Depolymerization of Native Lignin over Thiol Capped Ultrathin ZnIn2S4 Microbelts Mediated by Photogenerated Thiyl Radical.

The valorization of native lignin to functionalized aromatic compounds under visible light is appealing yet challenging. In this communication, colloidal mercaptoalkanoic acid capped ultrathin ZnIn2S4 (ZIS) microbelts was successfully fabricated, which was used as a superior catalyst for depolymerization of native lignin in birch woodmeal under visible light, with an optimum yield of 28.8 wt% to functionalized aromatic monomers achieved in 8 h. The capped mercaptoalkanoic acid not only enables a solvent modulated reversible interchange of ZIS between the colloidal state for efficient reaction and the aggregated state for facile separation, but also serves as a precursor for light initiated generation of reactive thiyl radical for highly selective cleavage of ß-O-4 bond in native lignin. This work provides a green and efficient strategy for the depolymerization of native lignin to functionalized aromatic monomers under mild conditions, which involves a new mechanism for the cleavage of ß-O-4 bonds in native lignin. The capability of cleavage of ß-O-4 bonds in native lignin by photogenerated thiyl radicals also demonstrates the great potential of using photogenerated thiyl radicals in organics transformations.

Surface Oxygen Defect Engineering of A2B2O7 Pyrochlore Semiconductors Boosts the Electrocatalytic Reduction of CO2-to-HCOOH.

The electrocatalytic conversion of inert CO2 to value-added chemical fuels powered by renewable energy is one of the benchmark approaches to address excessive carbon emissions and achieve carbon-neutral energy restructuring. However, the adsorption/activation of supersymmetric CO2 is facing insurmountable challenges that constrain its industrial-scale applications. Here, this theory-guided study confronts these challenges by leveraging the synergies of bimetallic sites and defect engineering, where pyrochlore-type semiconductor A2B2O7 is employed as research platform and the conversion of CO2-to-HCOOH as the model reaction. Specifically, defect engineering intensified greatly the chemisorption-induced CO2 polarization via the bimetallic coordination, thermodynamically beneficial to the HCOOH production via the *HCO2 intermediate. The optimal V-BSO-430 electrocatalyst with abundant surface oxygen vacancies achieved a superior HCOOH yield of 116.7 mmol h-1 cm-2 at -1.2 VRHE, rivalling the incumbent similar reaction systems. Furthermore, the unique catalytic unit featured with a Bi1-Sn-Bi2 triangular structure, which is reconstructed by defect engineering, and altered the pathway of CO2 adsorption and activation to allow the preferential affinity of the suspended O atom in *HCO2 to H. As a result, V-BSO-430 gave an impressive FEHCOOH of 93% at -1.0 VRHE. This study held promises for inspiring the exploration of bimetallic materials from the massive semiconductor database.

Confined synthesis of conjugated microporous polymers for selective photocatalytic oxidation of amines.

Photocatalytic oxidative coupling of amines is considered a mild, efficient, and sustainable strategy for the synthesis of imines. As a versatile organic semiconductor, conjugated microporous polymers (CMPs) are attractive in photocatalysis areas due to the diversity of their polymeric monomers. Herein, we report that in addition to the design of monomers, size-confined polymerization is also a feasible strategy to modulate the structure and photocatalysis properties of CMPs. We adopted dibromopyrazine as polymeric units to prepare pyrazine-involved hollow spherical CMPs (H-PyB) using a template method and successfully performed size-confined polymerization of hollow samples by resizing the templates. Interestingly, the small confinement space induced the formation of CMPs with better conjugate extensibility, resulting in enhanced conductivity, narrowed bandgaps, improved photoelectric performance, etc. As a result, small-sized H-PyB CMPs had superior activity for the photocatalytic oxidation of amines. Particularly, the smallest H-PyB CMPs that we designed in the present work exhibited excellent performance for the photocatalytic coupling oxidation of amines. When using benzylamine as a model substrate, the yield of the corresponding imine reached âˆ¼ 113 mmol·g-1·h-1, accompanied by almost 100 % selectivity. Furthermore, the as-designed confined samples exhibited stable photocatalytic activity as well as good applicability for oxidative coupling of different amines. This work not merely reports a kind of CMP photocatalysts with excellent performance for the imine coupling oxidation but also proposes an alternative strategy for constructing high-performance organic photocatalysts by size-confined synthesis.

