Surface Ru-H Bipyridine Complexes-Grafted TiO2 Nanohybrids for Efficient Photocatalytic CO2 Methanation

Reducing Dielectric Confinement Effect Enhances Carrier Separation in Two-Dimensional Hybrid Perovskite Photocatalysts

Two-dimensional organic-inorganic hybrid perovskites (OIHPs) with alternating structure of the organic and inorganic layers have a natural quantum well structure. The difference of dielectric constants between organic and inorganic layers in this structure results in the enhancement of dielectric confinement effect, which exhibits a large exciton binding energy and hinders the separation of electron-hole pairs. Herein, a strategy to reduce the dielectric confinement effect by narrowing the dielectric difference between organic amine molecule and [PbBr6]4- octahedron is put forward. The Ethanolamine (EOA) contains hydroxyl groups, resulting in the positive and negative charge centers of O and H non-overlapping, which generated a larger polarity and dielectric constant. The reduced dielectric constant produces a smaller exciton binding energy (71.03 meV) of (C2H7NO)2PbBr4 ((EOA)2PbBr4) than (C8H11N)2PbBr4 ((PEA)2PbBr4 (156.07 meV), and promotes the dissociation of electrons and holes. The increasing of lifetime of photogenerated carrier in (EOA)2PbBr4 are proved by femtosecond transient absorption spectra. Density functional theory (DFT) calculations have also indicated that the small energy shift of the total density of states (DOS) between the C/H/N and the Pb/Br in (EOA)2PbBr4 favors the separation of electrons and holes. In addition, this work demonstrates the application of (PEA)2PbBr4 and (EOA)2PbBr4 in the field of photocatalytic CO2 reduction.

Terpyridine Ni(II) Complex Grafted CdS Nanorods for Cooperative Selective Benzyl Alcohol Oxidation and Hydrogen Production

Efficient utilization of photogenerated charge carriers to realize photocatalytic solar fuel production and oxidative chemical synthesis is a challenging task. Herein, a conventional amidation reaction route is adopted to successfully construct a novel composite photocatalyst composed of a Ni(II)-terpyridine complex with carboxyl groups grafted on CdS nanorods (labeled as CdS@Ni(terpyC)2). Experimental results have unequivocally revealed that the as-fabricated composite catalyst exhibited a remarkable enhancement in photocatalytic activity for the dehydrogenation of benzyl alcohol under visible light, demonstrating superior hydrogen evolution efficiency and benzaldehyde selectivity, surpassing both pristine CdS and the blend of CdS and Ni(terpyC)2. The carrier dynamics study demonstrated that the Ni(terpyC)2 on the surface of CdS could quickly extract the photogenerated electrons of CdS, which reduced the carrier recombination efficiency, further improving the photocatalytic activity of the catalyst. This work illustrates the effect of surface active site engineering on photocatalysis and is expected to shed substantial inspiration on future surface modulation and design of semiconductor photocatalysts.

Unveiling the potential of MOF-based single-atom photocatalysts for the production of clean fuel and valuable chemical

Harnessing solar energy through photocatalysis has excellent potential for powering sustainable chemical production, supporting the United Nations' environmental goals. Single-atoms (SAs) dispersed on catalyst surfaces are gaining attention for their highly active and durable nature. Metal-organic frameworks (MOFs) can provide enough reactive sites to sustain selectivity and durability over time because of their tunable channels and functional groups. Owing to their organized structures, MOFs are ideal platforms for securing individual atoms and promoting solar-driven reactions. Few reviews have, however, reflected the possibility of combining MOFs and SAs to produce potent photocatalysts that may produce clean fuels and valuable chemicals. This review provides a general overview of methods for combining MOFs and SAs to generate photocatalysts. The challenges associated with these MOF-based single-atom systems are also critically examined. Their future development is discussed as continued refinement helps to more fully leverage their advantages for boosting photocatalytic performances - turning sunlight into chemicals in a manner that supports sustainable development. Insights gained here could illuminate pathways toward realizing the profound potential of MOF-based single-atom photocatalysts to empower production driven by renewable solar energy.

