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•Three Fe-based MOFs have been applied to adsorption PFOA.•Response surface methodology is used to study interactions of parameters.•Adsorption micro-mechanism of PFOA has been ...provided using theoretical calculation.•Contributions of pore windows to PFOA adsorption are investigated.
Adsorption performance, interfacial interaction mechanism and contribution of pores concerning PFOA adsorption to Fe-based metal-organic frameworks (MOFs) including Fe-BTC, MIL-100-Fe and MIL-101-Fe are investigated using experiments and computational calculation at molecular level even electronic level. Fe-BTC (418 mg/g) with more Lewis acid sites demonstrates higher adsorption capacity of PFOA in comparison with MIL-100-Fe (349 mg/g) and MIL-101-Fe (370 mg/g). Adsorption isotherms and kinetics indicate presence of monolayer adsorption and chemisorption in adsorption process. The pH dependence of PFOA adsorption to Fe-based MOFs is statistically revealed by experiments and analysis of variance of response surface methodology (RSM). XPS spectra of MOF-PFOA corroborate that decreasing binding energy of Fe2p and increasing binding energy of F1s, suggesting the presence of Lewis acid/base complexing (LAB) and hydrophobic interaction in adsorption process. Differential charge demonstrates that Fe center and benzene of organic ligands are respectively electron acceptor and donor in adsorption process. Electronic level mechanism finds that LAB complexing dominates adsorption process due to highest overlap of electron cloud. Smaller pores such as triangle and pentagonal pores of Fe-based MOFs contribute to the load of PFOA, while larger hexagonal one enable PFOA to enter into cages, as revealed by computational calculation.
•A Z-scheme CdS/WS2 heterojunction with built-in electric field was successfully constructed.•Z-scheme configuration is confirmed through experiments and DFT calculations.•Photogenerated carrier ...separation and transfer was accelerated at the interface.•Excellent ability for photocatalytic degradation and mineralization of dyes and reduction of Cr(VI) is exhibited.•CdS/WS2 heterojunction has excellent stability and photocorrosion resistance.
In this work, Z-scheme CdS/WS2 heterojunctions with high-efficiency photocatalytic degradation for organic dyes and photoreduction for Cr(VI) were designed using a straightforward and green two-step hydrothermal method. Tuning the molar ratio of CdS and WS2 can effectively adjust the energy band structure in CdS/WS2 composites with the enhancement of separation efficiency for photogenerated electron-hole and the decrease in the recombination for photogenerated carrier, which leads to the improved photocatalytic activities. A highest photocatalytic activity is obtained for the CdS/WS2 composite with 30% WS2, where the apparent rate constant of RhB and the reduction rate of Cr(VI) are 0.06153 and 0.0846 per min, respectively. According to Density functional theory (DFT), the work function of CdS crystal surface is smaller than that of WS2. The trapping experiment indicates that, during the photocatalytic reaction, O2– and h+ are the two predominant active species. Notably, both experimental and theoretical analyses confirm the formation of Z-scheme heterojunctions with built-in electric fields in CdS/WS2 composite. In addition, the CdS/WS2 photocatalysts maintain good stability after four cycles of photocatalytic degradation of RhB and reduction of Cr(IV). Combing with the DFT calculations, a possible photocatalytic mechanism is proposed. Further, this study brings out a unique strategy for the construction of CdS based Z-scheme heterojunctions and the applications in remediation of polluted environment.
Subnanometric Pt-Ga alloy clusters were encapsulated in MFI zeolite frameworks for n-hexane dehydrogenation. The introduction of Ga species in small amounts significantly improves the catalytic ...activity and stability of Pt clusters and effectively avoids the deep dehydrogenation. Excess Ga (>0.10 wt%) not only exhibits the negative electronic effect of Pt-Ga alloys, but instead forms a large number of L acid sites in the catalyst, which promotes cyclisation and catalytic cracking reactions.