Tunable Band Engineering Management on Perovskite MAPbBr3 /COFs Nano-Heterostructures for Efficient S-S Coupling Reactions.

Efficient artificial photosynthesis of disulfide bonds holds promises to facilitate reverse decoding of genetic codes and deciphering the secrets of protein multilevel folding, as well as the development of life science and advanced functional materials. However, the incumbent synthesis strategies encounter separation challenges arising from leaving groups in the ─S─S─ coupling reaction. In this study, according to the reaction mechanism of free-radical-triggered ─S─S─ coupling, light-driven heterojunction functional photocatalysts are tailored and constructed, enabling them to efficiently generate free radicals and trigger the coupling reaction. Specifically, perovskites and covalent organic frameworks (COFs) are screened out as target materials due to their superior light-harvesting and photoelectronic properties, as well as flexible and tunable band structure. The in situ assembled Z-scheme heterojunction MAPB-M-COF (MAPbBr3 = MAPB, MA+ = CH3 NH2 + ) demonstrates a perfect trade-off between quantum efficiency and redox chemical potential via band engineering management. The MAPB-M-COF achieves a 100% ─S─S─ coupling yield with a record photoquantum efficiency of 11.50% and outstanding cycling stability, rivaling all the incumbent similar reaction systems. It highlights the effectiveness and superiority of application-oriented band engineering management in designing efficient multifunctional photocatalysts. This study demonstrates a concept-to-proof research methodology for the development of various integrated heterojunction semiconductors for light-driven chemical reaction and energy conversion.

Metal to non-metal sites of metallic sulfides switching products from CO to CH4 for photocatalytic CO2 reduction.

The active center for the adsorption and activation of carbon dioxide plays a vital role in the conversion and product selectivity of photocatalytic CO2 reduction. Here, we find multiple metal sulfides CuInSnS4 octahedral nanocrystal with exposed (1 1 1) plane for the selectively photocatalytic CO2 reduction to methane. Still, the product is switched to carbon monoxide on the corresponding individual metal sulfides In2S3, SnS2, and Cu2S. Unlike the common metal or defects as active sites, the non-metal sulfur atom in CuInSnS4 is revealed to be the adsorption center for responding to the selectivity of CH4 products. The carbon atom of CO2 adsorbed on the electron-poor sulfur atom of CuInSnS4 is favorable for stabilizing the intermediates and thus promotes the conversion of CO2 to CH4. Both the activity and selectivity of CH4 products over the pristine CuInSnS4 nanocrystal can be further improved by the modification of with various co-catalysts to enhance the separation of the photogenerated charge carrier. This work provides a non-metal active site to determine the conversion and selectivity of photocatalytic CO2 reduction.

Iron/cobalt/nickel regulation for efficient photocatalytic carbon dioxide reduction over phthalocyanine covalent organic frameworks.

Using solar photocatalytic CO2 reduction to produce high-value-added products is a promising solution to environmental problems caused by greenhouse gases. Metal phthalocyanine COFs possess a suitable band structure and strong light absorption ability, making them a promising candidate for photocatalytic CO2 reduction. However, the relationship between the electronic structure of these materials and photocatalytic properties, as well as the mechanism of photocatalytic CO2 reduction, is still unclear. Herein, the electronic structure of three MPc-TFPN-COFs (M = Ni, Co, Fe) and the reaction process of CO2 reduction to CO, HCOOH, HCHO and CH3OH were studied using DFT calculations. The calculated results demonstrate that these COFs have a good photo response to visible light and are new potential photocatalytic materials. Three COFs show different reaction mechanisms and selectivity in generating CO2 reduction products. NiPc-TFPN-COFs obtain CO through the reaction pathway of CO2 → COOH → CO, and the energy barrier of the rate-determining step is 2.82 eV. NiPc-TFPN-COFs and FePc-TFPN-COFs generate HCHO through CO2 → COOH → CO → CHO → HCHO, and the energy barrier of the rate step is 2.82 eV and 2.37 eV, respectively. Higher energies are required to produce HCOOH and CH3OH. This work is helping in understanding the mechanism of photocatalytic reduction of CO2 in metallophthalocyanine COFs.

