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

Indium oxide with oxygen vacancies boosts O2 adsorption and activation for electrocatalytic H2O2 production

Oxygen reduction reaction via the two-electron pathway (2e- ORR) offers a sustainable opportunity for hydrogen peroxide (H2O2) production, but suffers from low selectivity. In this work, indium oxide with oxygen vacancies (In2O3-x) exhibits a H2O2 selectivity close to 98% at 0.6 V vs. RHE. Further, a Faradaic efficiency (FE) of around 95% at 0.4-0.6 V vs. RHE and a H2O2 productivity of 3.7 mol gcatalyst-1 h-1 are reached in a flow cell. In situ Raman spectra indicate that In2O3-x promotes the adsorption and activation of O2 and stabilizes oxygen intermediates. This work provides an insight into improving H2O2 selectivity for 2e- ORR catalysts.

Thermocatalytic Hydrogen Production from Water at Boiling Condition

Thermochemical water-splitting cycles are technically feasible for hydrogen production from water. However, the ultrahigh operation temperature and low efficiency seriously restrict their practical application. Herein, one-step and one-pot thermocatalytic water-splitting process is reported at water boiling condition catalyzed by single atomic Pt on defective In2O3. Water splitting into hydrogen is verified by D2O isotopic experiment, with an optimized hydrogen production rate of 36.4 mmol·h-1·g-1 as calculated on Pt active sites. It is revealed that three-centered Pt1In2 surrounding oxygen vacancy as catalytic ensembles promote the dissociation of the adsorbed water into H, which transfers to singlet atomic Pt sites for H2 production. Remaining OH groups on adjacent In sites from Pt1In2 ensembles undergoes O─O bonding, hyperoxide formation and diminishing via triethylamine oxidation, water re-adsorption for completing the catalytic cycle. Current work represents an isothermal and continuous thermocatalytic water splitting under mild condition, which can re-awaken the research interest to produce H2 from water using low-grade heat and competes with photocatalytic, electrolytic, and photoelectric reactions.

Mechanistic insight into near-infrared light-driven Cu2O/WO2 Ohmic contact photothermal catalysts for high-efficiency antibiotic wastewater purification

Near-infrared (NIR) light-induced photothermal effect is beneficial for accelerating catalytic processes; thus, it is imperative to develop novel photothermal catalysts for promoting practical application. Herein, we synthesized NIR-responsive Cu2O/WO2 Ohmic contact photothermal catalysts through a facile ethylene glycol-assisted liquid-phase reduction method. In this photothermal catalyst, a new-type NIR-responsive Cu2O semiconductor is integrated with an NIR-responsive WO2 semimetal component to form an Ohmic contact, which is more beneficial for simultaneously promoting photocharge separation and enhancing NIR light absorption for a high-efficiency photothermal effect. As expected, the Cu2O/WO2 composite displays higher NIR light-driven photothermal catalytic performance for tetracycline removal from wastewater. Various characterization methods and density functional theory calculations were performed to obtain in-depth mechanistic insights into the NIR light-driven Cu2O/WO2 Ohmic contact photothermal catalysts. Hopefully, this research could provide a useful guideline for researchers focusing on the photothermal engineering of new composite photocatalysts.

Autophagy-Inducing MoO3-x Nanowires Boost Photothermal-Triggered Cancer Immunotherapy

Autophagy could play suppressing role in cancer therapy by facilitating release of tumor antigens from dying cells and inducing immunogenic cell death (ICD). Therefore, discovery and rational design of more effective inducers of cytotoxic autophagy is expected to develop new strategies for finding innovative drugs for precise and successful cancer treatment. Herein, we develop MoO3-x nanowires (MoO3-x NWs) with high oxygen vacancy and strong photothermal responsivity to ablate tumors through hyperthermia, thus promote the induction of cytotoxic autophagy and severe ICD. As expected, the combination of MoO3-x NWs and photothermal therapy (PTT) effectively induces autophagy to promote the release of tumor antigens from the ablated cells, and induces the maturation and antigen presentation of dendritic cells (DCs), subsequently activates cytotoxic T lymphocytes (CTLs)-mediated adaptive immunity. Furthermore, the combination treatment of MoO3-x NWs with immune checkpoint blockade of PD-1 could promote the tumor-associated macrophages (TAMs) polarization into tumor-killing M1 macrophages, inhibit infiltration of Treg cells at tumor sites, and alleviate immunosuppression in the tumor microenvironment, finally intensify the anti-tumor activity in vivo. This study provides a strategy and preliminary elucidation of the mechanism of using MoO3-x nanowires with high oxygen vacancy to induce autophagy and thus enhance photothermal immunotherapy.

Role of Atomicity and Interface on InOx-TiO2 Composites: Thermo-Photo Valorization of CO2

The synthesis, physicochemical, and functional properties of composite solids resulting from the surface spread of oxidized indium species onto nanoplatelets of anatase were investigated. Both the size and the interaction between the indium- and titanium-containing components control the functional properties. In the reduction of CO2 to CO, the best samples have an indium content between ca. 2 and 5 mol % and showed an excess rate over the photo and thermo-alone processes above 33% and an energy efficiency of 1.3%. Subnanometric (monomeric and dimeric) indium species present relatively weak thermal catalytic response but strong thermo-photo promotion of the activity. A gradual change in functional properties was observed with the growth of the indium content of the solids, leading to a progressive increase of thermal activity but lower thermo-photo promotion. The study provides a well-defined structure-activity relationship rationalizing the dual thermo-photo properties of the catalysts and establishes a guide for the development of highly active and stable composite solids for the elimination and valorization of CO2.

