Conversion Of H2O Research Articles

Ultraschnelle oberflächenspezifische Spektroskopie von Wasser an einem photoangeregten TiO2‐Modell‐Photokatalysator zur Wasserspaltung

AbstractEin kritischer Schritt bei der photokatalytischen Wasserdissoziation ist die lochvermittelte Oxidationsreaktion. Einblicke auf molekularer Ebene in den Mechanismus dieser komplexen Reaktion unter realistischen Bedingungen mit hoher zeitlicher Auflösung sind äußerst wünschenswert. Wir verwenden Femtosekunden zeitaufgelöste, oberflächenspezifische Summenfrequenzspektroskopie, um die photoinduzierte Reaktion direkt an der Grenzfläche des Photokatalysators TiO2 in Kontakt mit flüssigem Wasser bei Raumtemperatur zu untersuchen. Dank der inhärenten Oberflächenspezifität der spektroskopischen Methode können wir spezifisch die Reaktion von den Grenzflächenwassermolekülen direkt an der Grenzfläche auf Zeitskalen auf denen die Reaktion abläuft verfolgen. Nach der Erzeugung von Löchern an der Oberfläche des Katalysators, sofort nach der Photoanregung mit UV‐Licht, erfolgt die Wasserdissoziation auf einer Zeitskala von unter 20 ps. Der Reaktionsmechanismus ist bei pH 3 und 11 ähnlich. In beiden Fällen beobachten wir die Umwandlung von H2O in Ti−OH‐Gruppen und die Deprotonierung bereits vorhandener Ti−OH‐Gruppen. Diese Studie bietet einzigartige experimentelle Einblicke in die frühen Schritte der photoinduzierten Dissoziationsprozesse an der Photokatalysator‐Wasser Grenzfläche, die für die Entwicklung verbesserter Photokatalysatoren relevant sind.

Accelerated Photocatalytic Carbon Dioxide Reduction and Water Oxidation under Spatial Synergy.

Photocatalytic conversion of CO2 and H2 O into fuels and oxygen is a highly promising solution for carbon-neutral recycling. Traditionally, researchers have studied CO2 reduction and H2 O oxidation separately, overlooking potential synergistic interplay between these processes. This study introduces an innovative approach, spatial synergy, which encourages synergistic progress by bringing the two half-reactions into atomic proximity. To facilitate this, we developed a defective ZnIn2 S4 -supported single-atom Cu catalyst (Cu-SA/D-ZIS), which demonstrates remarkable catalytic performance with CO2 reduction rates of 112.5 μmol g-1 h-1 and water oxidation rates of 52.3 μmol g-1 h-1 , exhibiting a six-fold enhancement over D-ZIS. The structural characterization results indicated that the trapping effect of vacancy associates on single-atom copper led to the formation of an unsaturated coordination structure, Cu-S3 , consequently giving rise to the CuZn 'VS ⋅⋅VZn " defect complexes. FT-IR studies coupled with theoretical calculations reveal the spatially synergistic CO2 reduction and water oxidation on CuZn 'VS ⋅⋅VZn ", where the breakage of O-H in water oxidation is synchronized with the formation of *COOH, significantly lowering the energy barrier. Notably, this study introduces and, for the first time, substantiates the spatial synergy effect in CO2 reduction and H2 O oxidation through a combination of experimental and theoretical analyses, providing a fresh insight in optimizing photocatalytic system.

Accelerated Photocatalytic Carbon Dioxide Reduction and Water Oxidation under Spatial Synergy

AbstractPhotocatalytic conversion of CO2 and H2O into fuels and oxygen is a highly promising solution for carbon‐neutral recycling. Traditionally, researchers have studied CO2 reduction and H2O oxidation separately, overlooking potential synergistic interplay between these processes. This study introduces an innovative approach, spatial synergy, which encourages synergistic progress by bringing the two half‐reactions into atomic proximity. To facilitate this, we developed a defective ZnIn2S4‐supported single‐atom Cu catalyst (Cu−SA/D−ZIS), which demonstrates remarkable catalytic performance with CO2 reduction rates of 112.5 μmol g−1 h−1 and water oxidation rates of 52.3 μmol g−1 h−1, exhibiting a six‐fold enhancement over D−ZIS. The structural characterization results indicated that the trapping effect of vacancy associates on single‐atom copper led to the formation of an unsaturated coordination structure, Cu‐S3, consequently giving rise to the CuZn′VS⋅⋅VZn“ defect complexes. FT‐IR studies coupled with theoretical calculations reveal the spatially synergistic CO2 reduction and water oxidation on CuZn′VS⋅⋅VZn”, where the breakage of O−H in water oxidation is synchronized with the formation of *COOH, significantly lowering the energy barrier. Notably, this study introduces and, for the first time, substantiates the spatial synergy effect in CO2 reduction and H2O oxidation through a combination of experimental and theoretical analyses, providing a fresh insight in optimizing photocatalytic system.