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•Synthesis of novel bimetallic Pt-Ga clusters in Silalite-1 zeolites by a ligand-protected direct H2 reduction method;•Remarkably promotion of the catalytic activity and stability by introduction of Ga species to Pt form GaPt3 alloy clusters.•The electronic effect in PtGa@S-1 hinders the deep dehydrogenation on metal surfaces and inhibit coke formation.•0.4Pt0.04 Ga@S-1-H exhibited the highest catalytic activity, selectivity and stability in the dehydrogenation of light naphtha to mono-olefins.
Dehydrogenation of light naphtha followed by catalytic cracking into high-value end products can meet the high demand in the world’s petrochemical market. In this work, at attempting synthesis of novel catalysts for hexane dehydrogenation, a series of bimetallic Pt-Ga clusters encapsulated within Silicalite-1 (S-1) catalysts were synthesized using the ligand-protected direct H2 reduction method. The reduced Pt-Ga@S-1-H catalysts comprised restricted ultra-fine Pt-Ga alloys with an average size 0.86–0.95 nm, mainly corresponding to the Pt3 clusters with coordinate number 1.5–2.1. Ga doping significantly improved the catalytic stability, depending on the Ga content, which ranged from 0.02 to 0.27 wt%. As confirmed by the XPS and EXAFS analysis, after the Ga addition, electron transfer occurred between the Pt-Ga alloys and the skeleton oxygen in zeolite, stabilizing the Pt clusters on the zeolite, thereby inhibiting the growth of Pt crystals. During the n-hexane dehydrogenation, the 0.40Pt0.04 Ga@S-1-H catalyst exhibited a hexene selectivity of 87.1 %, achieving a hexene formation rate of 101.4 molhexene∙gPt-1∙h−1 at 550 °C with a WHSV of 90 h−1. After 1000 min of reaction, this best catalyst experienced only slight deactivation with a deactivation constant of 0.066 h−1. The catalytic activity remained almost unchanged after consecutive five cycles of H2 regeneration. DFT calculation using the synchronous structural models showed that the Gibbs free energy changes (−ΔG) for the first three steps of hexane dehydrogenation over the 0.4Pt0.04 Ga@S-1-H catalyst were much lower than those obtained on the 0.4Pt/S-1-H catalyst, suggesting that the introduction of Ga energetically favored the hexane dehydrogenation.
The Ce3+/Ce4+ redox pair induce more oxygen vacancies in the FeTiO3 photocatalyst. The Ce 4f orbital and oxygen vacancy could act as the electron acceptor to capture photoelectrons, inhibiting the ...rapid photocarriers recombination in FeTiO3. Finally, the Ce ions and oxygen vacancies co-synergize to enhance the photocatalytic performance of FeTiO3.
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•(1) The novel oxygen vacancies-rich Ce doped FeTiO3 photocatalysts were successfully designed and synthesized.•(2) The degradation efficiencies for TCH, MB, and BB are up to 97.5 %, 95.4 %, and 84.6 % by the 10 mol% Ce/FeTiO3 photocatalyst, respectively.•(3) DFT calculations were used to investigate the bandgap and density of states of the Ce doped FeTiO3 photocatalyst for the first time.•(4) Ce ions can effectively reduce the photocarriers recombination of FeTiO3.
Doping the iron titanate (FeTiO3) with rare earth element is considered as an effective method of enhancing its photocatalytic performance. In this work, the novel FeTiO3 doped with cerium (Ce) (Ce/FeTiO3) photocatalysts were designed and synthesized using the sol–gel method. The 10 mol% Ce/FeTiO3 photocatalyst displays excellent photocatalytic performance for degrading the tetracycline hydrochloride (TCH), methylene blue (MB) and brilliant blue (BB). The degradation efficiencies are 97.50 % (TCH), 95.40 % (MB), and 84.60 % (BB), respectively, and the degradation rate constants (k) are 3.68, 2.91, and 7.12 times that of pure FeTiO3. Density functional theory (DFT) calculations were used to study the photocatalytic degradation mechanism in depth. The results show that the content of oxygen vacancy is increased and the oxygen vacancy formation energy is significantly increased from 2.25 eV to 6.97 eV after doping the Ce ion, which can provide more active sites to degrade pollutants and enhance the photocatalytic performance of the FeTiO3. Furthermore, the Ce 4f orbital can narrow the bandgap and form the impurity level to capture the photoexcited electron, inhibiting the recombination rate of photocarriers in FeTiO3. This work is expected to provide a valuable insight into the Ce doped FeTiO3 photocatalyst, which is conductive to expanding the practical applications of FeTiO3-based photocatalyst.