Solar Energy-Driven Reverse Water Gas Shift Reaction: Photothermal Effect, Photoelectric Activation and Selectivity Regulation

Excessive carbon dioxide (CO2) emissions are one of the main causes of the greenhouse effect. Thermal catalytic reverse water gas shift (RWGS) reaction, which is a pre reaction for Fischer-Tropsch synthesis, is considered an effective way to convert CO2 and synthesize high value-added chemicals in industry. However, traditional thermal catalysis requires a large amount of fossil fuels to drive reactions, which cannot achieve the true goal of carbon neutrality. Photothermal catalysis, as a novel conversion pathway, can achieve efficient CO2 conversion while significantly improving solar energy utilization. This review provides a detailed introduction of CO2 and H2 adsorption/activation and reaction pathways in thermal catalysis, as well as the catalytic mechanisms of thermal and chemical effects in photothermal catalytic RWGS to supply readers valuable insights on the mechanism of photothermal catalytic RWGS reaction and provide a reference for better catalyst design.

Controlled Synthesis of Large-Area Oriented ZnO Nanoarrays

Large-area oriented ZnO nanoarrays (including nanowire, nanorod, and nanotube) on ITO glass substrates are synthesized via the simple hydrothermal, electrodeposition, and electrochemical etching approach. The morphology of ZnO nanoarrays is controlled by adjusting the reaction temperature, reaction time, and current density. The scanning and transmission electron microscopy (SEM and TEM) results indicate the successful preparation of large-area oriented ZnO nanoarrays with different types, and the energy-dispersive X-microanalysis spectrum (EDS) and X-ray diffraction (XRD) results confirm that the composition of the obtained nanoarrays is ZnO. More importantly, the as-prepared ZnO nanotube arrays are observed with about a 40% increase in ultraviolet absorption intensity compared to the ZnO nanowire/nanorod arrays, due to having larger specific surface areas. The as-prepared different types of ZnO nanoarrays have great potential for applications in low-cost and high-performance optoelectronic devices.

Phase Engineered CuxS-Ag2S with Photothermoelectric Activity for Enhanced Multienzyme Activity and Dynamic Therapy

The insufficient exposure sites and active site competition of multienzyme are the two main factors to hinder its therapeutic effect. Here, a phase-junction nanomaterial (amorphous-crystalline CuxS-Ag2S) is designed and prepared through a simple room temperature ion-exchange process. A small amount of Ag+ is added into Cu7S4 nanocrystals, which transforms Cu7S4 into amorphous phased CuxS and produces crystalline Ag2S simultaneously. In this structure, the overhanging bonds on the amorphous CuxS surface provide abundant active sites for optimizing the therapeutic activity. Meanwhile, the amorphous state enhances the photothermal effect through non-radiative relaxation, and due to its low thermal resistance, phase-junction CuxS-Ag2S forms a significant temperature gradient to unlock the optimized thermo-electrodynamic therapy. Furthermore, benefiting from the high asymmetry of the amorphous state, the material forms a spin-polarized state that can effectively inhibit electron-hole recombination. In this way, the thermoelectric effect can facilitate the enzyme-catalyzed cycle by providing electrons and holes, enabling an enhanced coupling of thermoelectric therapy with multienzyme activity, which induces excellent anti-tumor performance. More importantly, the catalytic process simulated by density-functional theory proves that Ag+ alleviates the burden on the Cu sites through favorable adsorption of O2 and prevents active site competition.

A Ni-O-Ag photothermal catalyst enables 103-m2 artificial photosynthesis with >17% solar-to-chemical energy conversion efficiency

The scalable artificial photosynthesis composed of photovoltaic electrolysis and photothermal catalysis is limited by inefficient photothermal CO2 hydrogenation under weak sunlight irradiation. Herein, NiO nanosheets supported with Ag single atoms [two-dimensional (2D) Ni1Ag0.02O1] are synthesized for photothermal CO2 hydrogenation to achieve 1065 mmol g-1 hour-1 of CO production rate under 1-sun irradiation. This performance is attributed to the coupling effect of Ag-O-Ni sites to enhance the hydrogenation of CO2 and weaken the CO adsorption, resulting in 1434 mmol g-1 hour-1 of CO yield at 300°C. Furthermore, we integrate the 2D Ni1Ag0.02O1-supported photothermal reverse water-gas shift reaction with commercial photovoltaic electrolytic water splitting to construct a 103-m2 scale artificial photosynthesis system (CO2 + H2O → CO + H2 + O2), which achieves more than 22 m3/day of green syngas with an adjustable H2/CO ratio (0.4-3) and a photochemical energy conversion efficiency of >17%. This research charts a promising course for designing practical, natural sunlight-driven artificial photosynthesis systems.

