Cooperative coupling of hydrogen peroxide (H2O2) photosynthesis with organic pollutant degradation is promising strategy applied in chemical synthesis and environmental protection. Nonetheless, the photocatalytic performance is limited by sluggish photogenerated carrier separation and limited redox potentials. Herein, an S-scheme heterojunction was constructed by assembling the TiO2 nanoparticles and a Schiff-base COF together. The formed S-scheme TiO2/COF heterojunction can efficiently produce H2O2 and degrade Rhodamine B (RhB) synchronously. The S-scheme charge transfer mechanism in TiO2/COF composite is well unveiled by in situ irradiated X-ray photoelectron spectroscopy and DFT calculation. The femtosecond transient absorption spectra reveal the superior charge migration at interface between TiO2 and COF. The designed TiO2/COF composite shows drastically enhanced H2O2 yield of 1326 μmol·g−1·h−1 in RhB solution, and the AQY value of 4.11% under 420 nm monochromatic light irradiation is achieved. Meanwhile, 100% of RhB degraded under light irradiation for 40 min with TiO2/TD COF as photocatalyst. This work exemplifies a promising approach to design COF-based S-scheme heterojunction with ameliorative photocatalytic performance for simultaneous organic pollutants degradation and H2O2 production.

Covalent organic framework(COF)materials are promising photocatalysts because of their fantastic structural and physicochemical features.To enhance photocatalytic performance,numerous metal single atoms(MSA)are loaded on COF to improve molecule adsorption.However,the inherent mechanisms and dominant factors of the heightened adsorption property are not deeply unveiled.Herein,four MSA-COF systems were constructed by severally introducing Fe,Co,Ni,and Cu single atoms in monolayer TpBpy-COF.The effect of various metal atoms modification on the electronic property and O2 adsorption of COF was investigated using density functional theory calculations.The results show that the metal atoms are bonded to the pyridinic N atoms,forming stable MSA-COF configurations.The anchoring of metal atoms reduces the band gap and raises the Fermi level of COF.Moreover,as the atomic number of the metals increases,the d orbitals of the metal atoms gradually move to lower energy levels,manifesting a negative shift of the d-band centers.After metal atoms loading,the weak physical adsorption of O2 on pristine COF is converted to robust chemisorption with the formation of M―Oads bonds and intense electron transfer.Intriguingly,the adsorption energy presents a strong correlation with the d-band centers of the metal atoms.This finding is comprehended from the perspective of electron occupancy in antibonding orbitals in the adsorption systems.This work provides a feasible approach for modifying molecule adsorption on MSA-COF by regulating the d-band centers of metal atoms.

Photocatalytic H 2 O 2 production provides a clean and sustainable strategy for artificial photosynthesis. Herein, an inorganic/organic composite photocatalyst was fabricated by in-situ growth of CdS nanoparticles on the surface of resorcinol-formaldehyde (RF) resin spheres. RF spheres played multiple roles: (i) acting as a substrate for the growth of CdS and constructing a core-shell structure with seamless contact; ( ii ) improving visible light absorption of CdS; ( iii ) forming an S-scheme heterojunction with CdS and promoting the charge separation and transfer. Consequently, under visible light illumination, CdS/RF composite presented remarkably enhanced H 2 O 2 production activity. Its H 2 O 2 yield in 60 min was 801 mu mol L -1 , which was 5.2 and 1.5 times higher than that of RF spheres and CdS hollow spheres, respectively. The charge migration between CdS and RF followed the S-scheme photocatalytic mechanism, which was verified by work function measurement, ex-situ and in-situ irradiated X-ray photoelectron spectroscopy. This work brings a novel insight into designing RF-based inorganic/organic S-scheme heterojunction photocatalysts for efficient H 2 O 2 production. (c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Solar photocatalysis is a promising, green, and sustainable technique for the synthesis of H2O2. In this study, low-dimensional ZnO/ZnIn2S4 S-scheme heterojunction photocatalysts are fabricated using electrostatic spinning and chemical bath deposition methods for the efficient photocatalytic production of H2O2. ZnO nanofibers loaded with 20 wt% ZnIn2S4 exhibit a superior H2O2 production rate of 928 μmol g−1 h−1, which is more than four times higher than that seen in pristine hexagonal phase ZnO and ZnIn2S4. First-principles calculations and in-situ X-ray photoelectron spectroscopy reveal the charge separation and transfer mechanisms in the S-scheme heterojunction. The construction of the S-scheme heterojunction facilitates the spatial separation of charge carriers, and electrons and holes with higher redox abilities are retained. Photoelectrochemical and photoluminescence tests further show that the formation of an S-scheme heterojunction is beneficial for the separation of photoinduced charge carriers. Electrochemical tests and electron paramagnetic resonance measurements indicate that H2O2 production is primarily via a two-step single-electron O2 reduction path. This study provides a new approach for the construction of S-scheme heterojunction materials that can efficiently produce H2O2 under solar irradiation.