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•Mn0.2Cd0.8S formed a stable heterojunction with CeO2.•Mn0.2Cd0.8S/CeO2 achieves efficient photocatalytic HER.•The reaction mechanism of the catalyst is speculated.•The recombination ...of photogenerated carriers was effectively suppressed.•The band gap and state density of catalyst were calculated by DFT.
The Mn0.2Cd0.8S/CeO2 heterojunction is synthesized by means of hydrothermal coupling. Short rod-like Mn0.2Cd0.8S is wrapped in leaf like CeO2 to construct a tight heterointerface, which stimulated the photocatalytic activity to the great extent. Due to the remarkable catalytic and electrochemical properties of Mn0.2Cd0.8S, the CeO2 surface active site is driven. CeO2 has excellent specific surface area, suitable pore volume aperture and Mn0.2Cd0.8S match to optimize the internal interface charge transfer path. At the same time, the heterointerface can coordinate the interface electron flow and promote the H2 reduction ability. The results show that the optimal hydrogen production of Mn0.2Cd0.8S/CeO2 with S-type heterostructure is 291.8 μmol, and the internal lattice and surface morphology of Mn0.2Cd0.8S/CeO2 are not easily damaged due to good catalytic stability. The photocatalytic mechanism of Mn0.2Cd0.8S/CeO2 is studied by finding the short distance interfacial charge transfer path and enriching the photogenerated electrons required for hydrogen evolution.
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•Interfacial engineering between CsSnCl3 and PbSO4/PbCO3 are constructed for defect passivation by DFT.•Sn-O bonds are detected on the interface between CsSnCl3 and PbSO4/PbCO3 ...locking the unsaturated coordination and dangling bonds.•PbCO3/SnCl and PbSO4/SnCl organized satisfactory interfacial energy level structures.•PCE of 15.1946% and 17.3783% were achieved for PSCs devices using PbCO3/SnCl and PbSO4/SnCl as active layers by Solar Design.
Defect passivation of perovskite surface not only reduces non-radiative recombination due to defect trapping charge, but also modulates the interfacial structure and energy levels, making it an effective means of solving the stability problem of perovskite materials. This work provides a passivation strategy for CsSnCl3 perovskite, and the interfacial interactions between CsSnCl3 and the passivation agent (PbSO4 and PbCO3) are explored based on first-principles density functional theory. By introducing PbSO4 and PbCO3 with multifunctional quantum dots, strong Sn-O bonds are formed with unsaturated coordination and dangling bonds on the surface of CsSnCl3. Binding sites of water molecules and impurities would be occupied by these bonds, to achieve surface passivation and dehumidification effects, and significantly improve the optical properties of CsSnCl3. PbCO3/SnCl and PbSO4/SnCl constructed the satisfactory interfacial energy level structures. PbCO3/SnCl exhibited excellent light absorption performance ranging in 0 ∼ 1200 nm. Introducing PbSO4 and PbCO3 reduced the refractive index of CsSnCl3 exhibiting excellent extinction properties. According to the simulation of Solar Design, perovskite solar cells (PSCs) constructed by (PbSO4, PbCO3)/CsSnCl3 as the active layer achieved power conversion efficiencies of 15.1946 % and 17.3783 %, respectively. This work’s research and design results provide a passivation strategy and PSCs design scheme for CsSnCl3 surface defects, which is of great significance for further modification of CsSnCl3 to better apply in photovoltaic field.
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•Mn-CoP porous nanosheets are firstly prepared by a facile in-situ water etching and phosphidation strategy.•Optimized Mn-CoP pre-catalyst shows superb OER performance with an η10 of ...288 mV and high stability.•DFT calculations reveal the crucial role of Mn doping on the enhancement intrinsic OER activity of CoP.