Unlocking Copper-Free Interfacial Asymmetric C-C Coupling for Ethylene Photosynthesis from CO2 and H2O

Solar-driven carbon dioxide (CO2) reduction into C2+ products such as ethylene represents an enticing route toward achieving carbon neutrality. However, due to sluggish electron transfer and intricate C-C coupling, it remains challenging to achieve highly efficient and selective ethylene production from CO2 and H2O beyond capitalizing on Cu-based catalysts. Herein, we report a judicious design to attain asymmetric C-C coupling through interfacial defect-rendered tandem catalytic centers within a sulfur-vacancy-rich MoSx/Fe2O3 photocatalyst sheet, enabling a robust CO2 photoreduction to ethylene without the need for copper, noble metals, and sacrificial agents. Specifically, interfacial S vacancies induce adjacent under-coordinated S atoms to form Fe-S bonds as a rapid electron-transfer pathway for yielding a Z-scheme band alignment. Moreover, these S vacancies further modulate the strong coupling interaction to generate a nitrogenase-analogous Mo-Fe heteronuclear unit and induce the upward shift of the d-band center. This bioinspired interface structure effectively suppresses electrostatic repulsion between neighboring *CO and *COH intermediates via d-p hybridization, ultimately facilitating an asymmetric C-C coupling to achieve a remarkable solar-to-chemical efficiency of 0.565% with a superior selectivity of 84.9% for ethylene production. Further strengthened by MoSx/WO3, our design unveils a promising platform for optimizing interfacial electron transfer and offers a new option for C2+ synthesis from CO2 and H2O using copper-free and noble metal-free catalysts.

Z-scheme heterojunction enhanced photocatalytic performance for CO2 reduction to CH4

Due to the high charge separation efficiency leading to high photocatalytic activity, there has been significant interest in enhancing the charge separation ability of photocatalysts by controlling the heterojunction structure. To investigate the effect of the heterojunction structure on the photocatalytic performance of composite catalysts and understand its corresponding mechanism, a Z-scheme ZnFe2O4/ZnO/CdS heterojunction was constructed using the ultrasound method and used for CO2 photoreduction. The Z-scheme heterojunction catalyst demonstrates elevated photocatalytic and charge separation efficiencies. Specifically, the conversion rate for the photocatalytic conversion of CO2 to CH4 reaches 105.9 μmol g-1 h-1, surpassing that of the majority of previously reported semiconductor photocatalysts like ZnFe2O4/CdS. This research offers a fresh perspective on the development of innovative heterojunction photocatalysts and broadens the utilization of ternary composite materials in CO2 photoreduction.

Organic-Inorganic Interfacial Dipole Induced by Energy Level Alignment for Efficient Photocatalytic Sterilization

Photocatalytic molecules are considered to be one of the most promising substitutions of antibiotics against multidrug-resistant bacterial infections. However, the strong excitonic effect greatly restricts their efficiency in antibacterial performance. Inspired by the interfacial dipole effect, a Ti3C2 MXene modified photocatalytic molecule (MTTTPyB) is designed and synthesized to enhance the yield of photogenerated carriers under light irradiation. The alignment of the energy level between Ti3C2 and MTTTPyB results in the formation of an interfacial dipole, which can provide an impetus for the separation of carriers. Under the role of a dipole electric field, these photogenerated electrons can rapidly migrate to the side of Ti3C2 for improving the separation efficiency of photogenerated electrons and holes. Thus, more electrons can be utilized to produce reactive oxygen species (ROS) under light irradiation. As a result, over 97.04% killing efficiency can be reached for Staphylococcus aureus (S. aureus) when the concentration of MTTTPyB/Ti3C2 was 50 ppm under 660 nm irradiation for 15 min. A microneedle (MN) patch made from MTTTPyB/Ti3C2 was used to treat the subcutaneous bacterial infection. This design of an organic-inorganic interface provides an effective method to minimize the excitonic effect of molecules, further expanding the platform of inorganic/organic hybrid materials for efficient phototherapy.

Hydrophobic TaOx Species Overlayer Tuning Light-Driven Methane Chlorination with Inorganic Chlorine

