Synergistic Catalytic Mechanism Research Articles

Tailored synthesis of plate-like SAPO-11 molecular sieve and its application in non-noble metal-supported catalyst for efficient hydroisomerization of long-chain n-alkanes

The tailored synthesis of plate-like SAPO-11 molecular sieve was achieved by introducing seed-surfactant directing agent into the synthesis system for the first time. The effects of morphological change of SAPO-11 molecular sieve on the physicochemical properties of SAPO-11 and the active phase properties of the catalyst were analyzed via a series of characterization techniques. The hydroisomerization of n-hexadecane was used as the model reaction to evaluate the catalytic performance of NiWS supported catalysts based on SAPO-11 molecular sieve with different morphologies. The plate-like SAPO-11 possessed better textural properties and acidity than pseudo-spherical SAPO-11. Meanwhile, the stacking number, dispersion and metal sulfidation degree of the active phase of sulfided NiW/SAPO-11-P were improved, and its high proportion of type II active phase optimized the metal–acid synergistic catalytic mechanism. Through tracking and analyzing the crystallization process of plate-like SAPO-11, the formation mechanism of plate-like SAPO-11 was investigated and revealed. The adsorption kinetics, diffusion behavior and catalytic kinetics of n-hexadecane on the catalysts were emphatically investigated. The optimized support structure and active phase properties improved the intrinsic catalytic activity and hydroisomerization reaction path priority of NiW/SAPO-11-P. It was found that the hydroisomerization reaction on NiW/SAPO-11-P was carried out under the reaction-limiting conditions, while the hydroisomerization reaction on NiW/SAPO-11-C was carried out under the reaction-controlling conditions. The effects of plate-like SAPO-11 on the activity stability of the catalyst was investigated, and the essential reasons for the differences in activity stability of the catalysts were revealed through comprehensively analyzing the coke formation difference and diffusion behavior difference. It is expected to provide reference for the tailored design of SAPO-11 molecular sieve with special morphology and the preparation of efficient hydroisomerization catalyst.

Gamma-valerolactone-enabled control chemoselective conversion of glucose to 1,6-anhydroglucose over HZSM-5 zeolite

Unraveling chemoselective catalysis in the upgrading of renewable biomass-derived molecules to fine chemicals and bio-fuels is particularly challenging. Here, we report an innovative strategy for the chemocatalytic conversion of glucose into 1,6-anhydroglucose, a high-value platform molecule, in γ-valerolactone (GVL) over HZSM-5 (50) zeolite. In this case, HZSM-5 (50) zeolite exhibits remarkable shape-selective catalytic performance with a high turn-over frequency (TOF) of 201.6 h−1 and a 1,6-anhydroglucose selectivity of 95.3%. Solvent effect study from both experimental and theoretical results suggests the usage of solvent GVL is particularly beneficial for glucose diffusion into the zeolite pore channel, accelerating the isomerization-dehydration process. Kinetic behavior description of glucose transformation to 1,6-anhydroglucose is developed to monitor the process, whereas a synergistic catalytic mechanism is elucidated in detail by density functional theory calculations. Such solvent-induce and shape-selective catalytic system provides a compelling strategy for highly selective production of 1,6-anhydroglucose as a biomass platform molecule.

Hydroxyl and amino dual-functionalized core-shell molecular sieves featuring hydrogen bond donor groups for efficient CO2 cycloaddition

In CO2 cycloaddition reactions, hydrogen bond donor (HBD) groups are considered environmentally friendly substitutes for metals to promote epoxide ring-opening through interactions with nucleophilic anions. A core-shell structured ILs-based catalyst (mSiO2@MCM-NH2-OH) with dual hydrogen bond donors (–OH and –NH2) was synthesized by copolymerization strategy. Through in-depth characterization, it has been demonstrated that the catalyst (mSiO2@MCM-NH2-OH) possesses multiple catalytic active sites including –OH, –NH2, Br- groups, and the synergistic effect of double HBD groups (–OH and –NH2) and Lewis base (Br-) significantly improved the catalytic activity. Meanwhile, the core-shell structure of the catalyst effectively prevents the loss of active components, which makes the yield remain at about 94 % after 10 cycles. Based on Density Functional Theory (DFT) calculations, a synergistic catalytic mechanism, which involves dual hydrogen-bond donors (–OH and –NH2) and Lewis bases (Br-) was proposed. The cooperative interaction between –OH/–NH2 and Br- reduced the ring-opening barrier of epoxide from 58.6 to 32.0 kcal mol−1 significantly, and thereby facilitated the CO2 cycloaddition reaction.

