and plasmonic catalysis), classification, and principles of thermo-photo catalysis and then reveal its superiority over individual thermal catalysis and photocatalysis. After elucidating the design principles and strategies toward highly efficient thermo-photo catalytic systems, an ample discussion on the synergetic effects of thermal and photo energies is provided from two perspectives, namely, the promotion of photocatalysis by thermal energy and the promotion of thermal catalysis by photo energy. Subsequently, state-of-the-art techniques applied to explore thermo-photo catalytic mechanisms are reviewed, followed by a summary on the broad applications of thermo-photo catalysis and its energy management toward industrialization. In the end, current challenges and potential research directions related to thermo-photo catalysis are outlined.

New black indium oxide—tandem photothermal CO2-H2 methanol selective catalyst

It has long been known that the thermal catalyst Cu/ZnO/Al₂O₃(CZA) can enable remarkable catalytic performance towards CO₂ hydrogenation for the reverse water-gas shift (RWGS) and methanol synthesis reactions. However, owing to the direct competition between these reactions, high pressure and high hydrogen concentration (≥75%) are required to shift the thermodynamic equilibrium towards methanol synthesis. Herein, a new black indium oxide with photothermal catalytic activity is successfully prepared, and it facilitates a tandem synthesis of methanol at a low hydrogen concentration (50%) and ambient pressure by directly using by-product CO as feedstock. The methanol selectivities achieve 33.24% and 49.23% at low and high hydrogen concentrations, respectively.

Harsh reaction conditions are generally required for CO2 hydrogenation to shift the thermodynamic equilibrium towards methanol synthesis. Here, a new black indium oxide with two types of active sites, frustrated Lewis pairs and oxygen vacancies, is prepared, and facilitates a tandem synthesis of methanol at a low hydrogen concentration (50%) and ambient pressure.

Subnanometric alkaline-earth oxide clusters for sustainable nitrate to ammonia photosynthesis

The limitation of inert N2 molecules with their high dissociation energy has ignited research interests in probing other nitrogen-containing species for ammonia synthesis. Nitrate ions, as an alternative feedstock with high solubility and proton affinity, can be facilely dissociated for sustainable ammonia production. Here we report a nitrate to ammonia photosynthesis route (NO3-RR) catalyzed by subnanometric alkaline-earth oxide clusters. The catalyst exhibits a high ammonia photosynthesis rate of 11.97 mol gmetal-1 h-1 (89.79 mmol gcat-1 h-1) with nearly 100% selectivity. A total ammonia yield of 0.78 mmol within 72 h is achieved, which exhibits a significant advantage in the area of photocatalytic NO3-RR. The investigation of the molecular-level reaction mechanism reveals that the unique active interface between the subnanometric clusters and TiO2 substrate is beneficial for the nitrate activation and dissociation, contributing to efficient and selective nitrate reduction for ammonia production with low energy input. The practical application of NO3-RR route in simulated wastewater is developed, which demonstrates great potential for its industrial application. These findings are of general knowledge for the functional development of clusters-based catalysts and could open up a path in the exploitation of advanced ammonia synthesis routes with low energy consumption and carbon emission.

Photothermal Chemistry Based on Solar Energy: From Synergistic Effects to Practical Applications

With the development of society, energy shortage and environmental problems have become more and more outstanding. Solar energy is a clean and sustainable energy resource, potentially driving energy conversion and environmental remediation reactions. Thus, solar-driven chemistry is an attractive way to solve the two problems. Photothermal chemistry (PTC) is developed to achieve full-spectral utilization of the solar radiation and drive chemical reactions more efficiently under relatively mild conditions. In this review, the mechanisms of PTC are summarized from the aspects of thermal and non-thermal effects, and then the interaction and synergy between these two effects are sorted out. In this paper, distinguishing and quantifying these two effects is discussed to understand PTC processes better and to design PTC catalysts more methodically. However, PTC is still a little far away from practical. Herein, several key points, which must be considered when pushing ahead with the engineering application of PTC, are proposed, along with some workable suggestions on the practical application. This review provides a unique perspective on PTC, focusing on the synergistic effects and pointing out a possible direction for practical application.