Non-Photochemical Origin of Selectivity Difference between Light and Dark Catalytic Conditions

The interest in introducing light into heterogeneous catalysis is driven not only by the urgent need of replacing fossil energy but also by the promise of controlling product selectivity by light. The product selectivity differences observed in recent studies between light and dark reactions are often attributed to photochemical effects. Here, we report the discovery of a non-photochemical origin of selectivity difference, at essentially the same CO2 conversion rate, between photothermal and thermal CO2 hydrogenation reactions over a Ru/TiO2-x catalyst. While the presence of the photochemical effect from ultraviolet light is confirmed, it merely enhances the catalytic activity. Systematic investigation reveals that the gradual formation of an adsorbate-mediated strong metal-support interaction under catalytic conditions is responsible for the variation in the catalytic selectivity. We demonstrate that differences in product selectivity under light/dark reactions do not necessarily originate from photochemical effects. Our study refines the basis for determining photochemical effects and highlights the importance of excluding non-photochemical effects in mechanistic studies of light-controlled product selectivity.

Efficient Thermal Management with Selective Metamaterial Absorber for Boosting Photothermal CO2 Hydrogenation under Sunlight

Photothermal catalytic CO2 hydrogenation is a prospective strategy to simultaneously reduce CO2 emission and generate value-added fuels. However, the demand of extremely intense light hinders its development in practical applications. Herein, this work reports the novel design of Ni-based selective metamaterial absorber and employs it as the photothermal catalyst for CO2 hydrogenation. The selective absorption property reduces the heat loss caused by radiation while possessing effectively solar absorption, thus substantially increasing local photothermal temperature. Notably, the enhancement of local electric field by plasmon resonance promotes the adsorption and activation of reactants. Moreover, benefiting from the ingenious morphology that Ni nanoparticles (NPs) are encapsulated by SiO2 matrix through co-sputtering, the greatly improved dispersion of Ni NPs enables enhancing the contact with reaction gas and preventing the agglomeration. Consequently, the catalyst exhibits an unprecedented CO2 conversion rate of 516.9 mmol gcat -1 h-1 under 0.8 W cm-2 irradiation, with near 90% CO selectivity and high stability. Significantly, this designed photothermal catalyst demonstrates the great potential in practical applications under sunlight. This work provides new sights for designing high-performance photothermal catalysts by thermal management.

Photothermal CO2 Catalysis toward the Synthesis of Solar Fuel: From Material and Reactor Engineering to Techno-Economic Analysis

Carbon dioxide (CO2), a member of greenhouse gases, contributes significantly to maintaining a tolerable environment for all living species. However, with the development of modern society and the utilization of fossil fuels, the concentration of atmospheric CO2 has increased to 400 ppm, resulting in a serious greenhouse effect. Thus, converting CO2 into valuable chemicals is highly desired, especially with renewable solar energy, which shows great potential with the manner of photothermal catalysis. In this review, recent advancements in photothermal CO2 conversion are discussed, including the design of catalysts, analysis of mechanisms, engineering of reactors, and the corresponding techno-economic analysis. A guideline for future investigation and the anthropogenic carbon cycle are provided.

A Comprehensive Review on the Boosted Effects of Anion Vacancy in the Heterogeneous Photocatalytic Degradation, Part II: Focus on Oxygen Vacancy

Environmental problems, including the increasingly polluted water and the energy crisis, have led to a need to propose novel strategies/methodologies to contribute to sustainable progress and enhance human well-being. For these goals, heterogeneous semiconducting-based photocatalysis is introduced as a green, eco-friendly, cost-effective, and effective strategy. The introduction of anion vacancies in semiconductors has been well-known as an effective strategy for considerably enhancing the photocatalytic activity of such photocatalytic systems, giving them the advantages of promoting light harvesting, facilitating photogenerated electron-hole pair separation, optimizing the electronic structure, and enhancing the yield of reactive radicals. This Review will introduce the effects of anion vacancy-dominated photodegradation systems. Then, their mechanism will illustrate how an anion vacancy changes the photodegradation pathway to enhance the degradation efficiency toward pollutants and the overall photocatalytic performance. Specifically, the vacancy defect types and the methods of tailoring vacancies will be briefly illustrated, and this part of the Review will focus on the oxygen vacancy (OV) and its recent advances. The challenges and development issues for engineered vacancy defects in photocatalysts will also be discussed for practical applications and to provide a promising research direction. Finally, some prospects for this emerging field will be proposed and suggested. All permission numbers for adopted figures from the literature are summarized in a separate file for the Editor.

Multifunctional In-MOF and Its S-Scheme Heterojunction toward Pollutant Decontamination via Fluorescence Detection, Physical Adsorption, and Photocatalytic REDOX

A novel doubly interpenetrated indium-organic framework of 1 has been assembled by In3+ ions and highly conjugated biquinoline carboxylate-based bitopic connectors (H2L). The isolated 1 exhibits an anionic framework possessing channel-type apertures repleted with exposed quinoline N atoms and carboxyl O atoms. Owing to the unique architecture, 1 displays a durable photoluminescence effect and fluorescence quenching sensing toward CrO42-, Cr2O72-, and Cu2+ ions with reliable selectivity and anti-interference properties, fairly high detection sensitivity, and rather low detection limits. Ligand-to-ligand charge transition (LLCT) was identified as the essential cause of luminescence by modeling the ground state and excited states of 1 using DFT and TD-DFT. In addition, the negatively charged framework has the ability to rapidly capture single cationic MB, BR14, or BY24 and their mixture, including the talent to trap MB from the (MB + MO) system with high selectivity. Moreover, intrinsic light absorption capacity and band structure feature endow 1 with effective photocatalytic decomposition ability toward reactive dyes RR2 and RB13 under ultraviolet light. Notably, after further polishing the band structure state of 1 by constructing the S-scheme heterojunction of In2S3/1, highly efficient photocatalytic detoxification of Cr(VI) and degradation of reactive dyes have been fully achieved under visible light. This finding may open a new avenue for designing novel multifunctional MOF-based platforms to address some intractable environmental issues, i.e., detection of heavy metal ions, physical capture of pony-sized dyes, and photochemical decontamination of ultrastubborn reactive dyes and highly toxic Cr(VI) ions from water.