Design of Magnetic Fe3O4/CeO2 "Core/Shell"-Like Nanocomposites with Pronounced Antiamyloidogenic and Antioxidant Bioactivity.

"Core/shell" nanocomposites based on magnetic magnetite (Fe3O4) and redox-active cerium dioxide (CeO2) nanoparticles (NPs) are promising in the field of biomedical interests because they can combine the ability of magnetic NPs to heat up in an alternating magnetic field (AMF) with the pronounced antioxidant activity of CeO2 NPs. Thus, this report is devoted to Fe3O4/CeO2 nanocomposites (NCPs) synthesized by precipitation of the computed amount of "CeO2-shell" on the surface of prefabricated Fe3O4 NPs. The X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy data validated the formation of Fe3O4/CeO2 "core/shell"-like NCPs, in which ultrafine CeO2 NPs with an average size of approximately 3-3.5 nm neatly surround Fe3O4 NPs. The presence of a CeO2 "shell" significantly increased the stability of Fe3O4/CeO2 NCPs in aqueous suspensions: Fe3O4/CeO2 NCPs with "shell thicknesses" of 5 and 7 nm formed highly stable magnetic fluids with ζ-potential values of >+30 mV. The magnetization values of Fe3O4/CeO2 NCPs decreased with a growing CeO2 "shell" around the magnetic NPs; however, the resulting composites retained the ability to heat efficiently in an AMF. The presence of a CeO2 "shell" generates a possibility to precisely regulate tuning of the maximum heating temperature of magnetic NCPs in the 42-50 °C range and stabilize it after a certain time of exposure to an AMF by changing the thickness of the "CeO2-shell". A great improvement was observed in both antioxidant and antiamyloidogenic activities. It was found that inhibition of insulin amyloid formation, expressed in IC50 concentration, using NCPs with a "shell thickness" of 7 nm was approximately 10 times lower compared to that of pure CeO2. For these NCPs, more than 2 times higher superoxide dismutase-like activity was observed. The coupling of both Fe3O4 and CeO2 results in higher bioactivity than either of them individually, probably due to a synergistic catalytic mechanism.

Constructing asymmetric double-atomic sites for synergistic catalysis of electrochemical CO2 reduction

Elucidating the synergistic catalytic mechanism between multiple active centers is of great significance for heterogeneous catalysis; however, finding the corresponding experimental evidence remains challenging owing to the complexity of catalyst structures and interface environment. Here we construct an asymmetric TeN2–CuN3 double-atomic site catalyst, which is analyzed via full-range synchrotron pair distribution function. In electrochemical CO2 reduction, the catalyst features a synergistic mechanism with the double-atomic site activating two key molecules: operando spectroscopy confirms that the Te center activates CO2, and the Cu center helps to dissociate H2O. The experimental and theoretical results reveal that the TeN2–CuN3 could cooperatively lower the energy barriers for the rate-determining step, promoting proton transfer kinetics. Therefore, the TeN2–CuN3 displays a broad potential range with high CO selectivity, improved kinetics and good stability. This work presents synthesis and characterization strategies for double-atomic site catalysts, and experimentally unveils the underpinning mechanism of synergistic catalysis.

