Oxygen Vacancy Engineering and Constructing Built-In Electric Field in Fe-g-C3N4/Bi2MoO6 Z-Scheme Heterojunction for Boosting Photo-Fenton Catalytic Degradation Performance of Tetracycline.

A novel Fe-g-C3N4/Bi2MoO6 (FCNB) Z-scheme heterojunction enriched with oxygen vacancy is constructed and employed for the photo-Fenton degradation of tetracycline (TC). The 2% FCNB demonstrates prominent catalytic performance and mineralization efficiency for TC wastewater, showing activity of 8.20 times greater than that of pure photocatalytic technology. Density-functional theory (DFT) calculations and degradation experiments confirm that the formation of Fe-N4 sites induces spin-polarization in the material, and the difference in Fermi energy levels results in the formation of built-in electric field at the contact interface, which facilitates the continuous generation and migration of photogenerated carriers to address the issue of insufficient cycling power of Fe (III)/Fe (II).The reactive radicals persistently target the extremely reactive sites anticipated by the Fukui function, causing the mineralization of TC molecules into "non-toxic" compounds through processes of hydroxylation, demethylation, and deamidation. This work holds significant importance in the domain of eliminating organic pollutants from water.

Cobalt nanoparticles intercalation coupled with tellurium-doping MXene for efficient electrocatalytic water splitting.

Nowadays, the inherent re-stacking nature and weak d-p hybridization orbital interactions within MXene remains significant challenges in the field of electrocatalytic water splitting, leading to unsatisfactory electrocatalytic activity and cycling stability. Herein, this work aims to address these challenges and improve electrocatalytic performance by utilizing cobalt nanoparticles intercalation coupled with enhanced π-donation effect. Specifically, cobalt nanoparticles are integrated into V2C MXene nanosheets to mitigate the re-stacking issue. Meanwhile, a notable charge redistribution from cobalt to vanadium elevates orbital levels, reduces π*-antibonding orbital occupancy and alleviates Jahn-Teller distortion. Doping with tellurium induces localized electric field rearrangement resulting from the changes in electron cloud density. As a result, Co-V2C MXene-Te acquires desirable activity for hydrogen evolution reaction and oxygen evolution reaction with the overpotential of 80.8 mV and 287.7 mV, respectively, at the current density of -10 mA cm-2 and 10 mA cm-2. The overall water splitting device achieves an impressive low cell voltage requirement of 1.51 V to obtain 10 mA cm-2. Overall, this work could offer a promising solution when facing the re-stacking issue and weak d-p hybridization orbital interactions of MXene, furnishing a high-performance electrocatalyst with favorable electrocatalytic activity and cycling stability.

Iron Active Center Coordination Reconstruction in Iron Carbide Modified on Porous Carbon for Superior Overall Water Splitting.

In this work, a novel liquid nitrogen quenching strategy is engineered to fulfill iron active center coordination reconstruction within iron carbide (Fe3C) modified on biomass-derived nitrogen-doped porous carbon (NC) for initiating rapid hydrogen and oxygen evolution, where the chrysanthemum tea (elm seeds, corn leaves, and shaddock peel, etc.) is treated as biomass carbon source within Fe3C and NC. Moreover, the original thermodynamic stability is changed through the corresponding force generated by liquid nitrogen quenching and the phase transformation is induced with rich carbon vacancies with the increasing instantaneous temperature drop amplitude. Noteworthy, the optimizing intermediate absorption/desorption is achieved by new phases, Fe coordination, and carbon vacancies. The Fe3C/NC-550 (550 refers to quenching temperature) demonstrates outstanding overpotential for hydrogen evolution reaction (26.3 mV at -10 mA cm-2) and oxygen evolution reaction (281.4 mV at 10 mA cm-2), favorable overall water splitting activity (1.57 V at 10 mA cm-2). Density functional theory (DFT) calculations further confirm that liquid nitrogen quenching treatment can enhance the intrinsic electrocatalytic activity efficiently by optimizing the adsorption free energy of reaction intermediates. Overall, the above results authenticate that liquid nitrogen quenching strategy open up new possibilities for obtaining highly active electrocatalysts for the new generation of green energy conversion systems.

Strain Engineering for Electrocatalytic Overall Water Splitting.

Strain engineering is a novel method that can achieve superior performance for different applications. The lattice strain can affect the performance of electrochemical catalysts by changing the binding energy between the surface-active sites and intermediates and can be affected by the thickness, surface defects and composition of the materials. In this review, we summarized the basic principle, characterization method, introduction strategy and application direction of lattice strain. The reactions on hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are focused. Finally, the present challenges are summarized, and suggestions for the future development of lattice strain in electrocatalytic overall water splitting are put forward.