High-performance rice husk-derived carbonaceous electrode materials for aqueous zinc-ion hybrid super -capacitors (ZHSCs) were prepared via a simplistically one-step molten salt carbonization process in molten eutectic Na2CO3-K2CO3 at 750, 850 and 950 degrees C. ZHSC assembled by Zn foil as an anode and carbon material prepared at 850 degrees C as a cathode delivers 149.8, 120.1, 108.7, 100.3, 89.3, 80.7 and 69.8F g-1 from 0.2 to 20 A g-1 in 3 mol L-1 Zn(CF3SO3)2 aqueous solution with a rate performance of 47 % capacitance retention. It exhibited energy (power) density with 58.6 Wh kg- 1 (167.8 W kg -1) at 0.2 A g-1 and power (energy) density with 10.0 kW kg- 1 (9.7 Wh kg -1) at 20 A g-1 as well as excellent cyclic stability with 95.8 % capacitance retention and coulombic efficiency of 99.9 % after 3005 charge-discharge cycles at 2 A g-1. The relationship between structure and electrochemical energy storage performance is also discussed with performance depending on the synergistic effect of porous structure, specific surface area, electrical conductivity and het-eroatom doping of rice husk-derived carbon materials.

The conversion from solar energy into storable chemical energy can be achieved through synergistic coupling of photocatalytic H2 production and organic synthesis, during which photogenerated electrons and holes can be simultaneously utilized. Herein, we combined a zirconium-based metal-organic framework, UiO-66-NH2, and CdS nanoparticles (NPs) to form a core-shell structure by a chemical bath method. The step-scheme (S-scheme) heterojunction exhibits both substantially enhanced selective oxidation of benzyl alcohol and efficient H2 generation under light irradiation simultaneously. The electron transfer paths at the S-scheme heterostructure interface were investigated in depth by in situ irradiated X-ray photoelectron spectroscopy. The dynamics of carrier migration at the heterojunction were obtained through femtosecond transient absorption (fs-TA) spectroscopy. Furthermore, the evolution mechanism of benzaldehyde was revealed by in situ diffuse reflectance infrared Fourier transform spectroscopy and electron paramagnetic resonance. This work illustrates the electron transfer mechanism of S-scheme heterojunction by fs-TA spectroscopy and provides new insights into the design of MOF/inorganic composite photocatalysts.