Efficient Synthesis of Furfural from Corncob by a Novel Biochar-Based Heterogeneous Chemocatalyst in Choline Chloride: Maleic Acid–Water

The use of plentiful and renewable feedstock for producing chemicals is fundamental for the development of sustainable chemical processes. Using fish scale as a biobased carrier, a novel biochar SO42−/SnO2-FFS heterogeneous chemocatalyst was prepared to catalyze furfural production from xylose-rich corncob-hydrolysates obtained from acid hydrolysis of corncob in a deep eutectic solvent (DES)–water system. By characterizing the physical as well as chemical properties of SO42−/SnO2-FFS by NH3-TPD, FT-IR, XPS, XRD, and SEM, it was shown that the chemocatalyst had Lewis/Brönsted acid centers, and its surface roughness could be well expanded to contact substrates. The corncob was initially hydrolyzed at 140 °C to obtain xylose-rich hydrolysate. Subsequently, SO42−/SnO2-FFS (3.6 wt.%) was used to catalyze the corn cob hydrolysate containing D-xylose (20.0 g/L) at a reaction temperature of 170 °C for 15 min. Additionally, ZnCl2 (20.0 g/L) was added. Ultimately, furfural (93.8 mM, 70.5% yield) was produced in the deep eutectic solvent ChCl:maleic acid–water (DESMLA–water = 10:90, v/v). A synergistic catalytic mechanism for transforming xylose-rich corncob-hydrolysate into furfural and byproducts were proposed using SO42−/SnO2-FFS as a chemocatalyst in DESMLA–water containing ZnCl2. Consequently, the efficient use of biochar SO42−/SnO2-FFS chemocatalysts for the sustainable synthesis of biobased furan compounds from biomass holds great promise in the future.

A DFT study on the copper-single-atom modified 2D electride Ca2N monolayer for ethanol dehydrogenation

Two-dimensional (2D) electrides, with electrons confined in interlayer spaces instead of at atomic proximities, have received considerable attention due to their exotic properties. However, the current exploration of electrides in the field of catalysis urgently needs to be expanded. Here, we report novel thermodynamically stable Cu single-atom-modified 2D electride Ca2N monolayer catalysts for ethanol dehydrogenation using density functional theory calculations. The interaction and synergistic catalytic mechanism of copper single atoms and Ca2N monolayers were thoroughly revealed. The coordination environment of copper greatly affects the reaction sites for ethanol dehydrogenation. Furthermore, it was found that the strong electron transfer ability of Ca2N monolayer promoted the adsorption and activation of ethanol molecules on the catalyst, resulting in a cleavage energy barrier of the O–H bond as low as 0.29 eV on Cu1/Ca2N. Furthermore, turnover frequency (TOF) analysis demonstrates that Cu1/Ca2N exhibits significantly higher activity compared to Ca2N with lower energetic span (δE) of 2.52 eV at 298.15 K for the cycle of ethanol dehydrogenation to acetaldehyde. Our work demonstrates a new avenue to the discovery of 2D electride-based catalysts and provides new insights into the mechanism of ethanol dehydrogenation.

MOF-derived FeCo carbon nanomaterials with abundant oxygen vacancies as highly efficient peroxymonosulfate catalyst for ciprofloxacin degradation

In this work, the FeCo-NB@C catalysts were prepared via calcination with FeCo-MOF as a precursor for highly efficient activation of peroxymonosulfate (PMS). SEM and XPS indicated that FeCo-NB@C possesses mass metal active sites and abundant oxygen vacancies. A synergistic effect (synergy indices 4.6) was observed in the FeCo-NB@C600/PMS process. The ciprofloxacin (CIP) could be almost degraded completely within 15 min in the optimal conditions. It was noted that FeCo-NB@C600/PMS process still performed well on CIP removal under multiple inorganic anions and real water matrix conditions. Radical quenching experiments, EPR analysis, and contribution calculation identified that SO4•−, •OH, and other ROS (O2•− and 1O2) played dominant role in CIP degradation, accounting for 60.24%, 20.19%, and 17.46%, respectively. The redox cycle of Co2+/Co3+ and Fe2+/Fe3+ induced the production of SO4•− and further formed •OH, etc. In addition, the formation of O2•− was confirmed by the role of oxygen vacancies rather than O2 through a series of designed experiments. Furthermore, the characterization results illustrated that FeCo-NB@C600 was largely unchanged with low ion leaching after three times cycles in PMS activated process, indicating the excellent stability and reusability of FeCo-NB@C600. Finally, the results of CIP degradation pathways and toxic evaluation revealed the low ecotoxicity of the intermediate products. This study demonstrates the synergistic catalytic mechanism of bimetallic catalysts in the persulfate activation, promising to realize sustainable and efficient water treatment technology.