Halogenated methane serves as a universal platform molecule for building high-value chemicals. Utilizing sodium chloride solution for photocatalytic methane chlorination presents an environmentally friendly method for methane conversion. However, competing reactions in gas-solid-liquid systems leads to low efficiency and selectivity in photocatalytic methane chlorination. Here, an in situ method is employed to fabricate a hydrophobic layer of TaOx species on the surface of NaTaO3. Through in-situ XPS and XANES spectra analysis, it is determined that TaOx is a coordination unsaturated species. The TaOx species transforms the surface properties from the inherent hydrophilicity of NaTaO3 to the hydrophobicity of TaOx/NaTaO3, which enhances the accessibility of CH4 for adsorption and activation, and thus promotes the methane chlorination reaction within the gas-liquid-solid three-phase system. The optimized TaOx/NaTaO3 photocatalyst has a good durability for multiple cycles of methane chlorination reactions, yielding CH3Cl at a rate of 233 µmol g-1 h-1 with a selectivity of 83%. In contrast, pure NaTaO3 exhibits almost no activity toward CH3Cl formation, instead catalyzing the over-oxidation of CH4 into CO2. Notably, the activity of the optimized TaOx/NaTaO3 photocatalyst surpasses that of reported noble metal photocatalysts. This research offers an effective strategy for enhancing the selectivity of photocatalytic methane chlorination using inorganic chlorine ions.

Platinum Single-Atom Nests Boost Solar-Driven Photocatalytic Non-Oxidative Coupling of Methane to Ethane

This work introduces a new strategy of a single-atom nest catalyst, whereby several single atoms are positioned closely, aiming to achieve the dual benefits of high atom-utilization efficiency while avoiding the steric hindrance in the coupling reaction. As a proof of concept, Pt single-atom nests, where the adjacent Pt single atoms are approximately 4 Å apart, are precisely engineered on the TiO2 photocatalyst for photocatalytic non-oxidative coupling of methane. The Pt single-atom nest photocatalyst demonstrates remarkable activity, achieving a C2H6 yield and turnover frequency of 251.6 μmol gcat-1 h-1 and 20 h-1, respectively, representing a 3.2-fold improvement compared to the Pt single-atom photocatalyst. Density functional theory calculations reveal that the Pt single-atom nest can significantly decrease the energy barrier for the activation of both CH4 molecules in the coupling process.

Photosynthesis of CH3OH via oxygen-atom-grafting from CO2 to CH4 enabled by AuPd/GaN

The direct co-conversion of methane and carbon dioxide into valuable chemicals has been a longstanding scientific pursuit for carbon neutrality and combating climate change. Herein, we present a photo-driven chemical process that reforms these two major greenhouse gases together to generate green methanol and CO, two high-valued industrial chemicals. Isotopic labeling and control experiments indicate an oxygen-atom-graft occurs, wherein CO2 transfers one O into the C-H bond of CH4 via photo-activated interfacial catalysis with AuPd nanoparticles supported on GaN. The photoexcited AuPd/GaN interface effectively orchestrates the CH4 oxidation and the CO2 reduction producing 13.66 mmol g-1 of CH3OH yield over 10 h. This design provides a solid scientific basis for the photo-driven oxygen-atom-grafting process to be further extended to visible light region.

Single-cluster Functionalized TiO2 Nanotube Array for Boosting Water Oxidation and CO2 Photoreduction to CH3OH

Solar-driven CO2 reduction and water oxidation to liquid fuels represents a promising solution to alleviate energy crisis and climate issue, but it remains a great challenge for generating CH3OH and CH3CH2OH dominated by multi-electron transfer. Single-cluster catalysts with super electron acceptance, accurate molecular structure, customizable electronic structure and multiple adsorption sites, have led to greater potential in catalyzing various challenging reactions. However, accurately controlling the number and arrangement of clusters on functional supports still faces great challenge. Herein, we develop a facile electrosynthesis method to uniformly disperse Wells-Dawson- and Keggin-type polyoxometalates on TiO2 nanotube arrays, resulting in a series of single-cluster functionalized catalysts P2M18O62@TiO2 and PM12O40@TiO2 (M=Mo or W). The single polyoxometalate cluster can be distinctly identified and serves as electronic sponge to accept electrons from excited TiO2 for enhancing surface-hole concentration and promote water oxidation. Among these samples, P2Mo18O62@TiO2-1 exhibits the highest electron consumption rate of 1260 μmol g-1 for CO2-to-CH3OH conversion with H2O as the electron source, which is 11 times higher than that of isolated TiO2 nanotube arrays. This work supplied a simple synthesis method to realize the single-dispersion of molecular cluster to enrich surface-reaching holes on TiO2, thereby facilitating water oxidation and CO2 reduction.