Transition metal phosphides (TMP) show great potential to alternative noble metal based electrocatalysts for oxygen evolution reaction (OER) electrolysis but the still unsatisfactory catalytic activity hinders its practical application. Therefore, it is of much significance to rationally design TMP electrocatalysts for achieving high-efficiency OER. Here, we design Mn-doped cobalt phosphide (Mn-CoP) porous nanosheets for highly active OER through the in-situ metal acetate hydroxide transformation and subsequent phosphidation treatment. Benefiting from synergistic effects of the porous structure, high density of active sites and improved charge-transfer capability, the optimized Mn-CoP serving as a pre-catalyst shows an impressive alkaline OER performance with a low overpotential of 288 mV at the current density of 10 mA cm−2 and high stability. Post-electrolysis characterizations show the conversion from Mn-CoP to vertical Mn-CoOOH hexagonal nanosheets during OER, in which the transformed Mn-CoOOH not only provide extra active sites, but serve as the highly active species. Density functional theory (DFT) calculations reveal that Mn doping can increase the gap states near the Fermi level of active O sites, endowing facilitated deprotonation of OH* to O* and reducing the energy barrier of rate-determining step. This protocol provides a novel insight for the construction of highly efficient TMP water oxidation electrocatalysts.
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•• Effects of halogen and imidazolium on the decomposition of EC were explored.•• The catalytic effects of halogen on polymerization side reactions were revealed.•• The essential ...active site of the composite catalyst was identified.•• Mechanism was proposed by using combined molecular dynamics and DFT calculation.
Coupling of carbon dioxide (CO2) to cyclic carbonates with an epoxide and further into linear carbonates as the indispensable solvents for the lithium-ion batteries has been being one of the hottest topics in transforming CO2 into high value-added chemicals. Nevertheless, the extremely ultrahigh purity requirement for them causes a low efficiency and a modest yield due to the undesired reactions and byproducts occurring in the separation and purification sections. In this work, a novel imidazolium based ionic liquid catalyst system with different anions and cations was studied by a thorough insight into the decomposition reaction of ethylene carbonate (EC), which reveals the synergistic mechanism of the composite catalysts both in section of cyclic carbonate separation from the catalyst for recirculated utilization and purification from the byproducts, and in section of synthesis with high efficiency. Effects of imidazolium cations and halogen anions in the ionic liquid molecule on EC decomposition were investigated by the elaborately designed experiments, thermodynamic estimations, molecular dynamics simulation and DFT assessment. It was found that combining imidazole salts and zinc halides can greatly boost the activity of EC synthesis and decomposition with the effective structure of catalytic center being EMImZnX4. Furthermore, it was indicated that Br- has a higher activity for EC synthesis and its reversed pyrolysis, while Cl- will promote a side reaction of ring-opening polymerization of EC. Finally, a most favorable catalyst composition with ZnBr2 and EMImBr for EC synthesis was achieved with a high efficiency in synthesis and a low tendency to initiate the side reactions in separation section.
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•Catalyst self-separation of ethylene alkoxycarbonylation was enabled using DES.•Prolonged catalyst life was demonstrated with the use of amino acid-based DES.•>99 % ethylene ...conversion and ester selectivity were enabled.•ICP-OES results revealed that 99.2% of Pd was separated.•Catalyst protonation is indispensable for separation and reaction elicitation.
Non-destructive recovery of catalysts is critical for homogeneous catalytic systems with elevated product boiling points, as fragile homogeneous catalysts are potentially deactivated under thermal stress during product separation, and the lack of rational countermeasures to remedy this concern is a major impediment to the widespread application of these reactions. Here, efficient catalyst self-separation of Pd-catalyzed ethylene alkoxycarbonylation with prolonged catalyst life and >99 % selectivity was implemented using a novel cost-effective amino acid-based acidic deep eutectic solvent (DES) as a multifunctional acid co-catalyst. In-depth calculations demonstrate that proton delocalization and hydrogen bonding play a critical role in DES formation. The mechanism of alkoxycarbonylation has been elucidated in terms of energy barrier and substrate complexation, suggesting that the Pd-H mechanism is the preferable path. Computational studies of catalyst separations were performed and the significance of catalyst protonation, which links catalysis and separation, was emphasized.