Insights into Photothermally Enhanced Photocatalytic U(VI) Extraction by a Step-Scheme Heterojunction

In this work, a CdS/BiVO 4 step-scheme (S-scheme) heterojunction with self-photothermally enhanced photocatalytic effect was synthesized and applied for efficient U(VI) photoextraction. Characterizations such as transient absorption spectroscopy and Tafel test together confirmed the formation of S-scheme heterojunctions, which allows CdS/BiVO 4 to avoid photocorrosion while retaining the strong reducing capacity of CdS and the oxidizing capacity of BiVO 4 . Experimental results such as radical quenching experiments and electron spin resonance show that U(VI) is rapidly oxidized by photoholes/ • OH to insoluble UO 2 (OH) 2 after being reduced to U(IV) by photoelectrons/ • O 2 - , which precisely avoids the depletion of electron sacrificial agents. The rapid recombination of electron-hole pairs triggered by the S-scheme heterojunction is found to release large amounts of heat and accelerate the photocatalysis. This work offers a new enhanced strategy for photocatalytic uranium extraction and presents a direction for the design and development of new photocatalysts.

Photo-Fenton and oxygen vacancies' synergy for enhancing catalytic activity with S-scheme FeS2/Bi2WO6 heterostructure

A series of FeS2/Bi2WO6 S-scheme photo-Fenton catalysts with efficient catalytic performances were successfully prepared by coupling FeS2 into the surface oxygen vacancy enriched Bi2WO6 using calcination and solvothermal methods.

Bismuth single atom supported CeO2 nanosheets for oxidation resistant photothermal reverse water gas shift reaction

Bi single atoms supported on CeO2 nanosheets combined with a Ti2O3 based photothermal device showed oxidation resistance and outperforming weak solar driven RWGS with a CO production rate of 31.00 mmol g−1 h−1 under 3 sun units of irradiation.

In2S3 nanoparticles coupled to In-MOF nanorods: The structural and electronic modulation for synergetic photocatalytic degradation of Rhodamine B

Enhancing photocatalytic performance via electronic modulation have attracted much attention for synergetic photocatalytic degradation of antibiotic pollutant. In this study, a new hetero-structured system is raised, which comprises In₂S₃ coupled to In-MOF and operates as an efficient photocatalyst for RhB degradation. The formation of hetero-structure and occurred electron modulation of In₂S₃/In-MOF hybrid was confirmed by relevant characterizations. Surprisingly, the In₂S₃/In-MOF hybrid represented enhanced photocatalytic ability over In-MOF. The photocatalysis of Rhodamine B in presence of In₂S₃/In-MOF hybrid has achieved 92.2 % degradation.

Synergetic modulation of surface alkali and oxygen vacancy over SrTiO3for the CO2photodissociation

Photochemical conversion of CO₂into solar fuels is one of the promising strategies to reducing the CO₂emission and developing a sustainable carbon economy. For the more efficient utilization of solar spectrum, several approaches were adopted to pursue the visible-light-driven SrTiO₃. Herein, oxygen vacancy was introduced over the commercial SrTiO₃(SrTiO_3-x) via the NaBH₄thermal treatment, to extend the light absorption and promote the CO₂adsorption over SrTiO₃. Due to the mid-gap states resulted from the oxygen deficiency, combined with the intrinsic energy level of SrTiO₃, the SrTiO_3-xcatalyst exhibited excellent CO productivity (4.1 μmolˑg^-1ˑh^-1) and stability from the CO₂photodissociation under the visible-light irradiation (λ > 400 nm). Then, surface alkalization over SrTiO_3-x(OH-SrTiO_3-x) was carried out to further enhance the CO₂adsorption/activation over the surface base sites and provide the OH ions as hole acceptor, the surface alkali OH connected with Sr site of SrTiO₃could also weaken the Sr-O bonding thus facilitate the regeneration of surface oxygen vacancy under the light illumination, thus resulting in 1.5 times higher CO productivity additionally. This study demonstrates that the synergetic modulation of alkali OH and oxygen vacancy over SrTiO₃could largely promote the CO₂photodissociation activity.