High-performance carbonaceous electrode materials for supercapacitor were prepared via a simple molten salt carbonization of rice husk in molten eutectic Na2CO3-K2CO3 at 850 degrees C. Carbon material with carbonization time of 12 h exhibits an ideal capacitive property, benefitting from the synergistic effect of hierarchically porous structure with high SSA and mesopore/micropore ratio, oxygen doping and excellent electrical conductivity. In a three-electrode system, it exhibits specific capacitance of 117.0-163.1 F g-1 at current density of 20-0.2 A g-1 with rate performance of 72 % capacitance retention, energy (power) density of 22.6 Wh kg-1 (99.9 W kg -1) at 0.2 A g-1 and power (energy) density of 9.5 kW kg-1 (14.5 Wh kg -1) at 20 A g-1. When the carbon material was assembled into a symmetrical supercapacitor, it exhibits specific capacitance of 103.4-148.3 F g-1 at current density of 20-0.2 A g-1 with rate performance of 70 % capacitance retention, energy (power) density of 5.1 Wh kg-1 (49.9 W kg -1) at 0.2 A g-1 and power (energy) density of 4.3 kW kg-1 (2.7 Wh kg -1) at 20 A g-1, as well as excellent cyclic stability with 85 % capacitance retention and the coulombic efficiency close to 100 % after 6000 charge-discharge cycles at 1 A g-1. The dependence of hierarchically porous structure on capacitive performance is also discussed.

Bi 2 O 3 /BiOI step-scheme(S-scheme) heterojunction photocatalyst was synthesized by green calcination method, its degradation ability of methylene blue was investigated, and the photocatalytic performance of the Bi 2 O 3 /BiOI heterojunction, Bi 2 O 3 and BiOI was compared. The structure and morphology of the samples were characterized by X- ray diffraction(XRD), field emission scanning electron microscopy (FESEM), and UV-vis diffuse reflection spectrum (UV-vis DRS). The degradation rate of methylene blue was analysised by spectrophotometry, and the calculation result showed that the degradation rate of methylene blue was 97.8% in 150 minutes. The first order kinetic rate constant of 10%Bi 2 O 3 /BiOI is 0.021 8 min −1 , which are 2.37 and 2.68 times of BiOI(0.009 18 min −1 ) and Bi 2 O 3 (0.008 03 min −1 ) respectively. The calculation result shows that the work function of Bi 2 O 3 and BiOI are 3.0 eV and 6.0 eV, respectively, by density functional theory(DFT). When this S-scheme heterojunction is used as a photocatalyst, the weaker electrons in the conduction band of BiOI will be combined with the weaker holes in the Bi 2 O 3 valence band under combined effect with built-in electric field and band bending, which will retain stronger photoelectrons and holes between Bi 2 O 3 and BiOI. This may be the internal reason for the efficient degradation of tetracycline by Bi 2 O 3 /BiOI S-scheme heterostructures.

Solar‐driven semiconductor photocatalysis shows great potential to solve growing energy and environmental crises. Electrospun TiO 2 nanofibers (NFs) attract attention due to their chemical stability, nontoxicity, cheapness, large specific surface area, and porous structures. The unique unwoven nanofibrous network facilitates mass transportation compared with bulk materials. Electrospun TiO 2 NFs are an ideal substrate for growing secondary nanostructures and constructing heterojunction photocatalysts. The hybrid heterojunctions show enhanced electron–hole separation, improved light absorption, effective activation of reactants, and therefore increased photocatalytic performance. Herein, the electrospinning principle and preparing tactics of electrospun TiO 2 fibrous nanostructures including solid, hollow, and core/shell NFs are first described. The construction strategies of electrospun TiO 2 ‐based heterojunctions by loading electron or hole cocatalysts and hybridizing secondary semiconductors to engineer catalytic active sites and steer charge carrier separation are outlined. Dopant‐induced increased light absorption and enhanced charge transfer of TiO 2 NFs are discussed. Further, the applications of electrospun TiO 2 ‐based photocatalysts for solar‐to‐chemical conversion and environmental remediation are elucidated. Finally, the challenges and perspectives for the development of electrospun TiO 2 ‐based photocatalysts are underlined, which deepen a systematic understanding of the design and fabrication of more efficient electrospun NFs in the future.