Electrocatalysis of Fe‐N‐C Bonds Driving Reliable Interphase and Fast Kinetics for Phosphorus Anode in Sodium‐Ion Batteries

AbstractPhosphorus exhibits high capacity and low redox potential, making it a promising anode material for future sodium‐ion batteries. However, its practical applications are confined by poor durability and sluggish kinetics. Herein, an innovative in‐situ electrochemically self‐driven strategy is presented to embed phosphorus nanocrystal (≈10 nm) into a Fe‐N‐C‐rich 3D carbon framework (P/Fe‐N‐C). This strategy enables rapid and high‐capacity sodium ion storage. Through a combination of experimental assistance and theoretical calculations, a novel synergistic catalytic mechanism of Fe‐N‐C is reasonably proposed. In detail, the electrochemical formation of Fe‐N‐C catalytic sites facilitates the release of fluorine in ester‐based electrolyte, inducing Na+‐conducting‐enhanced solid‐electrolyte interphase. Furthermore, it also effectively induces the dissociation energy of the P‐P bond and promotes the reaction kinetics of P anode. As a result, the unconventional P/Fe‐N‐C anode demonstrates outstanding rate‐capability (267 mAh g−1 at 100 A g−1) and cycling stability (72%, 10 000 cycles). Notably, the assembled pouch cell achieves high‐energy density of 220 Wh kg−1.

Construction of Hydrophobic Ammonium Perchlorate with Synergistic Catalytic Effect Based on Supramolecular Self-Assembly for Synchronously Catalyzing the Thermal Decomposition of Ammonium Perchlorate and the Combustion of Aluminum.

Ammonium perchlorate (AP), as an important additive component of composite propellants, is critical to the combustion performance of propellants. Herein, AP@1H,1H,2H,2H-perfluorodecyltrichlorosilane (AP@PF) was prepared by establishing a tannic acid-iron ion (TA-Fe) supramolecular self-assembly layer on the AP surface and connecting the 1H,1H,2H,2H-perfluorodecyltrichlorosilane interfacial layer. Results demonstrate that TA-Fe and 1H,1H,2H,2H-perfluorodecyltrichlorosilane are uniformly bound to the surface layer of AP. AP@PF has a lower high-temperature thermal decomposition peak compared to AP. Meanwhile, the exothermic values of low-temperature thermal decomposition (338 J/g) and high-temperature thermal decomposition (597 J/g) of AP@PF are significantly higher than those of AP. In addition, AP@PF exhibits different surface interfacial properties, such as floating on the water surface and exhibiting a static contact angle of 105° on water. AP@PF shows almost no moisture absorption after aging in humid air for 30 days. The exothermic value of the mixture of AP@PF and aluminum powder (156 J/g) is significantly higher than that of the mixture of AP and aluminum (54 J/g), and the mixture of AP@PF and aluminum powder exhibits a higher calorific value and a stronger emission spectrum. Finally, the synergistic catalytic mechanism of AP@PF on the thermal decomposition of AP and the combustion of aluminum powder is also discussed.

An S-scheme CeO2/ foveolate g-C3N4 composite with horseradish peroxidase activity for photo-enzyme synergistic catalytic degradation of phenanthrene

Nanozyme technology is a relatively new technology that has shown promising applications in the removal of water pollutants. This study utilized a CeO2/foveolate g-C3N4 (CeO2/FCN) composite with S-scheme heterojunction to achieve efficient removal of Phenanthrene (PHE) through a combination of photocatalytic and enzymatic reactions. The S-scheme heterojunction was effective in inhibiting the recombination of photogenerated electron hole pairs, which promoted the generation of·OH and·O2-. Additionally, activated H2O2 enables Ce to achieve redox cycle reaction and generate more·OH for catalytic degradation, effectively improving the concentration of active species and promoting the photo-enzyme synergistic catalytic performance. The experimental results showed that PHE degradation efficiency of CeO2/FCN composite could reach 96.6% in 60 min. Furthermore, the photo-enzyme synergistic catalytic mechanism of CeO2/FCN composite and the possible intermediates generated in the degradation process were studied. The highly toxic PHE was converted into non-toxic green degradation products, providing an effective method for the photo-enzyme synergistic catalytic degradation of PAHs.