Facile Preparation of the ZnSe/Ag2Se Binary Heterojunction for Photocatalytic Antibacterial Efficiency.

In a novel approach that capitalized on the differential solubility product (Ksp) of ZnSe and Ag2Se, a unique ZnSe/Ag2Se binary heterostructure was efficiently synthesized in situ. ZnSe/Ag2Se exhibited excellent antimicrobial efficiency under visible light. Incorporating Ag2Se into ZnSe significantly enhanced the photoelectric performance of the catalyst, greatly accelerating the separation of the photogenerated electrons in the system. Active species removal experiments determined that ·O2- and H2O2 played crucial roles in photocatalytic antibacterial efficiency. Further investigation into the levels of cellular membrane peroxidation, bacterial morphology, and intracellular contents concentration revealed that during the photocatalytic antimicrobial process, reactive oxygen species initially oxidize phospholipids in the cell membrane, leading to damage to the external structure of the cell and leakage of the intracellular contents, ultimately resulting in bacteria inactivation. The photocatalytic antimicrobial process of ZnSe/Ag2Se fundamentally deviates from conventional methods, offering new insights into efficient disinfection and photocatalytic antimicrobial mechanisms.

The Keto-Switched Photocatalysis of Reconstructed Covalent Organic Frameworks for Efficient Hydrogen Evolution.

The keto-switched photocatalysis of covalent organic frameworks (COFs) for efficient H2 evolution was reported for the first time by engineering, at a molecular level, the local structure and component of the skeletal building blocks. A series of imine-linked BT-COFs were synthesized by the Schiff-base reaction of 1, 3, 5-benzenetrialdehyde with diamines to demonstrate the structural reconstruction of enol to keto configurations by alkaline catalysis. The keto groups of the skeletal building blocks served as active injectors, where hot π-electrons were provided to Pt nanoparticles (NPs) across a polyvinylpyrrolidone (PVP) insulting layer. The characterization results, together with density functional theory calculations, indicated clearly that the formation of keto-injectors not only made the conduction band level more negative, but also led to an inhomogeneous charge distribution in the donor-acceptor molecular building blocks to form a strong intramolecular built-in electric field. As a result, visible-light photocatalysis of TP-COFs-1 with one keto group in the skeletal building blocks was successfully enabled and achieved an impressive H2 evolution rate as high as 0.96 mmol g-1 h-1 . Also, the photocatalytic H2 evolution rates of the reconstructed BT-COFs-2 and -3 with two and three keto-injectors were significantly enhanced by alkaline post-treatment.

Hierarchical Hollow-TiO2@CdS/ZnS Hybrid for Solar-Driven CO2-Selective Conversion.

Light-driven valorization conversion of CO2 is an encouraging carbon-negative pathway that shifts energy-reliance from fossil fuels to renewables. Herein, a hierarchical urchin-like hollow-TiO2@CdS/ZnS (HTO@CdS/ZnS) Z-scheme hybrid synthesized by an in situ self-assembly strategy presents superior photocatalytic CO2-to-CO activity with nearly 100% selectivity. Specifically, benefitting from the reasonable architectural and interface design, as well as surface modification, this benchmarked visible-light-driven photocatalyst achieves a CO output of 62.2 µmol·h-1 and a record apparent quantum yield of 6.54% with the Co(bpy)32+ (bpy = 2,2'-bipyridine) cocatalyst. It rivals all the incumbent selective photocatalytic conversion of CO2 to CO in the CH3CN/H2O/TEOA reaction systems. Specifically, the addition of HTO and stabilized ZnS enables the photocatalyst to effectively upgrade optical and electrical performances, contributing to efficient light-harvesting and photogenerated carrier separation, as well as interfacial charge transfer. The tremendous enhancement of photocatalytic performance reveals the superiority of the Z-scheme heterojunction assembled from HTO and CdS/ZnS, featuring the inner electric field derived from the band bending of HTO@CdS/ZnS make CdS resistant to photocorrosion. This study allows access to inspire studies on rationally modeling and constructing diverse heterostructures for the storage and conversion of renewables and chemicals.

Carbazole-involved conjugated microporous polymer hollow spheres for selective photocatalytic oxidation of benzyl alcohol under visible-light irradiation.