以绿色焙烧方法制备梯形异质结复合材料Bi2 O3/BiOI,将复合材料Bi2 O3/BiOI用于抗生素生产废水中四环素的降解,并与纯的Bi2 O3与BiOI的降解效果进行对比.以X射线衍射(XRD)、X射线光电子能谱(XPS)对Bi2 O3/BiOI样品物相组成和形貌进行表征分析,采用分光光度法测试并计算Bi2 O3/BiOI样品降解四环素,结果显示:降解率为92.4％,一级动力学常数为0.01859 min-1.密度泛函理论计算显示,Bi2 O3与BiOI的功函数分别为3.0、6.0 eV.梯形异质结复合材料Bi2 O3/BiOI在光催化反应时,在内建电场和能带弯曲的共同作用下,BiOI中导带上还原能力较弱的电子将与Bi2 O3价带中氧化能力较弱的空穴部分复合,从而保留较强还原以及氧化能力的光生电子和空穴,这可能是梯形异质结复合材料Bi2 O3/BiOI具有较高光催化活性的原因.

Artificial photosynthesis by CO2 photoreduction is an ideal channel for mitigating the greenhouse effect and energy crises. Nevertheless, its efficiency is still low due to severe charge recombination and sluggish kinetics. Herein, an S‐scheme BiOBr/NiO heterojunction, composed of two kinds of p‐type semiconductors, exhibits enhanced CO2 photoreduction activity. Enhanced light absorption and specific surface area are attributable to NiO nanosheets with hierarchical porous structures. Results from in situ irradiated X‐ray photoelectron spectroscopy and work function calculation manifest that the photoexcited electrons transfer from BiOBr to NiO via the S‐scheme mechanism. And charge separation and a strong redox ability are simultaneously realized. In situ diffuse reflectance infrared Fourier transform spectra unveil complex intermediates in CO2 photoreduction. This work presents a novel understanding for the CO2 photoreduction mechanism of S‐scheme heterojunctions built by p‐type semiconductors by integrating in situ monitoring techniques with density functional theory calculation.

Photocatalytic reduction of CO2 to hydrocarbon compounds is a promising method for addressing energy shortages and environmental pollution. Considerable efforts have been devoted to exploring valid strategies to enhance photocatalytic efficiency. Among various modification methods, the hybridization of different photocatalysts is effective for addressing the shortcomings of a single photocatalyst and enhancing its CO2 reduction performance. In addition, metal-free materials such as g-C3N4 and black phosphorus (BP) are attractive because of their unique structures and electronic properties. Many experimental results have verified the superior photocatalytic activity of a BP/g-C3N4 composite. However, theoretical understanding of the intrinsic mechanism of the activity enhancement is still lacking. Herein, the geometric structures, optical absorption, electronic properties, and CO2 reduction reaction processes of 2D/2D BP/g-C3N4 composite models are investigated using density functional theory calculations. The composite model consists of a monolayer of BP and a tri-s-triazine-based monolayer of g-C3N4. Based on the calculated work function, it is inferred that electrons transfer from g-C3N4 to BP owing to the higher Fermi level of g-C3N4 compared with that of BP. Furthermore, the charge density difference suggests the formation of a built-in electric field at the interface, which is conducive to the separation of photogenerated electron-hole pairs. The optical absorption coefficient demonstrates that the light absorption of the composite is significantly higher than that of its singlecomponent counterpart. Integrated analysis of the band edge potential and interfacial electronic interaction indicates that the migration of photogenerated charge carriers in the BP/g-C3N4 hybrid follows the S-scheme photocatalytic mechanism. Under visible-light irradiation, the photogenerated electrons on BP recombine with the photogenerated holes on g-C3N4, leaving photogenerated electrons and holes in the conduction band of g-C3N4 and the valence band of BP, respectively. Compared with pristine g-C3N4, this S-scheme heterojunction allows efficient separation of photogenerated charge carriers while effectively preserving strong redox abilities. Additionally, the possible reaction path for CO2 reduction on g-C3N4 and BP/g-C3N4 is discussed by computing the free energy of each step. It was found that CO2 reduction on the composite occurs most readily on the g-C3N4 side. The reaction path on the composite is different from that on g-C3N4. The heterojunction reduces the maximum energy barrier for CO2 reduction from 1.48 to 1.22 eV, following the optimal reaction path. Consequently, the BP/g-C3N4 heterojunction is theoretically proven to be an excellent CO2 reduction photocatalyst. This work is helpful for understanding the effect of BP modification on the photocatalytic activity of g-C3N4. It also provides a theoretical basis for the design of other high-performance CO2 reduction photocatalysts.