Post-synthetic Metalation on the Ionic TiO2 Surface to Enhance Metal-CO2 Interaction During Photochemical CO2 Reduction

During the photochemical CO2 reduction reaction, CO2 adsorption on the catalyst's surface is a crucial step where the binding mode of the [metal-CO2] adduct directs the product selectivity and efficiency. Herein, an ionic TiO2 nanostructure stabilized by polyoxometalates (POM), ([POM]x@TiO2), is prepared and the sodium counter ions present on the surface to balance the POMs' charge are replaced with copper(II) ions, (Cux[POM]@TiO2). The microscopic and spectroscopic studies affirm the copper exchange without altering the TiO2 core and weak coordination of copper (II) ions to the POMs' surface. Band structure analysis suggests the photo-harvesting efficiency of the TiO2 core with the conduction band edge higher than the reduction potential of CuII/I and multi-electron CO2 reduction potentials. Photochemical CO2 reduction with Cux[POM]@TiO2 results in 30 μmol gcat. -1 CO (79 %) and 8 μmol gcat -1 of CH4 (21 %). Quasi-in-situ Raman study provides evidence in support of CO2 adsorption on the Cux[POM]@TiO2 surface. 13C and D2O labeling studies affirm the {Cu-[CO2]-} adduct formation. Despite the photo-harvesting ability of Nax[POM]@TiO2 itself, the poor CO2 adsorption ability of sodium ions highlights the crucial role of copper ion CO2 photo-reduction. Characterization of the {M-[η2-CO2]-} species via surface tuning validates the CO2 activation and photochemical reduction pathway proposed earlier.

Ni-Based Catalysts for CO2 Methanation: Exploring the Support Role in Structure-Activity Relationships

The catalytic hydrogenation of CO2 to methane is one of the highly researched areas for the production of chemical fuels. The activity of catalyst is largely affected by support type and metal-support interaction deriving from the special method during catalyst preparation. Hence, we employed a simple solvothermal technique to synthesize Ni-based catalysts with different supports and studied the support role (CeO2, Al2O3, ZrO2, and La2O3) on structure-activity relationships in CO2 methanation. It is found that catalyst morphology can be altered by only changing the support precursors during synthesis, and therefore their catalytic behaviours were significantly affected. The Ni/Al2O3 with a core-shell morphology prepared herein exhibited a higher activity than the catalyst prepared with a common wet impregnation method. To have a comprehensive understanding for structure-activity relationships, advanced characterization (e. g., synchrotron radiation-based XAS and photoionization mass spectrometry) and in-situ diffuse reflectance infrared Fourier transform spectroscopy experiments were conducted. This research opens an avenue to further delve into the role of support on morphologies that can greatly enhance catalytic activity during CO2 methanation.

Layered High-Entropy Metallic Glasses for Photothermal CO2 Methanation

High entropy alloys and metallic glasses, as two typical metastable nanomaterials, have attracted tremendous interest in energy conversion catalysis due to their high reactivity in nonequilibrium states. Herein, a novel nanomaterial, layered high entropy metallic glass (HEMG), in a higher energy state than low-entropy alloys and its crystalline counterpart due to both the disordered elemental and structural arrangements, is synthesized. Specifically, the MnNiZrRuCe HEMG exhibits highly enhanced photothermal catalytic activity and long-term stability. An unprecedented CO2 methanation rate of 489 mmol g-1 h-1 at 330 °C is achieved, which is, to the authors' knowledge, the highest photothermal CO2 methanation rate in flow reactors. The remarkable activity originates from the abundant free volume and high internal energy state of HEMG, which lead to the extraordinary heterolytic H2 dissociation capacity. The high-entropy effect also ensures the excellent stability of HEMG for up to 450 h. This work not only provides a new perspective on the catalytic mechanism of HEMG, but also sheds light on the great catalytic potential in future carbon-negative industry.

Catalyzing Artificial Photosynthesis with TiO2 Heterostructures and Hybrids: Emerging Trends in a Classical yet Contemporary Photocatalyst