Conjugated microporous polymers (CMPs) have been considered a type of promising visible-light-driven, organic photocatalysts. However, apart from designing high-performance CMPs from a molecular perspective, little attention is paid to improving the photocatalytic properties of these polymers through macrostructural regulation. Herein, we prepared a kind of hollow spherical CMPs involving carbazole monomers and studied their performance on the selective photocatalytic oxidation of benzyl alcohol under visible light irradiation. The results demonstrate that the introduction of a hollow spherical structure improves the physicochemical properties of the as-designed CMPs, including the specific surface areas, optoelectronic characteristics, as well as photocatalytic performance, etc. In particular, the hollow CMPs can more effectively oxidize benzyl alcohol compared to pristine ones under blue light illumination, and produce >1 mmol of benzaldehyde in 4.5 h with a yield of up to 9 mmol·g-1·h-1, which is almost 5 times higher than that of the pristine ones. Furthermore, such hollow architecture has a similar enhanced effect on the oxidation of some other aromatic alcohols. This work shows that the deliberate construction of specific macrostructures can better arouse the photocatalytic activity of the as-designed CMPs, which will contribute to the further use of these organic polymer semiconductors in photocatalysis areas.

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

A series of novel surface Ru-H bipyridine complexes-grafted TiO2 nanohybrids were for the first time prepared by a combined procedure of surface organometallic chemistry with post-synthetic ligand exchange for photocatalytic conversion of CO2 to CH4 with H2 as electron and proton donors under visible light irradiation. The selectivity toward CH4 increased to 93.4% by the ligand exchange of 4,4'-dimethyl-2,2'-bipyridine (4,4'-bpy) with the surface cyclopentadienyl (Cp)-RuH complex and the CO2 methanation activity was enhanced by 4.4-fold. An impressive rate of 241.2 µL·g-1·h-1 for CH4 production was achieved over the optimal photocatalyst. The femtosecond transient IR absorption results demonstrated that the hot electrons were fast injected in 0.9 ps from the photoexcited surface 4,4'-bpy-RuH complex into the conduction band of TiO2 nanoparticles to form a charge-separated state with an average lifetime of ca. 50.0 ns responsible for the CO2 methanation. The spectral characterizations indicated clearly that the formation of CO2•- radicals by single electron reduction of CO2 molecules adsorbed on surface oxygen vacancies of TiO2 nanoparticles was the most critical step for the methanation. Such radical intermediates were inserted into the explored Ru-H bond to generate Ru-OOCH species and finally CH4 and H2O in the presence of H2.

Rational Design of a Core-Shell Structured Plasmonic Au@MIL-100(Fe) Nanocomposite for Efficient Photocatalysis.

The utilization of solar light to trigger organic syntheses for the production of value-added chemicals has attracted increasing recent research attention. The integration of plasmonic Au NPs (NPs = nanoparticles) with MOFs would provide a new way for the development of highly efficient photocatalytic systems. In this manuscript, a bottle-around-ship strategy was adopted for the successful synthesis of a core-shell structured Aupvp@MIL-100(Fe) (PVP = polyvinylpyrrolidone) nanocomposite in room temperature. The as-obtained core-shell structured Aupvp@MIL-100(Fe) show improved photocatalytic performance for benzyl alcohol oxidation under visible light, because of the migration of the surface plasmon resonance (SPR) excited hot electrons from plasmonic Au NPs to MIL-100(Fe), resulting in the production of more active O2•- radicals. The removal of the capping agent PVP from Aupvp@MIL-100(Fe) significantly enhanced the photocatalytic performance, because of an improved charge transfer from plasmonic Au NPs to MIL-100(Fe). This study demonstrates an efficient strategy of fabricating superior photocatalytic systems by a rational coupling of plasmonic Au NPs and photocatalytic active MOFs into a core-shell structured nanocomposite.

Near-Infrared Light-Driven Photoredox Catalysis by Transition-Metal-Complex Nanodots.

Developing light-harvesting materials with broad spectral response is of fundamental importance in full-spectrum solar energy conversion. We found that, when a series of earth-abundant metal (Cu, Co, Ni and Fe) salts are dissolved in coordinating solvents uniformly dispersed nanodots (NDs) are formed rather than fully dissolving as molecular species. The previously unrecognized formation of this condensed state is ascribed to spontaneous aggregation of molecular transition-metal-complexes (TMCs) via weak intermolecular interactions, which results in redshifted and broadened absorption into the NIR region (200-1100 nm). Typical photoredox reactions, such as carbonylation and oxidative dehydrogenation, well demonstrate the feasibility of efficient utilization of NIR light (λ>780 nm) by TMCs NDs. Our finding provides a conceptually new strategy for extending the absorption towards low energy photons in solar energy harvesting and conversion via photoredox transformations.