采用水热法合成异质结复合光催化材料BiOI/BiOBr,探究其对罗丹明B的降解能力,并与纯的BiOBr以及BiOI的降解情况进行比较.通过X射线衍射XRD、场发射扫描电子显微镜FESEM、紫外-可见漫反射光谱DRS以及稳态、瞬态荧光光谱PL等表征方法对合成的异质结复合光催化剂BiOI/BiOBr样品进行了结构、形貌、光学性质的表征.采用分光光度法分析罗丹明B的降解率,结果显示,BiOI/BiOBr异质结光催化材料对100 mg/L的罗丹明B有很好的降解能力,在40 min内对罗丹明B的降解率为100％,明显高于纯的BiOBr(80％)和BiOI(72％);其一级动力学速率常数为0.1028 min-1,分别为BiOBr(0.0403 min-1)和BiOI(0.0344 min-1)的2.6倍和3倍.这种异质结光催化剂不仅可以有效促进光生电荷分离而且可以保持复合材料的强氧化还原能力,这可能是BiOI/BiOBr异质结高效降解罗丹明B的内在原因.

Photocatalytic CO2 conversion into solar fuels has been a promising strategy to utilize abundant solar energy and alleviate greenhouse effect. Herein, a series of polydopamine-modified TiO2 (TiO2@PDA) hollow spheres were fabricated by in situ self-polymerization of dopamine to systematically investigate the effect of PDA wrapping on the photocatalytic CO2 reduction activities of TiO2. Among all TiO2@PDA composite photocatalysts, the highest value of methane yield (1.50 mu mol h(-1) g(-1)) was achieved with 0.5 % PDA, which was 5 times than that of pure TiO2 (0.30 mu mol h(-1) g(-1)). The improvement of photocatalytic activity and methane selectivity was ascribed to the enhanced light absorption, promoted CO2 adsorption capacity, increased reduction power of photogenerated electrons, as well as efficient separation and transfer of photogenerated charge carriers induced by the S-scheme heterojunction between TiO2 and PDA. This work provides a facile surface modification method with cost-effective polymer materials in photocatalytic CO2 conversion.

Single photocatalysts usually exhibit unsatisfactory performance due to the serious recombination of photogenerated electron‒hole pairs. Combining two photocatalysts to construct S-scheme heterojunction could solve this problem. In S-scheme mechanism, the interfacial built-in electric field (IEF) provides a vital driving force for efficient charge separation. Modifying the IEF is a feasible strategy to further improve the photocatalytic activity. Herein, a novel idea of tuning the strength of IEF in 2D/2D graphitic carbon nitride (g-C3N4)/MS2 (M = Sn, Zr) S-scheme heterojunctions by nonmetal doping was developed by employing density functional theory calculation. Three nonmetal elements (O, P, and S) were severally introduced into g-C3N4/MS2 composites. Charge density difference suggested that O and S doping led to increased interfacial electron transfer, while P doping had minimal influence. As expected, the calculated field strength of O- and S-doped g-C3N4/MS2 composites was significantly larger than that of pristine and P-doped g-C3N4/MS2 composites. Therefore, O and S doping endowed g-C3N4/MS2 S-scheme heterojunctions with enhanced IEF and more thorough charge transfer. Correspondingly, the experimentally synthesized O-C3N4/SnS2 composite exhibited better photocatalytic H2-production activity than g-C3N4/SnS2 composite. This work proposed an original idea of employing proper nonmetal doping to magnify the advantage of S-scheme heterojunction in accelerating charge separation.