Titanium dioxide (TiO2) stands out as a versatile transition-metal oxide with applications ranging from energy conversion/storage and environmental remediation to sensors and optoelectronics. While extensively researched for these emerging applications, TiO2 has also achieved commercial success in various fields including paints, inks, pharmaceuticals, food additives, and advanced medicine. Thanks to the tunability of their structural, morphological, optical, and electronic characteristics, TiO2 nanomaterials are among the most researched engineering materials. Besides these inherent advantages, the low cost, low toxicity, and biocompatibility of TiO2 nanomaterials position them as a sustainable choice of functional materials for energy conversion. Although TiO2 is a classical photocatalyst well-known for its structural stability and high surface activity, TiO2-based photocatalysis is still an active area of research particularly in the context of catalyzing artificial photosynthesis. This review provides a comprehensive overview of the latest developments and emerging trends in TiO2 heterostructures and hybrids for artificial photosynthesis. It begins by discussing the common synthesis methods for TiO2 nanomaterials, including hydrothermal synthesis and sol-gel synthesis. It then delves into TiO2 nanomaterials and their photocatalytic mechanisms, highlighting the key advancements that have been made in recent years. The strategies to enhance the photocatalytic efficiency of TiO2, including surface modification, doping modulation, heterojunction construction, and synergy of composite materials, with a specific emphasis on their applications in artificial photosynthesis, are discussed. TiO2-based heterostructures and hybrids present exciting opportunities for catalyzing solar fuel production, organic degradation, and CO2 reduction via artificial photosynthesis. This review offers an overview of the latest trends and advancements, while also highlighting the ongoing challenges and prospects for future developments in this classical yet rapidly evolving field.

Tailoring the catalytic sites by regulating photogenerated electron/hole pairs separation spatially for simultaneous selective oxidation of benzyl alcohol and hydrogen evolution

Photocatalytic selective oxidation of alcohols into aldehydes and H2 is a green strategy for obtaining both value-added chemicals and clean energy. Herein, a dual-purpose ZnIn2S4@CdS photocatalyst was designed and constructed for efficient catalyzing benzyl alcohol (BA) into benzaldehyde (BAD) with coupled H2 evolution. To address the deep-rooted problems of pure CdS, such as high recombination of photogenerated carriers and severe photo-corrosion, while also preserving its superiority in H2 production, ZnIn2S4 with a suitable band structure and adequate oxidizing capability was chosen to match CdS by constructing a coupled reaction. As designed, the photoexcited holes (electrons) in the CdS (ZnIn2S4) were spatially separated and transferred to the ZnIn2S4 (CdS) by electrostatic pull from the built-in electric field, leading to expected BAD production (12.1 mmol g-1 h-1) at the ZnIn2S4 site and H2 generation (12.2 mmol g-1 h-1) at the CdS site. This composite photocatalyst also exhibited high photostability due to the reasonable hole transfer from CdS to ZnIn2S4. The experimental results suggest that the photocatalytic transform of BA into BAD on ZnIn2S4@CdS is via a carbon-centered radical mechanism. This work may extend the design of advanced photocatalysts for more chemicals by replacing H2 evolution with N2 fixation or CO2 reduction in the coupled reactions.

Disclosing Support-Size-Dependent Effect on Ambient Light-Driven Photothermal CO2 Hydrogenation over Nickel/Titanium Dioxide

The size of support in heterogeneous catalysts can strongly affect the catalytic property but is rarely explored in light-driven catalysis. Herein, we demonstrate the size of TiO2 support governs the selectivity in photothermal CO2 hydrogenation by tuning the metal-support interactions (MSI). Small-size TiO2 loading nickel (Ni/TiO2 -25) with enhanced MSI promotes photo-induced electrons of TiO2 migrating to Ni nanoparticles, thus favoring the H2 cleavage and accelerating the CH4 formation (227.7 mmol g-1  h-1 ) under xenon light-induced temperature of 360 °C. Conversely, Ni/TiO2 -100 with large TiO2 prefers yielding CO (94.2 mmol g-1  h-1 ) due to weak MSI, inefficient charge separation, and inadequate supply of activated hydrogen. Under ambient solar irradiation, Ni/TiO2 -25 achieves the optimized CH4 rate (63.0 mmol g-1  h-1 ) with selectivity of 99.8 %, while Ni/TiO2 -100 exhibits the CO selectivity of 90.0 % with rate of 30.0 mmol g-1  h-1 . This work offers a novel approach to tailoring light-driven catalytic properties by support size effect.