Plasma-assisted in-situ preparation of graphene-Ag nanofiltration membranes for efficient removal of heavy metal ions.

Graphene-based membranes have been considered as promising separation membranes for water treatments due to their unique two-dimensional confined channels. However, subject to the preparation technology, the effective construction of graphene-based filtration membranes with suitable separation ability on heavy metal ions still face considerable challenges. Herein, we have successfully constructed a kind of graphene-based (reduced graphene oxide, rGO) nanofiltration membranes by adopting a plasma-assisted in-situ photocatalytic reduction method. Graphene oxide-Ag (GO-Ag) composite sheets are prepared firstly and then assembled into membranes by vacuum filtration. With the use of Ag nanoparticles as plasmonic photocatalyst, GO-Ag films can be in-situ reduced, leading to the formation of rGO-based composite membranes. Thanks to the mild in-situ reduction process, the filtration ability on heavy metal ions (Cr(VI), Cr3+, Cu2+ and Pb2+) caused by lamellar structure is well retained in the as-formed rGO-Ag membranes. Especially, when treating the typical toxic Cr(VI) solution, the retention capacity, water flux and stability of rGO-Ag membranes are all improved compared with that of the original GO-Ag ones. In addition, the effectively rejection of Cr(VI) from mixed solutions containing both Cr(VI) and Cr(III) also suggests the good applicability of such rGO-Ag membranes in a complex wastewater system.

The Hole-Tunneling Heterojunction of Hematite-Based Photoanodes Accelerates Photosynthetic Reaction.

Single-atom metal-insulator-semiconductor (SMIS) heterojunctions based on Sn-doped Fe2 O3 nanorods (SF NRs) were designed by combining atomic deposition of an Al2 O3 overlayer with chemical grafting of a RuOx hole-collector for efficient CO2 -to-syngas conversion. The RuOx -Al2 O3 -SF photoanode with a 3.0 nm thick Al2 O3 overlayer gave a >5-fold-enhanced IPCE value of 52.0 % under 370 nm light irradiation at 1.2 V vs. Ag/AgCl, compared to the bare SF NRs. The dielectric field mediated the charge dynamics at the Al2 O3 /SF NRs interface. Accumulation of long-lived holes on the surface of the SF NRs photoabsorber aids fast tunneling transfer of hot holes to single-atom RuOx species, accelerating the O2 -evolving reaction kinetics. The maximal CO-evolution rate of 265.3 mmol g-1 h-1 was achieved by integration of double SIMS-3 photoanodes with a single-atom Ni-doped graphene CO2 -reduction-catalyst cathode; an overall quantum efficiency of 5.7 % was recorded under 450 nm light irradiation.

Stable lead-free perovskite solar cells: A first-principles investigation.

A suitable substitution of the lead element in lead-based halide perovskites is a feasible approach to explore lead-free perovskite material with excellent stability, tunable band gap, high optical absorption, and better photovoltaic performance. In this study, the toxic lead is replaced by mixing Ba/Si and Ba/Sn to develop environmentally friendly perovskite materials with excellent properties. MABa0.125Sn0.875I3 has shown evidently improved properties in terms of structural stability and suitable band gap, which indicates that MABa0.125Sn0.875I3 can become the most potential material for applications in single-junction solar cells. Moreover, MABa0.50Sn0.50I3 and MABa0.25Sn0.75I3 can be promising materials for the top cell in the tandem architecture due to their proper band gaps (1.70-1.80 eV). Moreover, the optical absorption coefficients of the proposed lead-free perovskites are stronger than that of MAPbI3 in the range of 500-800 nm. Our work can provide new insights into exploring lead-free perovskite solar cells with excellent stability and suitable band gap.

Exploring electronic and optical properties of Ge-based perovskites under strain: Insights from the first-principles calculations.