Direct conversion of CO and H2O to hydrocarbons at atmospheric pressure using a TiO2−x/Ni photothermal catalyst

Direct conversion of CO and H2O to hydrocarbons at atmospheric pressure using a TiO2−x/Ni photothermal catalyst

Determination of local pH in CO2 electroreduction.

The electrocatalytic conversion of CO2 and H2O into fuels and valuable chemicals has gained significant interest as a prospective method for the storage of renewable energy and the utilization of captured CO2. In the process of electroreduction of CO2, pH near the surface of the electrocatalysts plays an important role in the catalytic selectivity and activity. However, to elucidate the local pH effect on the fundamental reaction mechanism and modify the catalytic CO2 reduction performance, the localized pH determination method is highly desirable. In this minireview, we present the recent advances in the strategies of the local pH probe for CO2 electrolysis in both H-type cell reactors and GDE-type flow electrolyzers, followed with a better understanding of the local reaction environment in CO2 reduction. Additionally, pertinent advantages and drawbacks of the different localized pH probe techniques are discussed, and perspectives on future research efforts are also provided in this minireview.

A g-C3N4/rGO/Cs3Bi2Br9 mediated Z-scheme heterojunction for enhanced photocatalytic CO2 reduction.

Photocatalytic CO2 reduction plays a crucial role in advancing solar fuels, and enhancing the efficiency of the chosen photocatalysts is essential for sustainable energy production. This study demonstrates advancements in the performance of g-C3N4 as a photocatalyst achieved through surface modifications such as exfoliation to increase surface area and surface oxidation for improved charge separation. We also introduce reduced graphene oxide (rGO) in various ratios to both bulk and exfoliated g-C3N4, which effectively mitigates charge recombination and establishes an optimal ratio for enhanced efficiency. g-C3N4/rGO serves to fabricate a hybrid organic/inorganic heterojunction with Cs3Bi2Br9, resulting in a g-C3N4/rGO/Cs3Bi2Br9 composite. This leads to a remarkable increase in photocatalytic conversion of CO2 and H2O to CO, H2 and CH4 at rates of 54.3 (±2.0) μmole- g-1 h-1, surpassing that of pure Cs3Bi2Br9 (11.2 ± 0.4 μmole- g-1 h-1) and bulk g-C3N4 (5.5 ± 0.5 μmole- g-1 h-1). The experimentally determined energy diagram indicates that rGO acts as a solid redox mediator between g-C3N4 and Cs3Bi2Br9 in a Z-scheme heterojunction configuration, ensuring that the semiconductor (Cs3Bi2Br9) with the shallowest conduction band drives the reduction and the one with the deepest valence band (g-C3N4) drives the oxidation. The successful formation of this high-performance heterojunction underscores the potential of the developed composite as a photocatalyst for CO2 reduction, offering promising prospects for advancing the field of solar fuels and achieving sustainable energy goals.

Nanoconfined tandem three-phase photocatalysis for highly selective CO2 reduction to ethanol.

The conversion of CO2 and H2O into ethanol with high selectivity via photocatalysis is greatly desired for effective CO2 resource utilization. However, the sluggish and challenging C-C coupling hinders this goal, with the behavior of *CO holding the key. Here, a nanoconfined and tandem three-phase reaction system is established to simultaneously enhance the *CO concentration and interaction time, achieving an outstanding ethanol selectively of 94.15%. This system utilizes a tandem catalyst comprising an Ag core and a hydrophobic Cu2O shell. The hydrophobic Cu2O shell acts as a CO2 reservoir, effectively overcoming the CO2 mass-transfer limitation, while the Ag core facilitates the conversion of CO2 to CO. Subsequently, CO undergoes continuous reduction within the nanoconfined mesoporous channels of Cu2O. The synergy of enhanced mass transfer, nanoconfinement, and tandem reaction leads to elevated *CO concentrations and prolonged interaction time within the Cu2O shell, significantly reducing the energy barrier for *CO-*CO coupling compared to the formation of *CHO from *CO, as determined by density functional theory calculations. Consequently, C-C coupling preferentially occurs over *CHO formation, producing excellent ethanol selectivity. These findings provide valuable insights into the efficient production of C2+ compounds.