Molecular bixbyite-like In12-oxo clusters with tunable functionalization sites for lithography patterning applications

Indium oxides have been widely applied in many technological areas, but their utilization in lithography has not been developed. Herein, we illustrated a family of unprecedented In₁₂-oxo clusters with a general formula [In₁₂(μ₄-O)₄(μ₂-OH)₂(OCH₂CH₂NHCH₂CH₂O)₈(OR)₄X₄]X₂ (where X = Cl or Br; R = CH₃, C₆H₄NO₂ or C₆H₄F), which not only present the largest size record in the family of indium-oxo clusters (InOCs), but also feature the first molecular model of bixbyite-type In₂O₃. Moreover, through the labile coordination sites of the robust diethanolamine-stabilized In₁₂-oxo core, these InOCs can be accurately functionalized with different halides and alcohol or phenol derivatives, producing tunable solubility. Based on the high solution stability as confirmed by ESI-MS analysis, homogeneous films can be fabricated using these In₁₂-oxo clusters by the spin-coating method, which can be further used for electron beam lithography (EBL) patterning studies. Accordingly, the above structural regulations have significantly influenced their corresponding film quality and patterning performance, with bromide or p-nitrophenol functionalized In₁₂-oxo clusters displaying better performance of sub-50 nm lines. Thus, the here developed bixbyite-type In₁₂-oxo cluster starts the research on indium-based patterning materials and provides a new platform for future lithography radiation mechanism studies.

Bixbyite-like In₁₂-oxo clusters with labile coordination sites show tunable solubility, varying film quality and distinct lithography patterning performance.

Spinel-Oxide-Integrated BiVO4 Photoanodes with Photothermal Effect for Efficient Solar Water Oxidation

Spinel oxide materials have been widely used as oxygen evolution catalysts to enhance the photoelectrochemical (PEC) performance of photoelectrodes. Herein, we demonstrate that the water splitting efficiency of a photoanode can be further enhanced by introducing its photothermal effect. Under near-infrared radiation, the temperature of the NiCo₂O₄/BiVO₄ photoanode increases moderately, leading to improved water oxidation kinetics and charge transport simultaneously. With the assistance of the photothermal effect, the obtained photoanode reaches a photocurrent density of 6.20 mA cm^-2 at 1.23 V vs reversible hydrogen electrode. A series of spinel-type MCo₂O₄ oxides (M = Mn, Zn, Cu, and Fe) are deposited on the surface of the BiVO₄ photoanode to show similar photothermally enhanced PEC performance. The research discovery provides a way for improving the catalytic activity of photoanode materials with a photothermal effect, which may be applied to various fields of energy conversion, including CO₂ reduction, N₂ fixation, and pollutant degradation.

Boosting the photothermal performance of vacancy-rich MoSe2-x nanoflowers for photoacoustic imaging guided tumor chemo-photothermal therapy

Due to the relatively low photo-thermal conversion efficiency and poor tumor targeting capacity, phototheranostic nanoagents encounter some challenges in cancer photothermal therapy. To address this problem, in the current research we developed vacancy-rich MoSe_2-x (0 ≤ x ≤ 1) nanoflowers (MNFs) with molecular 2-deoxy-D-glucose (2-DG) as the activity target, which could be used as a novel phototheranostic nanoagent in the photoacoustic imaging guided chemo-photothermal synergistic therapy. This selenium-deficient structure endows MNFs with high photothermal conversion efficiency (41.7%) due to the strong localized surface plasmon resonances. Besides, the surface linked 2-DG molecules and the flower-like morphology in the nanoagents promoted the targeting effect (active and passive), thus facilitating the efficient concentration of the nanoagents within the tumor site. Both in vitro and in vivo anti-tumor experiments have demonstrated the high synergistic efficacy promoted by MNFs and complete tumor eradication with lower administration dosages could be achieved. This rational design of nanoparticles not only provided the paradigm of high therapeutic efficacy of a chemo-photothermal protocol for precise cancer theranostics, but also expanded the scope of nanomedical applications using semiconductor-based nanoplatforms through well-defined designing of their microstructures and physiochemical properties.