Double-Shelled Porous g-C3 N4 Nanotubes Modified with Amorphous Cu-Doped FeOOH Nanoclusters as 0D/3D Non-Homogeneous Photo-Fenton Catalysts for Effective Removal of Organic Dyes.

Graphite phased carbon nitride (g-C3 N4 ) has attracted extensive attention attributed to its non-toxic nature, remarkable physical-chemical stability, and visible light response properties. Nevertheless, the pristine g-C3 N4 suffers from the rapid photogenerated carrier recombination and unfavorable specific surface area, which greatly limit its catalytic performance. Herein, 0D/3D Cu-FeOOH/TCN composites are constructed as photo-Fenton catalysts by assembling amorphous Cu-FeOOH clusters on 3D double-shelled porous tubular g-C3 N4 (TCN) fabricated through one-step calcination. Combined density functional theory (DFT) calculations, the synergistic effect between Cu and Fe species could facilitate the adsorption and activation of H2 O2 , and the separation and transfer of photogenerated charges effectively. Thus, Cu-FeOOH/TCN composites acquire a high removal efficiency of 97.8%, the mineralization rate of 85.5% and a first-order rate constant k = 0.0507 min-1 for methyl orange (MO) (40 mg L-1 ) in photo-Fenton reaction system, which is nearly 10 times and 21 times higher than those of FeOOH/TCN (k = 0.0047 min-1 ) and TCN (k = 0.0024 min-1 ), respectively, indicating its universal applicability and desirable cyclic stability. Overall, this work furnishes a novel strategy for developing heterogeneous photo-Fenton catalysts based on g-C3 N4 nanotubes for practical wastewater treatment.

Novel Strain Engineering Combined with a Microscopic Pore Synergistic Modulated Strategy for Designing Lattice Tensile-Strained Porous V2C-MXene for High-Performance Overall Water Splitting.

Transition metal carbon/nitride (MXene) holds immense potential as an innovative electrocatalyst for enhancing the overall water splitting properties. Nevertheless, the re-stacking nature induced by van der Waals force remains a significant challenge. In this work, the lattice tensile-strained porous V2C-MXene (named as TS(24)-P(50)-V2C) is successfully constructed via the rapid spray freezing method and the following hydrothermal treatment. Besides, the influence of lattice strain degree and microscopic pores on the catalytic ability is reviewed and explored systematically. The lattice tensile strain within V2C-MXene could widen the interlayer spacing and accelerate the ion transfer. The microscopic pores could change the ion transmission path and shorten the migration distance. As a consequence, the obtained TS(24)-P(50)-V2C shows extraordinary hydrogen evolution reaction and oxygen evolution reaction activity with the overpotential of 154 and 269 mV, respectively, at the current density of 10 mA/cm2, which is quite remarkable compared to the MXene-based electrocatalysts. Moreover, the overall water splitting device assembled using TS(24)-P(50)-V2C as both anode and cathode demonstrates a low cell voltage requirement of 1.57 V to obtain 10 mA/cm2. Overall, the implementation of this work could offer an exciting avenue to overcome the re-stacking issue of V2C-MXene, affording a high-efficiency electrocatalyst with superior catalytic activity and desirable reaction kinetics.

Liquid nitrogen quenching inducing lattice tensile strain to endow nitrogen/fluorine co-doping Fe3O4 nanocubes assembled on porous carbon with optimizing hydrogen evolution reaction.

In this work, the lattice tensile strain of nitrogen/fluorine co-doping ferroferric oxide (Fe3O4) nanocubes assembled on chrysanthemum tea-derived porous carbon is induced through a novel liquid nitrogen quenching treatment (named as TS-NF-FO/PCX-Y, TS: Tensile strain, NF: Nitrogen/Fluorine co-doping, FO: Fe3O4, PC: Porous carbon, X: The weight ratio of KOH/carbon, Y: The adding amount of porous carbon). Besides, the electrocatalytic activity influenced by the adding amount of porous carbon, the type of dopant, and the introduction of lattice tensile strain is systematically studied and explored. The interconnected porous carbon could improve electrical conductivity and prevent Fe3O4 nanocubes from aggregating. The induced nitrogen/fluorine could cause extrinsic defects and tailor the intrinsic electron state of the host materials. Lattice tensile strain could tailor the surface electronic structure of Fe3O4 via changing the dispersion of surface atoms and their bond lengths. Impressively, the designed TS-NF-FO/PC5-0.25 delivers a low overpotential of 207.3 ± 0.4 mV at 10 mA/cm2 and demonstrates desirable reaction dynamics. Density functional theory calculations illustrate that the electron structure and hydrogen adsorption free energy (ΔG*H) are optimized by the synergistic effect among porous carbon, nitrogen/fluorine co-doping and lattice tensile strain, thus promoting hydrogen evolution reaction (HER) catalytic activity. Overall, this work paves the way to unravel the enhancement mechanism of HER on transition metal oxide-based materials by electronic structure and phase composition modulation strategy.

g-C3N4-wrapped nickel doped zinc oxide/carbon core-double shell microspheres for high-performance photocatalytic hydrogen production.