Water-Mediated Selectivity Control of CH3 OH versus CO/CH4 in CO2 Photoreduction on Single-Atom Implanted Nanotube Arrays

Controllable methanol production in artificial photosynthesis is highly desirable due to its high energy density and ease of storage. Herein, single atom Fe is implanted into TiO2 /SrTiO3 (TSr) nanotube arrays by two-step anodization and Sr-induced crystallization. The resulting Fe-TSr with both single Fe reduction centers and dominant oxidation facets (001) contributes to efficient CO2 photoreduction and water oxidation for controlled production of CH3 OH and CO/CH4 . The methanol yield can reach to 154.20 µmol gcat -1 h-1 with 98.90% selectivity by immersing all the catalyst in pure water, and the yield of CO/CH4 is 147.48 µmol gcat -1 h-1 with >99.99% selectivity when the catalyst completely outside water. This CH3 OH yield is 50 and 3 times higher than that of TiO2 and TSr and stands among all the state-of-the-art catalysts. The facile gas-solid and gas-liquid-solid phase switch can selectively control CH3 OH production from ≈0% (above H2 O) to 98.90% (in H2 O) via slowly immersing the catalyst into water, where abundant •OH and H2 O around Fe sites play important role in selective CH3 OH production. This work highlights a new insight for water-mediated CO2 photoreduction to controllably produce CH3 OH.

In situ topotactic formation of an inorganic intergrowth bulk NiS/FeS@MgFe-LDH heterojunction to simulate CODH for the photocatalytic reduction of CO2

Enzyme-mimetic photocatalysis has been attracting much attention in bionic research, in which carbon monoxide dehydrogenase (CODH) is a suitable prototype for simulation to meet environmental and energy needs. In this study, we utilized the structural memory effect of layered double hydroxides (LDHs) to build inorganic intergrowth bulk heterojunctions (IIBHs) NiS/FeS@MgFe-LDHs via a pyrolytic topological vulcanization (PTV) method that imitated active C-clusters [Ni-4Fe-4S] in CODH. Enzyme mimicry was evaluated in terms of the microstructure and catalytic reaction site. The similarity between the microstructure of NiS/FeS@MgFe-LDHs and the CODH active group was demonstrated through XRD, XAFS and other characterisations. Subsequently, the obtained in situ irradiated X-ray photoelectron spectra and transient absorption spectra indicated the photogenerated electron transfer of the IIBH, wherein electrons finally accumulated in the conduction band of the NiS domain for the photocatalytic CO2 reduction reaction, which was similar to that of C-clusters [Ni-4Fe-4S] in which the Ni2+ ion was the reactive site. As a result, NiS/FeS@MgFe-LDHs achieved a high yield of CO at a rate of 2151.974 μmol g-1 h-1, which was 39.8 and 9.7 times more than that of NiMgFe-LDHs and NiMgFe-MMO, respectively. The study offers an innovative design route for developing IIBHs, providing novel opportunities for enzyme-mimetic photocatalysis.

Single-Site Ni-Grafted TiO2 with Diverse Coordination Environments for Visible-Light Hydrogen Production

Solar hydrogen production at a high efficiency holds the significant importance in the age of energy crisis, while the micro-environment manipulation of active sites on photocatalysts plays a profound role in enhancing the catalytic performance. In this work, a series of well-defined single-site Ni-grafted TiO2 photocatalysts with unique and specific coordination environments, 2,2'-bipyridine-Ni-O-TiO2 (T-Ni Bpy) and 2-Phenylpyridine-Ni-O-TiO2 (T-Ni Phpy), were constructed with the methods of surface organometallic chemistry combined with surface ligand exchange for visible-light-induced photocatalytic hydrogen evolution reaction (HER). A prominent rate of 33.82 μmol ⋅ g-1  ⋅ h-1 and a turnover frequency of 0.451 h-1 for Ni are achieved over the optimal catalyst T-Ni Bpy for HER, 260-fold higher than those of Ni-O-TiO2 . Fewer electrons trapped oxygen vacancies and a larger portion of long-lived photogenerated electrons (>3 ns, ~52.9 %), which were demonstrated by the electron paramagnetic resonance and femtosecond transient IR absorption, correspond to the photocatalytic HER activity over the T-Ni Bpy. The number of long-lived free electrons injected from the Ni photoabsorber to the conduction band of TiO2 is one of the determining factors for achieving the excellent HER activity.