Highly Active PdO/Mn3 O4 /CeO2 Nanocomposites Supported on One Dimensional Halloysite Nanotubes for Photoassisted Thermal Catalytic Methane Combustion

In this work, we have successfully triggered the aqueous auto-redox reactions between reductive Ce(OH)₃ and oxidative MnO₄ ^- /Pd²⁺ ions to form PdO/Mn₃ O₄ /CeO₂ (PMC) nanocomposites. PMC could spontaneously self-assemble into compact encapsulation on the surface of halloysite nanotubes (HNTs) to form the final one dimensional HNTs supported PMCs (HPMC). It is identified that there exists strong synergistic effects among the components of PdO, Mn₃ O₄ , and CeO₂ , and hence HPMC could show excellent performance on photoassisted thermal catalytic CH₄ combustion that its light-off temperature was sharply reduced to be 180 °C under visible light irradiation. Based on detailed studies, it is found that the catalytic reaction process well follows the classic MVK mechanism, and adsorption/activation of O₂ into active oxygen species (O*) should be the rate-determining step for CH₄ conversion.

Black SnO2-x based nanotheranostic for imaging-guided photodynamic/photothermal synergistic therapy in the second near-infrared window

The shallow penetration depth of photothermal agents in the first near-infrared (NIR-I) window significantly limits their therapeutic efficiency. Multifunctional nanotheranostic agents in the second near-infrared (NIR-II) window have drawn extensive attention for their combined treatment of tumors. Here, for the first time, we created oxygen-deficient black SnO_2-x with strong NIR (700-1200 nm) light absorption with NaBH₄ reduction from white SnO₂. Hyaluronic acid (HA) could selectively target cancer cells overexpressed CD44 protein. After modification with HA, the obtained nanotheranostic SnO_2-x@SiO₂-HA showed high dispersity in aqueous solution and good biocompatibility. SnO_2-x@SiO₂-HA was confirmed to simultaneously generate enough hyperthermia and reactive oxygen species with single NIR-II (1064 nm) light irradiation. Because HA is highly affined to CD44 protein, SnO_2-x@SiO₂-HA has specific uptake by overexpressed CD44 cells and can be accurately transferred to the tumor site. Furthermore, tumor growth was significantly inhibited following synergistic photodynamic therapy (PDT) and photothermal therapy (PTT) with targeted specificity under the guidance of photoacoustic (PA) imaging using 1064 nm laser irradiation in vivo. Moreover, SnO_2-x@SiO₂-HA accelerated wound healing. This work prominently extends the therapeutic utilization of semiconductor nanomaterials by changing their nanostructures and demonstrates for the first time that SnO_2-x based therapeutic agents can accelerate wound healing. STATEMENT OF SIGNIFICANCE: The phototherapeutic efficacy of nanotheranostics by NIR-I lightirradiation was restricted owing to the limitation of tissue penetration and maximum permissible exposure. To overcome these limitations, we hereby fabricated a NIR-IIlight-mediated multifunctional nanotheranostic based on SnO₂-x. The introduction of oxygen vacancy strategy was employed to construct full spectrum responsive oxygen-deficient SnO2-x, endowing outstanding photothermal conversion, and remarkable production activity of reactive oxygen species under NIR-II light activation. Tumor growth was significantly inhibited following synergistic PDT/PTT with targeted specificity under the guidance of photoacoustic imaging using 1064 nm laser irradiation in vivo. Our strategy not only expands the biomedical application of SnO₂, but also providea method to develop other inorganic metal oxide-based nanosystems for NIR-II light-activated phototheranostic of cancers.

Core-shell ZIF-8@MIL-68(In) derived ZnO nanoparticles-embedded In2O3 hollow tubular with oxygen vacancy for photocatalytic degradation of antibiotic pollutant