Intimate interfacial contact between semiconductor photocatalysts and cocatalysts is important for the transfer and separation of photogenerated charge carriers. Herein, few-layer graphene, as an efficient cocatalyst, was in situ deposited on the surface of ZnO. The composite demonstrated improved photocatalytic CO2 reduction performance than pristine ZnO, ascribing to the intimate interfacial contact and Schottky junction between ZnO and graphene. Meanwhile, photothermal effect of graphene and pi-pi conjugation interaction between graphene and CO2 molecules also contributed to the performance enhancement. This work not only provides a feasible approach for the in-situ growth of graphene, but also develops an efficient photocatalyst for CO2 reduction.

Metal–organic framework of MIL‐53(Al) (Al(OH)‐[O2C‐C6H4‐CO2]) with exceptional thermal stability (as high as ≈550 °C in dynamic conditions) are synthesized via a solvothermal method, which serve as a porous host matrix of Co‐based catalysts for Fischer–Tropsch synthesis (FTS). MIL‐53(Al) shows large micropores and lattice dynamic flexibility, which make this material a promising support for active cobalt species. The as‐synthesized Co/MIL‐53(Al) catalysts with different cobalt loadings are characterized by powder X‐ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), X‐ray photoelectron spectroscopy (XPS), thermogravimetry (TG), Fourier‐transform infrared (FT‐IR) spectroscopy, and temperature programmed reduction. The results show that the immobilization of Co nanoparticles on the MIL‐53(Al) support could be beneficial to obtain novel effective catalysts for FTS. Moreover, compared with the Co/γ‐Al2O3 catalyst of the same cobalt loading, the catalytic performance of Co/MIL‐53(Al) catalyst shows higher FTS activity. Interestingly, the gasoline selectivity over the Co/MIL‐53(Al) catalyst is much higher than that of the Co/γ‐Al2O3 catalyst, close to the optimal value for maximum gasoline and diesel production.

I-doped Bi4O5Br2 (I-Bi4O5Br2) nanosheets have been synthesized by a facile anion exchange method at room temperature. The formed I-Bi4O5Br2 products have been characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–Vis diffuse reflectance and X-ray photoelectron spectroscopy. I-Bi4O5Br2 nanosheets with good crystallinity and a band gap energy of 2.36 eV have stronger absorption in the visible-light region. Compared to pure Bi4O5Br2, I-Bi4O5Br2 photocatalysts showed better performance for methyl orange degradation under visible light irradiation, which could be ascribed to more visible light harvest and more effective separation of photo-generated carriers.

The novel 2D-2D p-n heterojunction BiOBr/Bi12O15Cl6 composites were formed by loading BiOBr nanosheets on the the surface of Bi(12)O(15)Cl(6 )nanosheets. The samples were characterized by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy dispersive spectrometer, X-ray diffraction and X-ray photoelectron spectroscopy. The obtained BiOBr/Bi12O15Cl6 p-n heterojunction composites exhibited the superior photocatalytic activity for the degrading methyl orange under visible light irradiation as compared with Bi(12)O(15)Cl(6 )and BiOBr, which should be mainly attributed to the formation of p-n heterojunction between Bi12O15Cl6 and BiOBr, resulting in the higher quantum efficiency and stronger photocatalysis activity.

Two zinc(II) metal-organic coordination polymers, namely [ZnL(BIB)]n·n(EtOH) (1) and [ZnL(BIB)]n (2) (where H2L=(fluorene-9,9-diyl)di- propanoic acid and BIB=1,3-bis(imidazol-1-yl)butane) have been synthesized using the same starting reactants but different solvent medium. Both the complexes have been structurally characterized. Compound (1) exhibits a two-dimensional (2D) coordination framework. However, complex (2) is composed of 2D structure which is further resulted in a 3-fold interpenetrating structure. Thermogravimetric analyses (TGA) and luminescent properties of these two complexes have been discussed.