A dual-functional metalloporphyrin-fluorenone covalent organic framework for solar hydrogen and oxygen production

Developing efficient dual-functional photocatalysts for the solar-driven conversion of H2O into H2 and O2 is a challenging yet promising approach to achieve carbon-free fuel production.

Oxygen Electrode Surface Constructing for Reversible Protonic Ceramic Electrochemical Cells

Reversible protonic ceramic electrochemical cells (R-PCECs) have great potential for energy conversion and storage at low-intermediate temperatures (400-700oC), which could enable the conversion of H2O into H2 in electrolysis (EL) mode, and inversely the production of electricity in fuel cell (FC) mode. However, the sluggish kinetics of oxygen reduction/evolution reaction (ORR/OER) at reduced temperatures, as well as undesired surface segregation and structural deterioration, have impeded the development of R-PCECs devices. In this presentation, we introduce a double-perovskite type oxygen electrode that has been optimized for enhanced reaction activity and surface stability using an efficient fluorite catalyst coating. Specifically, the oxygen electrode, PrBaCo2O5+δ (PBC), has been infiltrated with an active and durable shell, Pr0.1Ce0.9O2+δ (PCO). The obtained results show that PCO-PBC possess elevated oxygen vacancy concentration which would improve the surface exchange process, facilitate ion diffusion, and provide multiple active reaction sites, while simultaneously preventing Ba segregation during operation. Therefore, the fuel-electrode-supported single cell with a PCO-PBC oxygen electrode achieves high performance and a negligible degradation in EL and FC dual modes for 25 cycles and 100 h at 650 oC with 3vol.% H2O.

Hydroxyl-Bonded Ru on Metallic TiN Surface Catalyzing CO2 Reduction with H2O by Infrared Light.

Synchronized conversion of CO2 and H2O into hydrocarbons and oxygen via infrared-ignited photocatalysis remains a challenge. Herein, the hydroxyl-coordinated single-site Ru is anchored precisely on the metallic TiN surface by a NaBH4/NaOH reforming method to construct an infrared-responsive HO-Ru/TiN photocatalyst. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (ac-HAADF-STEM) and X-ray absorption spectroscopy (XAS) confirm the atomic distribution of the Ru species. XAS and density functional theory (DFT) calculations unveil the formation of surface HO-RuN5-Ti Lewis pair sites, which achieves efficient CO2 polarization/activation via dual coordination with the C and O atoms of CO2 on HO-Ru/TiN. Also, implanting the Ru species on the TiN surface powerfully boosts the separation and transfer of photoinduced charges. Under infrared irradiation, the HO-Ru/TiN catalyst shows a superior CO2-to-CO transformation activity coupled with H2O oxidation to release O2, and the CO2 reduction rate can further be promoted by about 3-fold under simulated sunlight. With the key reaction intermediates determined by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and predicted by DFT simulations, a possible photoredox mechanism of the CO2 reduction system is proposed.

Preparation and performance evaluation of low temperature SOEC using lithium compounds as electrodes

Previous studies have found that in ceramic fuel cells using Ni0·8Co0·15Al0·05LiO2 (NCAL) as the electrode, lithium compounds such as LiOH generated by reduction of NCAL anode by H2 diffuse into oxide electrolyte membranes such as Gd0.1Ce0·9O2 (GDC), and the “GDC-lithium compounds” composite electrolyte formed online is an excellent proton conductor. In this paper, the low-temperature electrolysis performance of proton conductor type solid oxide electrolysis cell (P-SOEC) with GDC as electrolyte and NCAL as electrode for direct electrochemical conversion of H2O into H2 was investigated. It is found that at operation temperature of 550 °C, the current density of the SOEC prepared in this paper can reach 2.263 A cm−2 at 1.6 V. The composite electrolyte in the electrolysis cell reaches an ionic conductivity of 0.572 S cm−1 in the SOEC mode. The excellent hydrogen production performance proves that this new type of electrolysis cell with lithium compounds as electrodes is a promising and potential proton conductive low-temperature SOEC.