Construction of Photothermo-Electro Coupling Field Based on Surface Modification of Hydrogenated TiO2 Nanotube Array Photoanode and Its Improved Photoelectrochemical Water Splitting

Solar water splitting has gained increasing attention in converting solar energy into green hydrogen energy. However, the construction of a photothermo-electro coupling field by harnessing light-induced heat and its enhancement on solar water splitting were seldom studied. Herein, we developed a full-spectrum responsive photoanode by depositing CdxZn1-xS onto the surface of hydrogenated TiO2 nanotube array (H-TNA), followed by modification with Ni2P. The resulting ternary photoanode exhibits a photocurrent density of 4.99 mA·cm-2 at 1.23 V vs. RHE with photoinduced heating, which is 11.9-fold higher than that of pristine TNA, with an optimal ABPE of 2.47%. The characterization results demonstrate that the ternary photoanode possesses superior full-spectrum absorption and efficient photogenerated carrier separation driven by the interface electric fields. Additionally, Ni2P reduces the hole injection barrier and increases surface active sites, accelerating the consumption of holes accumulating on the relatively unstable CdxZn1-xS to simultaneously improve the activity and stability of water splitting. Moreover, temperature-dependent measurements reveal that H-TNA and Ni2P significantly motivate the photothermal conversion to construct a photothermo-electro coupling field, optimizing photoelectric conversion and charge carrier-induced surface reactions. This work contributes to understanding the synergistic effect of the photothermo-electro coupling field on the photoelectrochemical water splitting.

Sulfur defect induced Cd0.3Zn0.7S in-situ anchoring on metal organic framework for enhanced photothermal catalytic CO2 reduction to prepare proportionally adjustable syngas

The rapid recombination of interfacial charges is considered to be the main obstacle limiting the photocatalytic CO2 reduction. Thus, it is a challenge to research an accurate and stable charge transfer control strategy. MIL-53 (Al)-S/Cd0.3Zn0.7S (MAS/CZS-0.3) photocatalysts with chemically bonded interfaces were constructed by in-situ electrostatic assembly of sulfur defect Cd0.3Zn0.7S (CZS-0.3) on the surface of MIL-53 (Al) (MAW), which enhanced interfacial coupling and accelerated electron transfer efficiency. An adjustable proportion of syngas (H2/CO) was prepared by photothermal catalytic CO2 reduction at micro-interface. and the optimal yield of CO (66.10 μmol∙g-1∙h-1) and H2 (71.0 μmol∙g-1∙h-1) was realized by the MAS/CZS-0.3 photocatalyst. The improved activity was due to the photogenerated electrons migrated from CZS-0.3 to the adsorption active sites of MAS, which strengthened the adsorption and activation of CO2 on MAS. The photothermal catalytic CO2 reduction to CO follows the pathway of CO2→*COOH → CO and CO2→*HCO3-→CO. This work provided a reference for the research, characterization, and application of in-situ anchoring of metal organic frameworks in photothermal catalytic CO2 reduction, and provided a green path for the supply of Syngas in industry.

A comprehensive review on the boosted effects of anion vacancy in the heterogeneous photocatalytic degradation, part I: Focus on sulfur, nitrogen, carbon, and halogen vacancies

The greenest environmental remediation way is the photocatalytic degradation of organic pollutants. However, limited photocatalytic applications are due to poor sunlight absorption and photogenerated charge carriers' recombination. These limitations can be overcome by introducing anion vacancy (AV) (O, S, N, C, and Halogen) defects in semiconductors that enhance light harvesting, facilitate charge separation, modulate electronic structure, and produce reactive radicals. In continuing part A of this review, in this part, we summarized the recent AVs' research, including S, N, C, and halogen vacancies on the boosted photocatalytic features of semiconductor materials, like metal oxides/sulfides, oxyhalides, and nitrides in detail. Also, we outline the recently developed AV designs for the photocatalytic degradation of organic pollutants. The AV creating and analysis methods and the recent photocatalytic applications and mechanisms of AV-mediated photocatalysts are reviewed. AV engineering photocatalysts' challenges and development prospects are illustrated to get a promising research direction.

Defect Engineering of WO3 by Rapid Flame Reduction for Efficient Photoelectrochemical Conversion of Methane into Liquid Oxygenates

Photoelectrochemical (PEC) conversion is a promising way to use methane (CH4) as a chemical building block without harsh conditions. However, the PEC conversion of CH4 to value-added chemicals remains challenging due to the thermodynamically favorable overoxidation of CH4. Here, we report WO3 nanotube (NT) photoelectrocatalysts for PEC CH4 conversion with high liquid product selectivity through defect engineering. By tuning the flame reduction treatment, we carefully controlled the oxygen vacancies of WO3 NTs. The optimally reduced WO3 NTs suppressed overoxidation of CH4 showing a high total C1 liquid selectivity of 69.4% and a production rate of 0.174 μmol cm-2 h-1. Scanning electrochemical microscopy revealed that oxygen vacancies can restrain the production of hydroxyl radicals, which, in excess, could further oxidize C1 intermediates to CO2. Additionally, band diagram analysis and computational studies elucidated that oxygen vacancies thermodynamically suppress overoxidation. This work introduces a strategy for understanding and controlling the selectivity of photoelectrocatalysts for direct conversion of CH4 to liquids.