Developing a novel core-multishelled metal oxide hollow tube with rich oxygen vacancy is highly attractive in photocatalytic degradation of antibiotic pollutant. Herein, ZnO@In₂O₃ core-shell hollow microtubes were synthesized via one-step calcination of ZIF-8@MIL-68(In) formed by an in-situ self-assembly. TEM images demonstrate that 0D ZnO quantum dots (QDs) shell with 0.2 µm were well coated on the surface of 1D In₂O₃ hollow tube as the core with 1.2 µm. The synthesized heterostructure indicates the enhanced photocatalytic performance in tetracycline (TC) degradation compared with single ZIF-derived ZnO and MIL-68(In)-derived In₂O₃ under simulated solar irradiation. Besides, organic pollutants including malachite green (MG), methylene blue (MB) and rhodamine B (RhB) are further used to evaluate the photocatalytic activity of ZnO@In₂O₃, and the effect of weight ratios between ZnO and In₂O₃ on degradation efficiency is also studies. The ZnO@In₂O₃ heterojunction can provide higher specific surface area, expose more active sites, possess appropriate number of oxygen vacancies, enhance light absorption and further effectively boost the transfer and separation of photoinduced charge carriers. In addition, the proposed photocatalytic mechanism and degradation pathway are discussed in detail based on active species trapping test, electron spin resonance (ESR) and LCMS.

Defect Engineering of Photocatalysts towards Elevated CO2 Reduction Performance

Photocatalytic CO₂ reduction provides a promising solution to address the crises of massive CO₂ emissions and fossil energy shortages. As one of the most effective strategies to promote CO₂ photoconversion, defect engineering shows great potential in modulating the electronic structure and light absorption properties of photocatalysts while increasing surface active sites for CO₂ activation and conversion. This Review summarizes the recent progress in defect engineering of photocatalysts to promote CO₂ reduction performances from the following four aspects: 1) Approaches to defect (mainly vacancy and dopant) generation in photocatalysts; 2) defect structure characterization techniques; 3) physical and chemical properties of defect-engineered photocatalysts; 4) CO₂ reduction performance enhancements in activity, selectivity, and stability of photocatalysts by defect engineering. This Review is expected to present readers with a comprehensive view of progress in the field of photocatalytic CO₂ reduction through defect engineering for elevated CO₂ -to-fuels conversion efficiency.

Defect Engineering Enables Synergistic Action of Enzyme-Mimicking Active Centers for High-Efficiency Tumor Therapy

Perusing redox nanozymes capable of disrupting cellular homeostasis offers new opportunities to develop cancer-specific therapy, but remains challenging, because most artificial enzymes lack enzyme-like scale and configuration. Herein, for the first time, we leverage a defect engineering strategy to develop a simple yet efficient redox nanozyme by constructing enzyme-mimicking active centers and investigated its formation and catalysis mechanism thoroughly. Specifically, the partial Fe doping in MoO_x (donated as Fe-MoO_v) was demonstrated to activate structure reconstruction with abundant defect site generation, including Fe substitution and oxygen vacancy (OV) defects, which significantly enable the binding capacity and catalytic activity of Fe-MoO_v nanozymes in a synergetic fashion. More intriguingly, plenty of delocalized electrons appear due to Fe-facilitated band structure reconstruction, directly contributing to the remarkable surface plasmon resonance effect in the near-infrared (NIR) region. Under NIR-II laser irradiation, the designed Fe-MoO_v nanozymes are able to induce substantial disruption of redox and metabolism homeostasis in the tumor region via enzyme-mimicking cascade reactions, thus significantly augmenting therapeutic effects. This study that takes advantage of defect engineering offers new insights into developing high-efficiency redox nanozymes.

Self-Doping Surface Oxygen Vacancy-Induced Lattice Strains for Enhancing Visible Light-Driven Photocatalytic H2 Evolution over Black TiO2

The synergistic effect of surface oxygen vacancy with induced lattice strains on visible light-driven photocatalytic H₂ evolution over black TiO₂ was investigated. Experimental measurements and theoretical calculations on the lattice parameters of black TiO₂ show that surface oxygen vacancies induce internal lattice strain during two-step aluminothermic reduction, which regulates the band structure and optimizes the photoinduced charge behavior of black TiO₂. The hydrogen evolution rate of black TiO₂ with strain modification shows a 12-fold increase to 1.882 mmol/g· h (equal to 4.705 μmol/cm²·h) under visible light illumination. The metastable state caused by the surface oxygen vacancies leads to the formation of a high-energy surface, which enhances visible light absorption and improves the photoinduced charge separation efficiency. Furthermore, the internal lattice strain provides the driving force and channel for the directional movement of photoinduced electrons from the bulk to the high-energy surface for photocatalytic H₂ evolution. This strategy provides a new method for designing a high-performance photocatalyst for H₂ production.