Ultrathin Bi4O5I2 nanosheets as an integrated piezo-photocatalyst: Super visible-light piezo-photocatalysis and synergistic catalytic mechanism

Coupling piezocatalysis in the process of photocatalysis has aroused great interests of researchers to depress the serious recombination of photogenerated charge carriers. However, it still suffers from the inefficient catalytic activity and lacks in-depth understanding on their relationship. In this work, we report that outstanding piezo-photocatalytic activity is achieved over ultrathin Bi4O5I2 nanosheets, and disclose the synergistic catalytic mechanism. Piezoelectric force microscopy (PFM) and COMSOL simulation analysis reveal the strong piezoelectricity of the Bi4O5I2. Under simultaneous irradiation of visible light and ultrasonic, Bi4O5I2 ultrathin nanosheets exhibit a piezo-photocatalytic efficiency of tetracycline hydrochloride (TH) degradation of 88.3% within 8 min with a rate coefficient of 0.4703 min−1, which is 2.3-fold of the sum of the single photocatalysis and piezocatalysis, also far exceeding that of other previously reported piezo-photocatalyst. In situ electrochemical and electron paramagnetic resonance (EPR) under light, ultrasonic, and simultaneous light and ultrasonic conditions disclose that the synergistically enhanced charge separation and transfer and evolution of reactive species (superoxide radicals and holes) occur in the piezo-photocatalytic reaction process, which is derived from the piezoelectric field and band bending. This work emphasizes the effect of the piezoelectric field on strengthening the photocatalytic performance and further the understanding on synergistic piezo-photocatalytic mechanism.

Acid-base bicentric ionic liquids catalytic reaction of EG and CO2 into carbonates enhanced by styrene oxide

In view of the harsh conditions of cyclic esterification reaction of ethylene glycol (EG) and carbon dioxide (CO2) to synthesize ethylene carbonate (EC), the yield is low and the catalysts are mostly metals, a series of green acid-base bicentric ionic liquids (ABbILs) were developed. Among them, the ABbILs of 1,5,7-Triazabicyclo[4.4.0]dec‑5-ene glutarimide ([TBDH][Glu]) had the best catalytic performance. Under the optimal reaction conditions, the yield of EC reached 29.5%, which was higher than most of the conventional metal-based catalysts. Through activity screening results and DFT calculation, it was found that different cations affect the interaction between N on anion and H proton of EG, and the H on the cation can activate the O on EG, which would affect the ability of ABbILs to activate EG. The acid-base bicentered synergistic catalytic mechanism of Bronsted acid and Lewis base was proposed by characterization and DFT calculation. This study opens up new avenues for the efficient conversion of diols and CO2 for the preparation of cyclic carbonates.

Nanoarchitectonics of polymeric crown-ether analog of Tröger base combined with potassium iodide and acids synergy in fixation of CO2 and epoxides

Tröger's bases (TB) containing two steric nitrogen atoms, are alternated as building block for constructing molecular acceptors to form covalent bonds with acids, making TB a promising catalyst. Herein, TB analogs fabricated with crown ethers were knitted by condensation reaction and combined with potassium iodide as a brand-new catalytic system (CATB-KIs), which were characterized using FT-IR, 13C CP MAS NMR, SEM, TGA, and XPS spectroscopy respectively. The generated CATB-KIs exhibited excellent performance for CO2 fixation reaction with epoxides to produce cyclic carbonates under mild conditions, and the catalytic activity could be further improved by coordinating with acids beforehand, in which HBr performs fascinated activity. After 12 h, the corresponding cyclic carbonate from epichlorohydrin with 95.1% yield was detected at mild conditions with solvent-free in the presence of CATB-KI-2 and HBr. A series of terminal epoxides were converted into desired cyclic carbonates with desirable yields. The catalyst could be recovered successfully and reused six times without significant loss of activity. Finally, dynamics study on catalytic mechanism has been accomplished and the activated energy was calculated as 72.1 kJ/mol. A synergistic catalytic mechanism of hydrogen bonding and I anion has been proposed to account for the excellent catalytic activity of this catalysts.