Wettability Engineering of Solar Methanol Synthesis

Engineering the wettability of surfaces with hydrophobic organics has myriad applications in heterogeneous catalysis and the large-scale chemical industry; however, the mechanisms behind may surpass the proverbial hydrophobic kinetic benefits. Herein, the well-studied In2O3 methanol synthesis photocatalyst has been used as an archetype platform for a hydrophobic treatment to enhance its performance. With this strategy, the modified samples facilitated the tuning of a wide range of methanol production rates and selectivity, which were optimized at 1436 μmol gcat-1 h-1 and 61%, respectively. Based on in situ DRIFTS and temperature-programmed desorption-mass spectrometry, the surface-decorated alkylsilane coating on In2O3 not only kinetically enhanced the methanol synthesis by repelling the produced polar molecules but also donated surface active H to facilitate the subsequent hydrogenation reaction. Such a wettability design strategy seems to have universal applicability, judged by its success with other CO2 hydrogenation catalysts, including Fe2O3, CeO2, ZrO2, and Co3O4. Based on the discovered kinetic and mechanistic benefits, the enhanced hydrogenation ability enabled by hydrophobic alkyl groups unleashes the potential of the surface organic chemistry modification strategy for other important catalytic hydrogenation reactions.

Rational Design of N-Doped Carbon-Coated Cobalt Nanoparticles for Highly Efficient and Durable Photothermal CO2 Conversion

Photothermal CO2 hydrogenation to high-value-added chemicals and fuels is an appealing approach to alleviate energy and environmental concerns. However, it still relies on the development of earth-abundant, efficient, and durable catalysts. Here, the design of N-doped carbon-coated Co nanoparticles (NPs), as a photothermal catalyst, synthesized through a two-step pyrolysis of Co-based ZIF-67 precursor, is reported. Consequently, the catalyst exhibits remarkable activity and stability for photothermal CO2 hydrogenation to CO with a 0.75 mol gcat -1 h-1 CO production rate under the full spectrum of light illumination. The high activity and durability of these Co NPs are mainly attributed to the synergy of the attuned size of Co NPs, the thickness of carbon layers, and the N doping species. Impressively, the experimental characterizations and theoretical simulations show that such a simple N-doped carbon coating strategy can effectively facilitate the desorption of generated CO and activation of reactants due to the strong photothermal effect. This work provides a simple and efficient route for the preparation of highly active and durable nonprecious metal catalysts for promising photothermal catalytic reactions.

Reconfigurable Manipulation of Oxygen Content on Metal Oxide Surfaces and Applications to Gas Sensing

Oxygen vacancies and adsorbed oxygen species on metal oxide surfaces play important roles in various fields. However, existing methods for manipulating surface oxygen require severe settings and are ineffective for repetitive manipulation. We present a method to manipulate the amount of surface oxygen by modifying the oxygen adsorption energy by electrically controlling the electron concentration of the metal oxide. The surface oxygen control ability of the method is verified using first-principles calculations based on density functional theory (DFT), X-ray photoelectron spectroscopy (XPS), and electrical resistance analysis. The presented method is implemented by fabricating oxide thin film transistors with embedded microheaters. The method can reconfigure the oxygen vacancies on the In2O3, SnO2, and IGZO surfaces so that specific chemisorption dominates. The method can selectively increase oxidizing (e.g., NO and NO) and reducing gas (e.g., H2S, NH3, and CO) reactions by electrically controlling the metal oxide surface to be oxygen vacancy-rich or adsorbed oxygen species-rich. The proposed method is applied to gas sensors and overcomes their existing limitations. The method makes the sensor insensitive to one gas (e.g., H2S) in mixed-gas environments (e.g., NO2+H2S) and provides a linear response (R2 = 0.998) to the target gas (e.g., NO2) concentration within 3 s. We believe that the proposed method is applicable to applications utilizing metal oxide surfaces.

Synergistic Modulation between Non-thermal and Thermal Effects in Photothermal Catalysis based on Modified In2O3

To promote the solar-energy cascade utilization, it is necessary to increase the thermal effect of irradiation in the catalytic reactions, while simultaneously augmenting the non-thermal effect, so as to fulfill photothermal coupling. Herein, the non-thermal and thermal effect of light radiation on the surface of In2O3-based catalysts are explored and enhanced by the modification of transition metals Fe and Cu. Optical characterizations combined with water-splitting experiments show that Fe doping greatly broadens the radiation response range and enhances the absorption intensity of semiconductors' intrinsic portion, and Cu doping facilitates the absorption of visible-infrared light. The concurrent incorporation of Fe and Cu offers synergistic benefits, resulting in improved radiation response range, carrier separation and migration, as well as higher photothermal temperature upon photoexcitation. Collectively, these advantages comprehensively enhance the photothermal synergistic water-splitting reactivity. The characterizations under variable temperature conditions have demonstrated that the reaction temperature exerts a significant influence on the process of radiation absorption and conversion, ultimately impacting the non-thermal effect. The results of DFT calculations have revealed that the increasing temperature directly impacts the chemical reaction by reducing the energy barrier associated with the rate-determining step. These findings shine new light on the fundamental mechanisms underlying non-thermal and thermal effect, while also imparting significant insights for photo-thermal-coupled catalyst designing.