Tunable NH4F-Assisted Synthesis of 3D Porous In2O3 Microcubes for Outstanding NO2 Gas-Sensing Performance: Fast Equilibrium at High Temperature and Resistant to Humidity at Room Temperature

NO₂ gas sensors based on metal oxides under wild conditions are highly demanded yet an incomplete surface reaction and humidity interference on the gas-sensing performance limit their applications. Herein, we report three-dimensional (3D) porous In₂O₃ microcubes via a simple hydrothermal strategy to produce outstanding NO₂ gas-sensing performance: fast equilibrium of the surface reaction at 150 °C and negligible humidity dependence on the NO₂ gas sensing at room temperature. The 3D porous In₂O₃ microcubes with high surface areas, suitable pore sizes, rich oxygen vacancies, and high conductivity are testified. The underlying structural transformation mechanism for 3D porous In₂O₃ is investigated in detail. The as-made 3D porous In₂O₃ microcubic gas sensors present excellent gas-sensing performance to 50 ppm NO₂ at 150 °C, including a high response value (2329), fast response/recovery time (10/9 s), a low detection limit (10 ppb), long-term stability (60 days), and strong selectivity. Furthermore, they exhibit relatively stable NO₂ gas response under humidity variation (20-80%). The NO₂ gas mechanism under the interference of water is also clarified.

Niobium and Titanium Carbides (MXenes) as Superior Photothermal Supports for CO2 Photocatalysis

The conversion of CO₂ into fuels and feedstock chemicals via photothermal catalysis holds promise for efficient solar energy utilization to tackle the global energy shortage and climate change. Despite recent advances, it is of emerging interest to explore promising materials with excellent photothermal properties to boost the performance of photothermal CO₂ catalysis. Here, we report the discovery of MXene materials as superior photothermal supports for metal nanoparticles. As a proof-of-concept study, we demonstrate that Nb₂C and Ti₃C₂, two typical MXene materials, can enhance the photothermal effect and thus boost the photothermal catalytic activity of Ni nanoparticles. A record CO₂ conversion rate of 8.50 mol·g_Ni^-1·h^-1 is achieved for Nb₂C-nanosheet-supported Ni nanoparticles under intense illumination. Our study bridges the gap between photothermal MXene materials and photothermal CO₂ catalysis toward more efficient solar-to-chemical energy conversions and stimulates the interest in MXene-supported metal nanoparticles for other heterogeneous catalytic reactions, particularly driven by sunlight.

Plasmonic photothermal catalysis for solar-to-fuel conversion: current status and prospects

Solar-to-fuel conversion through photocatalytic processes is regarded as promising technology with the potential to reduce reliance on dwindling reserves of fossil fuels and to support the sustainable development of our society. However, conventional semiconductor-based photocatalytic systems suffer from unsatisfactory reaction efficiencies due to limited light harvesting abilities. Recent pioneering work from several groups, including ours, has demonstrated that visible and infrared light can be utilized by plasmonic catalysts not only to induce local heating but also to generate energetic hot carriers for initiating surface catalytic reactions and/or modulating the reaction pathways, resulting in synergistically promoted solar-to-fuel conversion efficiencies. In this perspective, we focus primarily on plasmon-mediated catalysis for thermodynamically uphill reactions converting CO2 and/or H2O into value-added products. We first introduce two types of mechanism and their applications by which reactions on plasmonic nanostructures can be initiated: either by photo-induced hot carriers (plasmonic photocatalysis) or by light-excited phonons (photothermal catalysis). Then, we emphasize examples where the hot carriers and phonon modes act in concert to contribute to the reaction (plasmonic photothermal catalysis), with special attention given to the design concepts and reaction mechanisms of the catalysts. We discuss challenges and future opportunities relating to plasmonic photothermal processes, aiming to promote an understanding of underlying mechanisms and provide guidelines for the rational design and construction of plasmonic catalysts for highly efficient solar-to-fuel conversion.