Enhanced Z-scheme ZnS/NH2−MIL-125(Ti) photocatalysts with biomass-derived carbon quantum dots for CO2 reduction

The conversion of CO2 and H2O into hydrocarbon fuels using solar energy represents a promising approach to artificial photosynthesis. However, the rapid recombination of photogenerated carriers presents a significant obstacle to the development of this technology. In this study, we extracted carbon quantum dots (CQDs) from waste biomass sludge and utilized them as electron transfer mediators between ZnS and NH2−MIL-125(Ti) for CO2 photoreduction. Comparative analysis with single-phase and binary composites revealed that the ZnS/CQDs/NH2−MIL-125(Ti) composites exhibited heightened photocatalytic activity and improved photostability. Electrochemical and optical investigations further elucidated that the incorporation of CQDs enhanced the charge separation efficiency and visible light responsiveness of the composites. The yields of CH3OH and CH3CH2OH achieved were 501.57 µmol/g and 564.70 µmol/g, respectively, following 3 h of visible light irradiation. This study presents a novel reference for utilizing biomass to facilitate the conversion of CO2 and H2O into valuable chemicals.

Controlled crystal facet of tungsten trioxide photoanode to improve on-demand hydrogen peroxide production for in-situ tetracycline degradation

Advanced oxidation processes utilizing hydrogen peroxide (H2O2) are widely employed for the treatment of organic pollutions. However, the conventional anthraquinone method for H2O2 synthesis is unsuitable for this application owing to its hazardous and costly nature. Alternative approaches involve a photoelectrochemical method. Herein, tungsten trioxide (WO3) photoanode has been used for the conversion of H2O into H2O2 through oxidation reaction from a PEC system, simultaneously utilizing in-situ generated hydroxyl (OH•) radicals for tetracycline degradation. By manipulating the ratio of crystal facets between (020) and (200) of the WO3 photoanode, a significant improvement in H2O2 production has been achieved by increasing the proportion of (020) facet. The production rate of WO3 photoanode enriched with the (020) facet is approximately 1.9 times higher than that enriched with (200) facet. This enhanced H2O2 production performance can be attributed to the improved formation of OH• radicals and the accelerated desorption of H2O2 on the (020) facet. Simultaneously, the in-situ generated OH• radicals are applied for tetracycline degradation. Under illumination of sunlight stimulator for 180 min, the optimal photoanode achieves a degradation rate of 86.7% for tetracycline. Furthermore, the resulting chemicals have been analyzed, revealing that C8H10O and C7H8O were formed as the primary products. Notably, these products exhibit significantly lower toxicity compared to tetracycline. This study presents a promising approach for the rational design of WO3 based photoanodes for oxidation reaction, including not only H2O2 production but also the efficient degradation of organic pollutants.

Boosted C-C coupling with Cu-Ag alloy sub-nanoclusters for CO2-to-C2H4 photosynthesis.

The selective photocatalytic conversion of CO2 and H2O to high value-added C2H4 remains a great challenge, mainly attributed to the difficulties in C-C coupling of reaction intermediates and desorption of C2H4* intermediates from the catalyst surface. These two key issues can be simultaneously overcome by alloying Ag with Cu which gives enhanced activity to both reactions. Herein, we developed a facile stepwise photodeposition strategy to load Cu-Ag alloy sub-nanoclusters (ASNCs) on TiO2 for CO2 photoreduction to produce C2H4. The optimized catalyst exhibits a record-high C2H4 formation rate (1110.6 ± 82.5 μmol g-1 h-1) with selectivity of 49.1 ± 1.9%, which is an order-of-magnitude enhancement relative to current work for C2H4 photosynthesis. The in situ FT-IR spectra combined with DFT calculations reveal the synergistic effect of Cu and Ag in Cu-Ag ASNCs, which enable an excellent C-C coupling capability like Ag and promoted C2H4* desorption property like Cu, thus advancing the selective and efficient production of C2H4. The present work provides a deeper understanding on cluster chemistry and C-C coupling mechanism for CO2 reduction on ASNCs and develops a feasible strategy for photoreduction CO2 to C2 fuels or industrial feedstocks.