Construction of Hexameric Ru-Substitution POMs to Improve Photocatalytic H2 Evolution

Converting solar energy into storable hydrogen energy by employing green photocatalytic technology offers a reliable alternative for meeting the energy crisis. The polyoxometalates are a promising candidate for hydrogen production photocatalysts because of their unique electronic and structural properties and controllable design at the molecular level. Introducing noble metals was proven to be an effective method to greatly enhance the photocatalytic efficiency of polyoxometalates. Herein, two unprecedented compounds of hexameric Ru-POMs, Na4H10[As2RuIV2W11O18(OH)4(H2O)6{AsW8RuIVO31(OH)Cl}2(B-β-AsW9O33)4]·93H2O (1) and Na2H19[AsRuIII2W11O20(OH)2(H2O)6(RuIIICl3)(B-β-AsW9O33)6]·90H2O (2), were successfully self-assembled. The H2 evolution rates of 1 and 2 under optimal conditions were 3578.75 and 3027.69 μmol h-1 g-1 with TONs of 255 and 205, respectively. The stability of 1 was demonstrated by a series of characterizations. Besides, a possible photocatalytic mechanism was proposed.

Electronic Interactions on Platinum/(Metal-Oxide)-Based Photocatalysts Boost Selective Photoreduction of CO2 to CH4

By supporting platinum (Pt) and cadmium sulfide (CdS) nanoparticles on indium oxide (In2 O3 ), we fabricated a CdS/Pt/In2 O3 photocatalyst. Selective photoreduction of carbon dioxide (CO2 ) to methane (CH4 ) was achieved on CdS/Pt/In2 O3 with electronic Pt-In2 O3 interactions, with CH4 selectivity reaching to 100 %, which is higher than that on CdS/Pt/In2 O3 without electronic Pt-In2 O3 interactions (71.7 %). Moreover, the enhancement effect of electronic Pt-(metal-oxide) interactions on selective photoreduction of CO2 to CH4 also occurs by using other common metal oxides, such as photocatalyst supports, including titanium oxide, gallium oxide, zinc oxide, and tungsten oxide. The electronic Pt-(metal-oxide) interactions separate photogenerated electron-hole pairs and convert CO2 into CO2 δ- , which can be easily hydrogenated into CH4 via a CO2 δ- →HCOO*→HCO*→CH*→CH4 path, thus boosting selective photoreduction of CO2 to CH4 . This offers a new way to achieve selective photoreduction of CO2 .

UV- and visible-light photocatalysis using Ni-Co bimetallic and monometallic hydrotalcite-like materials for enhanced CO2 methanation in sabatier reaction

The CO2 catalytic reduction activities of four different Co-modified Ni-based catalysts derived from hydrotalcite-like materials (HTCs) prepared by co-precipitation method were investigated under thermal and photocatalytic conditions. All catalysts were tested from 473 to 723 K at 10 bar (abs). The light intensity for photocatalytic reactions was 2.4 W cm-2. The samples were characterized to determine the effect of morphological and physicochemical properties of mono-bimetallic active phases on their methanation activity. The activity toward CO2 methanation followed the next order: Ni > Co-Ni > Co. For the monometallic Ni catalyst an increase of a 72% was achieved in the photo-catalytic activity under UV and vis light irradiation at temperatures lower by > 100 K than those in a conventional reaction. Co-modified Ni based hydrotalcite catalysts performed with stability and no deactivation for the 16 h studied under visible light for methanation at 523 K due to the presence of basic sites.

How organic switches grafting on TiO2 modifies the surface potentials: theoretical insights

Hybrid organic switch-inorganic semiconductor systems have important applications in both photo-responsive intelligent surfaces and microfluidic devices. In this context, herein, we performed first-principles calculations to investigate a series of organic switches of trans/cis-azobenzene fluoride and pristine/oxidized trimethoxysilane adsorbed on low-index anatase slabs. The trends in the surface-adsorbate interplay were examined in terms of the electronic structures and potential distributions. Consequently, it was found that the cis-azobenzene fluoride (oxidized trimethoxysilane)-terminated anatase surface attains a lower ionization potential than the trans-azobenzene fluoride (pristine trimethoxysilane)-terminated anatase surface due to its smaller induced (larger intrinsic) dipole moment, whose direction points inwards (outwards) from the substrate, which originates from the electron charge redistribution at the interface (polarity of attached hydroxyl groups). By combining the induced polar interaction analysis and the experimental measurements in the literature, we demonstrate that the ionization potential is an important predictor of the surface wetting properties of adsorbed systems. The anisotropic absorbance spectra of anatase grafted with azobenzene fluoride and trimethoxysilane are also related to the photoisomerization and oxidization process under UV irradiation, respectively.