Defect Engineering of Two-Dimensional Transition-Metal Dichalcogenides: Applications, Challenges, and Opportunities

Atomic defects, being the most prevalent zero-dimensional topological defects, are ubiquitous in a wide range of 2D transition-metal dichalcogenides (TMDs). They could be intrinsic, formed during the initial sample growth, or created by postprocessing. Despite the majority of TMDs being largely unaffected after losing chalcogen atoms in the outermost layer, a spectrum of properties, including optical, electrical, and chemical properties, can be significantly modulated, and potentially invoke applicable functionalities utilized in many applications. Hence, controlling chalcogen atomic defects provides an alternative avenue for engineering a wide range of physical and chemical properties of 2D TMDs. In this article, we review recent progress on the role of chalcogen atomic defects in engineering 2D TMDs, with a particular focus on device performance improvements. Various approaches for creating chalcogen atomic defects including nonstoichiometric synthesis and postgrowth treatment, together with their characterization and interpretation are systematically overviewed. The tailoring of optical, electrical, and magnetic properties, along with the device performance enhancement in electronic, optoelectronic, chemical sensing, biomedical, and catalytic activity are discussed in detail. Postformation dynamic evolution and repair of chalcogen atomic defects are also introduced. Finally, we offer our perspective on the challenges and opportunities in this field.

Enhanced CO2 Photocatalysis by Indium Oxide Hydroxide Supported on TiN@TiO2 Nanotubes

Herein is developed a ternary heterostructured catalyst, based on a periodic array of 1D TiN nanotubes, with a TiO₂ nanoparticulate intermediate layer and a In₂O_3-x(OH)_y nanoparticulate shell for improved performance in the photocatalytic reverse water gas shift reaction. It is demonstrated that the ordering of the three components in the heterostructure sensitively determine its activity in CO₂ photocatalysis. Specifically, TiN nanotubes not only provide a photothermal driving force for the photocatalytic reaction, owing to their strong optical absorption properties, but they also serve as a crucial scaffold for minimizing the required quantity of In₂O_3-x(OH)_y nanoparticles, leading to an enhanced CO production rate. Simultaneously, the TiO₂ nanoparticle layer supplies photogenerated electrons and holes that are transferred to active sites on In₂O_3-x(OH)_y nanoparticles and participate in the reactions occurring at the catalyst surface.

Photothermal catalysts for hydrogenation reactions

Hydrogenation reactions are an important process in today's chemical industry. Typically, hydrogenation reactions involve the removal of an unsaturated bond in olefins or other polyenes via thermal catalysis using hydrogen. As hydrogenation reactions are often carried out at temperatures up to several hundred degrees, they require significant energy input which typically comes from burning fossil fuels. In order to conserve fossil fuels and reduce CO₂ emissions, researchers are now developing photothermal catalysts for hydrogenation reactions, which harness concentrated sunlight to achieve the required reaction temperatures or introduce sunlight into thermal-driven reaction systems to reduce the reaction temperatures. Photothermal catalysts thus need to be able to efficiently absorb sunlight, whilst also being able to drive the desired hydrogenation reaction with high activity and selectivity. In this review, we summarize recent research aimed at the development of photothermal catalysts for CO₂/CO hydrogenation and alkene/alkyne/aromatic hydrogenation. Particular emphasis is placed on uncovering the reaction mechanisms at the molecular level, which in turn guides the rational design of photothermal catalysts with better performance.

Oxide-based composites: applications in thermo-photocatalysis

Recent progress on oxide-based thermo-photocatalytic composite systems. Role of plasmonic, defect-related, and thermal effects on the catalytic performance.

Dependence of the intrinsic phase structure of Bi2O3 catalysts on photocatalytic CO2 reduction

The combination of time-resolved transient photoluminescence with in-situ Fourier transform infrared spectroscopy has been conducted to investigate the intrinsic phase structure-dependent activity of Bi₂O₃ catalyst for CO₂ reduction.

Reverse water-gas shift reaction over Pt/MoOx/TiO2: reverse Mars–van Krevelen mechanism via redox of supported MoOx

Pt/MoO_x/TiO₂ shows excellent catalytic performance for the reverse water-gas shift reaction at 250 °C via reverse Mars–van Krevelen mechanism.