Selective conversion of CO2 to isobutane-enriched C4 alkanes over InZrOx-Beta composite catalyst

Direct conversion of CO₂ to a single specific hydrocarbon with high selectivity is extremely attractive but very challenging. Herein, by employing an InZrO_x-Beta composite catalyst in the CO₂ hydrogenation, a high selectivity of 53.4% to butane is achieved in hydrocarbons (CO free) under 315 °C and 3.0 MPa, at a CO₂ conversion of 20.4%. Various characterizations and DFT calculation reveal that the generation of methanol-related intermediates by CO₂ hydrogenation is closely related to the surface oxygen vacancies of InZrO_x, which can be tuned through modulating the preparation methods. In contrast, the three-dimensional 12-ring channels of H-Beta conduces to forming higher methylbenzenes and methylnaphthalenes containing isopropyl side-chain, which favors the transformation of methanol-related intermediates to butane through alkyl side-chain elimination and subsequent methylation and hydrogenation. Moreover, the catalytic stability of InZrO_x-Beta in the CO₂ hydrogenation is considerably improved by a surface silica protection strategy which can effectively inhibit the indium migration.

Synergistic effect of double Schottky potential well and oxygen vacancy for enhanced plasmonic photocatalytic U(VI) reduction

Plasmonic photocatalysis is an effective strategy to solve radioactive uranium hazards in wastewater. A plasmonic photocatalyst Bi/Bi₂O_3-x@COFs was synthesized by in-situ growth of covalent organic frameworks (COFs) on Bi/Bi₂O_3-x surface for the U(VI) adsorption and plasmonic photoreduction in rare earth tailings wastewater. The presence of oxygen vacancy in Bi/Bi₂O_3-x and Schottky potential well formed by Bi and Bi₂O_3-x interface increased the number of free electrons, which induced localized surface plasmon resonance (LSPR) and enhanced the light absorption performance of composites. In addition, oxygen vacancy improved the Fermi level of Bi/Bi₂O_3-x, leading to another potential well between Bi₂O_3-x and COFs interface. The electron transport direction was reversed, thus increasing the electron density of COFs layer. COFs was an N-type semiconductor with specific binding U(VI) groups and suitable band structure, which could be used as an active reaction site. Bi/Bi₂O_3-x@COFs had 1411.5 mg g^-1 removal capacity and high separation coefficient for U(VI) due to the synergistic action of photogenerated electrons and hot electrons. Moreover, the removal rate of uranium from rare earth tailings wastewater by regenerated Bi/Bi₂O_3-x@COFs was over 93.9%. The scheme of introducing LSPR and Schottky potential well provides another way to improve the photocatalytic effect.

Ni nanoparticles supported on Al2O3 + La2O3 yolk-shell catalyst for photo-assisted thermal decomposition of methane

Catalytic methane decomposition (CMD) has emerged as an appealing technology for large-scale production of H₂ and carbon nanostructures from natural gas. As the CMD process is mildly endothermic, the application of concentrated renewable energy sources such as solar energy under a low-temperature regime could potentially represent a promising approach towards CMD process operation. Herein, Ni/Al₂O₃-La₂O₃ yolk-shell catalysts are fabricated using a straightforward single-step hydrothermal approach and tested for their performance in photothermal CMD. We show that the morphology of the resulting materials, dispersion and reducibility of Ni nanoparticles, and nature of metal-support interactions can be tuned by addition of varying amounts of La. Notably, the addition of an optimal amount of La (Ni/Al-20La) improved the H₂ yield and catalyst stability relative to the base Ni/Al₂O₃ material, while also favoring base growth of carbon nanofibers. Additionally, we show for the first time a photothermal effect in CMD, whereby the introduction of 3 suns light irradiation at a constant bulk temperature of 500 °C reversibly increased the H₂ yield of catalyst by about 1.2 times relative to the rate in the dark, accompanied by a decrease in apparent activation energy from 41.6 kJ mol^-1 to 32.5 kJ mol^-1. The light irradiation further suppressed undesirable CO co-production at low temperatures. Our work reveals photothermal catalysis as a promising route for CMD while providing an insightful understanding of the roles of modifier in enriching methane activation sites on Al₂O₃-based catalysts.

Selective CO2 Photoreduction to Acetate at Asymmetric Ternary Bridging Sites

Photoreduction of CO₂ is a promising strategy to synthesize value-added fuels or chemicals and realize carbon neutralization. Noncopper catalysts are seldom reported to generate C₂ products, and the selectivity over these catalysts is low. Here, we design rich-interface, heterostructured In₂O₃/InP (r-In₂O₃/InP) for highly competitive photocatalytic CO₂-to-CH₃COOH conversion with a productivity of 96.7 μmol g^-1 and selectivity > 96% along with water oxidation to O₂ in pure water (no sacrificial agent) under visible light irradiation. The hard X-ray absorption near-edge structure (XANES) shows that the formation of r-In₂O₃/InP with the isogenesis cation adjusts the coordination environment via interface engineering and forms O-In-P polarized sites at the interface. In situ FT-IR and Raman spectra identify the key intermediates of OCCO* for acetate production with high selectivity. Density functional theory (DFT) calculations reveal that r-In₂O₃/InP with rich O-In-P polarized sites promotes C-C coupling to form C₂ products because of the imbalanced adsorption energies of two carbon atoms. This work reports an interesting indium-based photocatalyst for selective CO₂ photoreduction to acetate under strict solution and irradiation conditions and provides significant insights into fabricating interfacial polarization sites to promote the process.