Power transition cycles of reversible solid oxide cells and its impacts on microgrids

Currently, reversible solid oxide cells (rSOC) are the only devices that allows a bidirectional conversion of H2O and H2, being able to operate as fuel cell and as electrolyzer. Thanks to the high-temperature operation, rSOC present a higher efficiency and additionally, provide a feasible solution for long-term energy storage in electrical systems. Experimental testing of rSOC have been mainly focused on cells characterization, thermal or degradation analysis, but the study of transition cycles has not been widely studied. The transitions between the operation as a solid oxide fuel cell (SOFC) and as a solid oxide electrolysis cell (SOEC) might have a significant impact on the rest of the electrical system in which the rSOC is integrated. This article analyzes experimentally the power responses of a rSOC stack, during each operating mode (SOEC-SOFC) and during transition between both modes. The results suggest that transition cycles can be achieved in less than 8 min and the total transition from SOEC rated power to SOFC rated power in less than 10 min, having a significant impact on microgrid operations, especially in islanded mode. The obtained results indicate that the most suitable role for rSOC in a microgrid is as grid-following. The grid-forming role is only possible if the rSOC operates along with a fast-response power source.

Tracking Heterogeneous Interface Charge Reverse Separation in SrTiO3/NiO/NiS Nanofibers with In Situ Irradiation XPS

AbstractPhotocatalytic conversion of H2O and CO2 into solar fuels is considered to be a green and renewable technology while photocatalytic performance is hampered by the severe recombination of photogenerated electron–hole pairs. Drawing inspiration from the concepts of the electrons transfer layer (ETL) and the holes transfer layer (HTL) in perovskite solar cells, a multicomponent photocatalyst SrTiO3/NiO/NiS that incorporates p–n heterojunction and Schottky junction is constructed for converting solar energy into easily storable solar fuels. The NiS and NiO play the roles analogy to the ETL and the HTL which accomplishes the reverse migration of electrons and holes, accordingly, SrTiO3/NiO/NiS exhibits a noticeable enhancement in photocatalytic performance. However, the lack of direct observation of charge transfer pathways in complex multicomponent photocatalysts makes it challenging to thoroughly investigate their catalytic mechanisms. Herein, the in situ irradiation X‐ray photoelectron spectroscopy (ISI–XPS) is employed to track photogenerated charges migration pathways between microscopic heterogeneous interfaces, thereby providing a comprehensive elucidation of the catalytic mechanism and heterojunction formation process by integrating the photoelectrochemical tests. This study not only serves as compelling evidence for the capability of ISI–XPS in directly and accurately tracking charge transfer pathways but also as an intriguing highlight within the catalyst design strategy.

Direct Synthesis of Formamide from CO2 and H2O with Nickel-Iron Nitride Heterostructures under Mild Hydrothermal Conditions.

Formamide can serve as a key building block for the synthesis of organic molecules relevant to premetabolic processes. Natural pathways for its synthesis from CO2 under early earth conditions are lacking. Here, we report the thermocatalytic conversion of CO2 and H2O to formate and formamide over Ni-Fe nitride heterostructures in the absence of synthetic H2 and N2 under mild hydrothermal conditions. While water molecules act as both a solvent and hydrogen source, metal nitrides serve as nitrogen sources to produce formamide in the temperature range of 25-100 °C under 5-50 bar. Longer reaction times promote the C-C bond coupling and formation of acetate and acetamide as additional products. Besides liquid products, methane and ethane are also produced as gas-phase products. Postreaction characterization of Ni-Fe nitride particles reveals structural alteration and provides insights into the potential reaction mechanism. The findings indicate that gaseous CO2 can serve as a carbon source for the formation of C-N bonds in formamide and acetamide over the Ni-Fe nitride heterostructure under simulated hydrothermal vent conditions.