A series of bifunctional metalloporphyrins as efficient catalysts for cycloaddition of CO2 with epoxides

Two porphyrins, named H2TEtImP and H2DEtImP, with the four and two N‐ethylated imidazole groups, respectively, as well as their metalloporphyrins, M‐TEtImP (M = Zn, Mn, Co, Mg) and Zn‐DEtImP, were synthesized and characterized by ultraviolet–visible (UV–Vis), mass spectrometry (MS), proton nuclear magnetic resonance (1H NMR), and Fourier transform infrared (FTIR) successfully. The catalytic activity of these newly synthesized porphyrins with metal centers and halogen ions as variables on the cycloaddition reaction between carbon dioxide (CO2) and epoxides was investigated under solvent‐free conditions. The experimental results strongly verified that both halogen ions and metal centers were indispensable active sites. The metal catalytic activity increased in the order Co < Mn < Mg < Zn. The turnover frequency (TOF) of Zn‐TEtImP for the cycloaddition reaction of CO2 and epichlorohydrin was as high as 2213 h−1 (120°C, 1 MPa CO2, 6 h). Moreover, the wide applicability of Zn‐TEtImP to this reaction was demonstrated by substrate extension experiments, and the excellent recyclability of Zn‐TEtImP was confirmed. Finally, the synergistic catalytic mechanism of Lewis acid (metal center) and nucleophile (Br−) was proposed based on the catalytic results.

Unraveling the Synergistic Mechanism of Bi‐Functional Nickel–Iron Phosphides Catalysts for Overall Water Splitting

AbstractNi–Fe bimetallic electrocatalysts are expected to replace existing precious metal catalysts for water splitting and achieve industrial applications due to their high intrinsic activity and low cost. However, the mechanism by which Ni and Fe species synergistically enhance catalytic activity remains obscure, which still needs further in‐depth study. In this study, a highly active bi‐functional electrocatalyst of Ni2P/FeP heterostructures is constructed on Fe foam (Ni2P/FeP‐FF), clearly illustrating the effect of Ni on Fe species for oxygen evolution reaction (OER) and revealing the true catalytic active phase for hydrogen evolution reaction (HER). The Ni2P/FeP‐FF only needs overpotentials of 217 and 42 mV to reach 10 mA cm−2 for OER and HER, respectively, exhibiting superior bi‐functional activity for overall water splitting. The Ni can elevate the strength of FeO on Ni2P/FeP‐FF surface and promote the formation of high‐valence FeOOH phase during OER, thus enhancing OER performance. Based on first‐principles calculations and Raman characterizations, the Ni2P/Ni(OH)2 heterojunction evolved from Ni2P/FeP is identified as the real high active phase for HER. This study not only builds a near‐commercial bifunctional electrocatalyst for overall water splitting, but also provides a deep insight for synergistic catalytic mechanism of Ni and Fe species.

Cycloalkanes oxidation with O2 in high-efficiency and high-selectivity catalyzed by 3D MOFs with limiting domain and Zn(AcO)2 through synergistic mode

To achieve efficient and selective cycloalkane oxidation, binary catalytic systems had been constructed on the basis of 3D MOFs [Zr6O4(μ3-OH)4(Metalloporphyrin)2(μ1-OH)4(μ1-H2O)4] and Zn(AcO)2. MOFs were prepared to construct limiting domains to suppress diffusiveness of free radicals under disorder state, and Zn(AcO)2 had been employed as synergistic catalysis sites. Catalytic system constructed by PCN-222-d(Co) and Zn(AcO)2 exhibited excellent catalytic performance. In contrast to T(4-COOCH3)PPCo as homogeneous catalyst, an enhancement from 3.83% to 5.51% was obtained from conversion, meanwhile selectivity was increased from 79.9% to 94.4% in cyclohexane oxidation. Primary source of the excellent performance were inhibition of diffusiveness of free radicals under disorder state, and enhancement on C-H bonds oxidation with oxidation intermediate R-OOH catalyzed by Zn(II). Synergistic catalysis process and catalytic mechanism were investigated via controlled experiments, radical trapping, and EPR analyses. This study provides a useful reference for oxidative functionalization of cycloalkanes with O2, and a significant contribution for other chemical conversions involving in free radicals.