Enhanced Interfacial Electron Transfer by Asymmetric Cu-Ov -In Sites on In2 O3 for Efficient Peroxymonosulfate Activation

Enhancing the peroxymonosulfate (PMS) activation efficiency to generate more radicals is vital to promote the Fenton-like reaction activity, however, how to promote the PMS adsorption and accelerate the interfacial electron transfer to boost its activation kinetics remains a great challenge. Herein, we prepared Cu-doped defect-rich In₂ O₃ (Cu-In₂ O₃ /O_v ) catalysts containing asymmetric Cu-O_v -In sites for PMS activation in water purification. The intrinsic catalytic activity is that the side-on adsorption configuration of the O-O bond (Cu-O-O-In) at the Cu-O_v -In sites significantly stretches the O-O bond length. Meanwhile, the Cu-O_v -In sites increase the electron density near the Fermi energy level, promoting more and faster electron transfer to the O-O bond for generating more SO₄ ⋅^- and ⋅OH. The degradation rate constant of tetracycline achieved by Cu-In₂ O₃ /O_v is 31.8 times faster than In₂ O₃ /O_v , and it shows the possibility of membrane reactor for practical wastewater treatment.

Continuously Flow Photothermal Catalysis Efficiently CO2 Reduction Over S-Scheme 2D/0D Bi5 O7 I-OVs/Cd0.5 Zn0.5 S Heterojunction with Strong Interfacial Electric Field

Using CO₂ , water, and sunlight to produce solar fuel is a very attractive process, which can synchronously reduce carbon and convert solar energy into hydrocarbons. However, photocatalytic CO₂ reduction is often limited by the low selectivity of reduction products and poor photocatalytic activity. In this study, S-scheme Bi₅ O₇ I-OVs/Cd_0.5 Zn_0.5 S (Bi₅ O₇ I-OVs/CZS-0.5) heterojunction with strong interfacial electric field (IEF) is prepared by in situ growth method. The performance of reduction CO₂ to CO is studied by continuous flow photothermal catalytic (PTC) CO₂ reduction platform. 12.5% Bi₅ O₇ I-OVs/CZS-0.5 shows excellent CO yield of 58.6 µmol g^-1  h^-1 and selectivity of 98.4%, which are 35.1 times than that of CZS-0.5 under visible light. The charge transfer path of the S-scheme through theoretical calculation (DFT), in situ irradiation Kelvin probe force microscope (ISI-KPFM) and in situ irradiation X-ray photoelectron spectroscopy (ISI-XPS) analysis, is verified. The study can provide useful guidance and reference for improving activity by oxygen vacancy induced strong IEF and the development of a continuous flow PTC CO₂ reduction system.

Etching dopant elements to construct active-site-rich Mo2C for the hydrogen evolution reaction

We propose a strategy to etch dopants to construct Mo₂C with more unsaturated coordination of Mo atoms and lattice distortion for enhanced catalytic activity. It is more effective than doping and etching pure Mo₂C and provides a novel strategy for the preparation of catalysts with high catalytic activity.

Nanostructured Materials for Photothermal Carbon Dioxide Hydrogenation: Regulating Solar Utilization and Catalytic Performance

Converting carbon dioxide (CO₂) into value-added fuels or chemicals through photothermal catalytic CO₂ hydrogenation is a promising approach to alleviate the energy shortage and global warming. Understanding the nanostructured material strategies in the photothermal catalytic CO₂ hydrogenation process is vital for designing photothermal devices and catalysts and maximizing the photothermal CO₂ hydrogenation performance. In this Perspective, we first describe several essential nanomaterial design concepts to enhance sunlight absorption and utilization in photothermal CO₂ hydrogenation. Subsequently, we review the latest progress in photothermal CO₂ hydrogenation into C₁ (e.g., CO, CH₄, and CH₃OH) and multicarbon hydrocarbon (C₂₊) products. Finally, the relevant challenges and opportunities in this exciting research realm are discussed. This perspective provides a comprehensive understanding for the light-heat synergy over nanomaterials and instruction for rational photothermal catalyst design for CO₂ utilization.

Two-dimensional nanomaterials: synthesis and applications in photothermal catalysis

Photothermal catalysis, as one of the emerging technologies with synergistic effects of photochemistry and thermochemistry, is highly attractive in the fields of environment and energy. Two-dimensional (2D) nanomaterials have received extensive attention toward photothermal catalysis because of their ultrathin layer structures, superior physical and optical properties, and high surface areas. These merits are beneficial for shortening the transfer distance of charge carriers, improving the efficiency of solar to thermal, and providing a great opportunity for the development of photothermal chemistry. In this review, we have summarized the state-of-art advances in various 2D nanomaterials with emphasis on the driving force and relevant mechanism of photothermal catalysis, including the involved three types, namely, localized surface plasmonic resonance (LSPR), nonradiative relaxation, and thermal vibrations of molecules. Moreover, the synthesis strategies of 2D materials and their photothermal applications in carbon dioxide (CO₂) conversion, hydrogen (H₂) production, volatile organic compounds (VOCs) degradation, and water (H₂O) purification have been discussed in detail. Ultimately, the existing challenges and prospects of future development in the field are proposed. It is believed that this review will afford a great reference for the exploration of the high-efficiency 2D nanomaterials and their structure-activity relationship.