Organic-inorganic hybrid perovskites have attracted extensive attention as promising photovoltiac materials for high-efficiency solar cells. In this study, strain effects on the material properties of Ge-based perovskites are fully investigated by the first-principles calculations. The results indicate that the structural, mechanical, electronic and optical properties of CH3NH3GeX3 (X = Cl, Br, I) are sensitive to external modulations. The band gaps of three Ge-based halide perovskites are well predicted by using the HSE06 functional. By increasing the compressive strain, the band gaps of three compounds decrease. A suitable band gap (1.36 eV) of CH3NH3GeI3 can be obtained under a strain of -3%. Moreover, the calculated elastic constants further imply that this compound is stable under this condition. The relationship between the band gap variation and geometry change under the compressive strain is revealed. These results are useful for understanding the effects of strain on the material properties of semiconductors and guiding the experiments to improve photovoltaic performance of Ge-based perovskites.

Indirect-to-direct band gap transition and optical properties of metal alloys of Cs2Te1-x Ti x I6: a theoretical study.

In recent years, double perovskites have attracted considerable attention as potential candidates for photovoltaic applications. However, most double perovskites are not suitable for single-junction solar cells due to their large band gaps (over 2.0 eV). In the present study, we have investigated the structural, mechanical, electronic and optical properties of the Cs2Te1-x Ti x I6 solid solutions using first-principles calculations based on density functional theory. These compounds exhibit good structural stability compared to CH3NH3PbI3. The results suggest that Cs2TeI6 is an indirect band gap semiconductor, and it can become a direct band gap semiconductor with the value of 1.09 eV when the doping concentration of Ti4+ is 0.50. Moreover, an ideal direct band gap of 1.31 eV is obtained for Cs2Te0.75Ti0.25I6. The calculated results indicate that all the structures are ductile materials except for Cs2Te0.50Ti0.50I6. Our results also show that these materials possess large absorption coefficients in the visible light region. Our work can provide a route to explore stable, environmentally friendly and high-efficiency light absorbers for use in optoelectronic applications.

High-Rate, Tunable Syngas Production with Artificial Photosynthetic Cells.

An artificial photosynthetic (APS) system consisting of a photoanodic semiconductor that harvests solar photons to split H2 O, a Ni-SNG cathodic catalyst for the dark reaction of CO2 reduction in a CO2 -saturated NaHCO3 solution, and a proton-conducting membrane enabled syngas production from CO2 and H2 O with solar-to-syngas energy-conversion efficiency of up to 13.6 %. The syngas CO/H2 ratio was tunable between 1:2 and 5:1. Integration of the APS system with photovoltaic cells led to an impressive overall quantum efficiency of 6.29 % for syngas production. The largest turnover frequency of 529.5 h-1 was recorded with a photoanodic N-TiO2 nanorod array for highly stable CO production. The CO-evolution rate reached a maximum of 154.9 mmol g-1 h-1 in the dark compartment of the APS cell. Scanning electrochemical-atomic force microscopy showed the localization of electrons on the single-nickel-atom sites of the Ni-SNG catalyst, thus confirming that the multielectron reduction of CO2 to CO was kinetically favored.

Layered Heterostructures of Ultrathin Polymeric Carbon Nitride and ZnIn2 S4 Nanosheets for Photocatalytic CO2 Reduction.

The rational construction of heterostructures by using layered semiconductors with two-dimensional (2D) nanosheet configurations is promising to improve the efficiency of CO2 photoreduction. Herein, the fabrication of layered heterojunction photocatalysts (PCN/ZnIn2 S4 ) by in situ growth of 2D ZnIn2 S4 nanosheets on the surfaces of ultrathin polymeric carbon nitride (PCN) layers is presented for greatly enhanced CO2 conversion with visible light. The solution-processed self-assembly strategy renders the building of uniform and intimate junctions between PCN layers and ZnIn2 S4 subunits, which remarkably accelerates the separation and transfer of photogenerated charge carriers. In addition, the layered composites can also promote CO2 adsorption and strengthen the visible-light absorption. Consequently, the optimized PCN/ZnIn2 S4 sheet-shaped composite shows reinforced photoactivity for deoxygenative CO2 conversion, affording a high CO-production rate of 44.6 µmol h-1 , which is 223 times higher than that of the pristine PCN nanosheets. Moreover, the heterojunction photocatalyst also exhibits high stability during repeated runs for five cycles.