Urea-H2O2 defect engineering of δ-MnO2 for propane photothermal oxidation: Structure-activity relationship and synergetic mechanism determination

Photothermal catalysis has an advantage in effective and economical elimination technology of volatile organic compounds (VOCs) in the ascendant. Herein, various surface defect engineering routes were adopted to enhance the low-temperature propane oxidation of δ-MnO2. Compared to reducing etchants urea and vitamin C, δ-MnO2 treated with urea - H2O2 exhibited an excellent thermal (T90 = 240 ℃) and photothermal (T90 = 196 ℃) activities of propane oxidation. Urea - H2O2 treatment provided high concentration of Mn4+ and surface-active oxygen (Mn4+-Osur) species as surface-active sites, and produced numerous oxygen vacancies to improve charge separation and superoxide species generation capacity. Thus, the photothermal conversion efficiency and low-temperature reducibility were remarkably enhanced. Furthermore, the photothermal synergistic catalytic mechanism was proposed based on in-situ diffuse reflectance infrared Fourier transform spectroscopy and control experiments. The strategy here offered insight into the rational design of efficient transition catalysts, and in-depth understanding of the photothermal catalytic VOCs removal mechanism.

The synergistic catalytic mechanism between different functional sites of boron/iron on iron oxides in Fenton-like reactions

The detoxification and harmless treatment of toxic organic industrial wastewater are essential guarantees for the global water environment and human life safety. As an important treatment technology for this wastewater, the advanced oxidation process is limited by the catalytic rate due to the low reduction rate, and the modulation and acceleration of electron transfer at the catalytic sites become the focus and difficulty in this field. Herein, we synthesized boron-doped iron oxide (FeOx-B) to enhance the interfacial electron transfer during peroxymonosulfate (PMS) catalysis, resulting in efficient degradation (91.73 %) of the contaminant (TTCH, Tetracycline hydrochloride). Compared with the commercial Fe2O3 and Fe3O4, the removal rate of TTCH is improved by 47.89 % and 24.45 %, respectively. As a new active site, B-O interacts with the contaminant and accelerates the reduction of Fe (III). The reactive species also change from sulfate radical (SO4−), hydroxyl radical (OH), and singlet oxygen (1O2) to surface reactive complexes. The system is pH-adaptive (pH = 3–11) and presents excellent resistance to humic acid (HA) and anions (10 mM). Toxicity assessment reveals that the degradation products are low toxic or harmless. This work suggests a new strategy for the development of highly reactive iron-based materials and provides theoretical insights into the mechanism of the PMS activation processes.

Aboundent oxygen defects in CoFe-LDH derivatives for enhanced photo-thermal synergistic catalytic hydrogen production from NaBH4

Two-dimensional catalysts, which are sensitive to visible light and have a photothermal effect, can be used to catalyse the release of H2 from sodium borohydride (NaBH4) are being actively explored in energy saving systems. In this work, oxygen vacancy enriched two-dimensional CoFe-layered double hydroxide (CoFe-LDH) derivatives (named as CoFe-x °C, x = 200–500) have been explored for NaBH4 hydrolysis catalyzed by photo-thermal synergy without external heat source. The CoFe-300 °C presents its initial hexagonal lamellar structure and has the highest concentration of oxygen vacancy. These unique properties guarantee its excellent photo-thermal synergistic catalytic performance, achieving hydrogen production rate of 1877.5 mmol g−1 h−1, and maintains high efficiency after 5 cycles. This enhanced photo-thermal synergistic catalytic mechanism is the •OH (generated from h+ and H2O) attacks BH4− (absorbed on Ov sites) to produce H2, the heat from photothermal conversion accelerates the adsorption ability and attacking rate. This study opens a new strategy for the synergistic photo-thermal catalytic hydrolysis of NaBH4.