Synergistic Interactions of Neighboring Platinum and Iron Atoms Enhance Reverse Water-Gas Shift Reaction Performance

The limitations of conventional strategies in finely controlling the composition and structure demand new promotional effects for upgrading the reverse water-gas shift (RWGS) catalysts for enhanced fuel production. We report the design and synthesis of a hetero-dual-site catalyst for boosting RWGS performance by controllably loading Fe atoms at the neighboring Pt atom on the surface of commercial CeO₂. The Fe-Pt/CeO₂ exhibits a remarkably high catalytic performance (TOF_Pt: 43,519 h^-1) for CO₂ to CO conversion with ∼100% CO selectivity at a relatively low temperature of 350 °C. Furthermore, the catalyst retains over 80% activity after 200 h of continuous operation. The experimental and computational investigations reveal a "two-way synergistic effect", where Fe atoms can not only serve as promotors to alter the charge density of Pt atoms but also be activated by the excess active hydrogen species generated by Pt atoms, enhancing catalytic activity and stability.

Identification of the Active Sites on Metallic MoO2-x Nano-Sea-Urchin for Atmospheric CO2 Photoreduction Under UV, Visible, and Near-Infrared Light Illumination

We report an oxygen vacancy (V_o )-rich metallic MoO_2-x nano-sea-urchin with partially occupied band, which exhibits super CO₂ (even directly from the air) photoreduction performance under UV, visible and near-infrared (NIR) light illumination. The V_o -rich MoO_2-x nano-sea-urchin displays a CH₄ evolution rate of 12.2 and 5.8 μmol g_catalyst ^-1  h^-1 under full spectrum and NIR light illumination in concentrated CO₂ , which is ca. 7- and 10-fold higher than the V_o -poor MoO_2-x , respectively. More interestingly, the as-developed V_o -rich MoO_2-x nano-sea-urchin can even reduce CO₂ directly from the air with a CO evolution rate of 6.5 μmol g_catalyst ^-1  h^-1 under NIR light illumination. Experiments together with theoretical calculations demonstrate that the oxygen vacancy in MoO_2-x can facilitate CO₂ adsorption/activation to generate *COOH as well as the subsequent protonation of *CO towards the formation of CH₄ because of the formation of a highly stable Mo-C-O-Mo intermediate.

Two-dimensional heterostructures for photocatalytic CO2 reduction

The photocatalysis conversion of CO₂ into fuels has become an encouraging method to address climate and energy issues as a long-term solution. Single material suffers poor yield due to low light energy utilization and high recombination rate of photoinduced electron-hole pairs. It is an efficient approach to construct heterojunction through two or three materials to improve the photocatalytic performance. Recently, 2D-based heterojunction is getting popular for outstanding properties, such as special light collecting structure to enhance light harvest, intimate interface to facilitate charge transfer and separation, and large specific surface area to provide abundant reactive sites. Recently, some new 2D-based heterostructures materials (both structure and composition) have been developed with excellent performance. 2D materials exert structural and functional advantages in these fine composite photocatalysts. In this review, the literatures about the photocatalytic conversion of CO₂ are mainly summarized based on overall structure, interface type and material type of 2D-based heterojunction, with special attention given to the preparation, characterization, structural advantages and reaction mechanism of novel 2D-based heterojunction. This work is in hope of offering a basis for designing improved composite photocatalyst for CO₂ photoreduction.

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

In this work, a CdS/BiVO₄ 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/BiVO₄ to avoid photocorrosion while retaining the strong reducing capacity of CdS and the oxidizing capacity of BiVO₄. Experimental results such as radical quenching experiments and electron spin resonance show that U(VI) is rapidly oxidized by photoholes/^•OH to insoluble UO₂(OH)₂ after being reduced to U(IV) by photoelectrons/^•O₂⁻, 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.

Nanoscale hetero-interfaces for electrocatalytic and photocatalytic water splitting

As green and sustainable methods to produce hydrogen energy, photocatalytic and electrochemical water splitting have been widely studied. In order to find efficient photocatalysts and electrocatalysts, materials with various composition, size, and surface/interface are investigated. In recent years, constructing suitable nanoscale hetero-interfaces can not only overcome the disadvantages of the single-phase material, but also possibly provide new functionalities. In this review, we systematically introduce the fundamental understanding and experimental progress in nanoscale hetero-interface engineering to design and fabricate photocatalytic and electrocatalytic materials for water splitting. The basic principles of photo-/electro-catalytic water splitting and the fundamentals of nanoscale hetero-interfaces are briefly introduced. The intrinsic behaviors of nanoscale hetero-interfaces on electrocatalysts and photocatalysts are summarized, which are the electronic structure modulation, space charge separation, charge/electron/mass transfer, support effect, defect effect, and synergistic effect. By highlighting the main characteristics of hetero-interfaces, the main roles of hetero-interfaces for electrocatalytic and photocatalytic water splitting are discussed, including excellent electronic structure, efficient charge separation, lower reaction energy barriers, faster charge/electron/mass transfer, more active sites, higher conductivity, and higher stability on hetero-interfaces. Following above analysis, the developments of electrocatalysts and photocatalysts with hetero-structures are systematically reviewed.

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.