Tröger's base derived 3D-porous aromatic frameworks with efficient exciton dissociation and well-defined reactive site for near-unity selectivity of CO2 photo-conversion

The overall photocatalytic conversion of CO2 and H2O to fuel and O2 is challenging. In this study, a series of three-dimensional Tröger's base-derived porous aromatic frameworks (3D-X-TB-PAFs (X = TEPE, TEPM, SPF)) featuring designated reaction sites and unique charge transfer properties were developed. The incorporation of V-shaped Tröger's base (TB) units and aromatic alkynes imparts the polymers with permanent porosity, additional photon scattering cross-sections, and enhanced CO2 adsorption/activation capabilities. Density functional theory calculations and optoelectronic measurements revealed the formation of intramolecular built-in polarization and electron-trap sites induced by TB, which modulated charge separation and customized reaction sites in collaboration with 3D networks. In addition, product allocation during the photoreduction of CO2 was regulated by the photooxidation of H2O. Among the as-prepared 3D-PAFs, the most efficient electron transport channel was demonstrated by the TEPE-TB-PAF with fully conjugated TEPE-T. In the absence of cocatalysts and sacrificial agents, TEPE-TB-PAF exhibits a competitive CO formation rate (194.50 μmol g−1 h−1) with near-unity selectivity (99.74%). Significantly, the low energy barrier for CO desorption and the high energy barrier for *CHO formation contribute to the high efficiency of TEPE-TB-PAF, as demonstrated by computational exploration and in situ diffuse reflectance infrared Fourier transform spectra. This work offers efficient building blocks for the synthesis of multifunctional organic photocatalysts and groundbreaking insights into the simultaneous enhancement of photocatalytic reactivity and selectivity.

Coupling the full solar spectrum with a two-step thermo-electrolytic cycle for efficient solar hydrogen production

H2O splitting via redox cycles of metal oxides provides a promising path for solar hydrogen production. For various redox cycles with hybrid driving forces, the introduction of spectral splitting is expected to reduce the exergy degradation at the initial step and realize the cascade utilization of the full solar spectrum. A thermodynamic model coupling the full solar spectrum with a two-step thermo-electrolytic cycle was established in this work, based on which the cycling performance was theoretically examined. Solar spectral splitting at an adjustable cut-off wavelength was employed to allow for a flexible allocation of the solar spectrum to meet the thermal and electrical energy demands of the cycle. Solar-to-H2 efficiency can be significantly improved by the introduction of spectral splitting. It can be as high as 35.4% for the redox cycle performed with CeO2-δ, and the optimal reduction temperature can be lowered from 1323 K to 1123 K. Isothermal cycles have an efficiency advantage over non-isothermal cycles due to the elimination of the energy cost for oxygen carrier heating. However, they are also accompanied with lower H2O conversion rates and higher oxygen carrier demands, for which a compromise may be needed from a practical view. Oxygen carriers with lower oxygen affinity were shown to have a higher efficiency potential than pure ceria (CeO2-δ). However, as the reduction enthalpy drops close to or even lower than the enthalpy of direct H2O splitting, the efficiency decreases fast due to insufficient driving force for the oxidation reaction.

Electronic and energy level structural engineering of graphitic carbon nitride nanotubes with B and S co-doping for photocatalytic hydrogen evolution

The ideal photocatalyst used for photocatalytic water splitting requires strong light absorption, fast charge separation/transfer ability and abundant active sites. Heteroatom doping offers a promising and rational approach to optimize the photocatalytic activity. However, achieving high photocatalytic performance remains challenging if just relying on single-element doping. Herein, Boron (B) and sulfur (S) dopants are simultaneously introduced into graphitic carbon nitride (g-C3N4) nanotubes by supramolecular self­assembly strategy. The developed B and S co-doped g-C3N4 nanotubes (B,S-TCN) exhibited an outstanding photocatalytic performance in the conversion of H2O into H2 (9.321 mmol g−1h−1), and the corresponding external quantum efficiency (EQE) reached 5.3% under the irradiation of λ = 420 nm. It is well evidenced by the closely combined experimental and (density functional theory) DFT calculations: (1) the introduction of B dopants can facilitate H2O adsorption and drive interatomic electron transfer, leading to efficient water splitting reaction. (2) S dopants can stretch the VB position to promote the oxidation ability of g-C3N4, which can accelerate the consumption of holes and thus inhibit the recombination with electrons. (3) the simultaneous introduction of B and S can engineer the electronic and energy level structural of g-C3N4 for optimizing interior charge transfer. Finally, the purpose of maximizing photocatalytic performance is achieved.