The development of efficient heterojunctions with enhanced photocatalytic properties is considered a promising approach for photocatalytic hydrogen production. In this study, graphitic carbon nitride (g-C3N4)-wrapped nickel-doped zinc oxide/carbon (Ni-ZnO@C/g-C3N4) core-double shell heterojunctions with unique core-double shell structures were employed as efficient photocatalysts through an innovative approach. Ni doping can enhance the intensity and range of visible light absorption in ZnO, and the carbon core coupled with the hollow double-shell structure can accelerate the charge transfer rate and improve the photon utilization efficiency. Meanwhile, the construction of the Z-scheme heterojunction extended the electron-hole pair transport path. In addition, the Z-scheme charge-transfer mechanism of Ni-ZnO@C/g-C3N4 under simulated sunlight was verified by photoluminescence (PL) and electron spin resonance (ESR) experiments. As a result, the obtained photocatalyst acquired a high hydrogen evolution rate of 336.08 µmol g-1h-1, which is 36.49 times higher than that of pristine ZnO. Overall, this work may provide a pathway for the construction of highly efficient photocatalysts with unique core-double shell structures.

Structure-designed synthesis of hollow/porous cobalt sulfide/phosphide based materials for optimizing supercapacitor storage properties and hydrogen evolution reaction.

Cobalt-based transition metal phosphides/sulfides have been viewed as promising candidates for supercapacitor (SCs) and hydrogen evolution reaction (HER) featured with their intrinsic merits. Nevertheless, the sluggish reaction kinetics and drastic volume expansion upon electrochemical process hinder their commercial application. In this work, the hollow/porous cobalt sulfide/phosphide based nanocuboids (C-CoP4 and CoS2 HNs) with superior specific surface area are achieved by employing a novel chemical etching-phosphatization/sulfuration strategy. The hollow/porous structure could offer rich active sites and shorten electrons/ions diffusion length. In virtue of their structural advantage, the obtained C-CoP4 and CoS2 HNs perform superior specific capacitance, fast charge/discharge rate and beneficial cycling stability. The advanced asymmetrical supercapacitors assembled by C-CoP4 and CoS2 HNs deliver exceptional energy density, respectively. Furthermore, when employed as hydrogen evolution reaction electrocatalysts, C-CoP4 and CoS2 HNs yield favorable electrocatalytic activity. These findings shed fundamental insight on the design of dual-functional transition metal phosphide/sulfide based materials for optimizing hydrogen evolution reaction and supercapacitor storage properties.

Synthesis of 3D flower-like structured Gd/TiO2@rGO nanocomposites via a hydrothermal method with enhanced visible-light photocatalytic activity.

In this study, novel Gd/TiO2@rGO (GTR) nanocomposites with high photocatalytic performance were fabricated via a one-pot solvothermal approach. During the preparation step, graphene oxide (GO) was reduced to reduced graphene oxide (rGO), and subsequently, on the surfaces of which anatase TiO2 doped with Gd metal was grown in situ with a 3D petal-like structure. Gd doping into the classical TiO2@rGO system efficiently expands the absorption range of light, improves the separation of photogenerated electrons, and increases the photocatalytic reaction sites. The specific surface areas, morphological structures, and valence and conduction bands of the obtained GTR nanocomposites were analyzed and correlated with their enhanced photocatalytic performances for the degradation of an aqueous RhB solution. The experimental results indicated that the best performance was achieved with the 3% GTR composite, which exhibited the highest photoelectrocatalytic activity because of two aspects: the rapid separation of electrons and holes, and improvement in adsorption capacity. As compared with pure TiO2, the GTR composites demonstrated enhanced photoactivity due to synergetic effects between the effective photo-induced electron transfer from TiO2 to the surface of the rGO acceptor through interfacial interactions and the variation of structure and electrons under the adoption of Gd.

Synthesis and photocatalytic properties of visible-light-responsive, three-dimensional, flower-like La-TiO2/g-C3N4 heterojunction composites.

We prepared a new three-dimensional, flower-like La-TiO2/g-C3N4 (LaTiCN) heterojunction photocatalyst using a solvothermal method. Analysis and characterization were performed by conducting scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform-infrared spectroscopy, ultraviolet-visible spectrophotometry, and nitrogen adsorption and desorption. The prepared g-C3N4 nanosheets could reach 100 nm in size and covered the TiO2 surface. A tightly bound interface formed between the g-C3N4 and TiO2, speeding up the effective transfer of photo-induced electrons. In addition, the incorporation of La3+ reduced the electron-hole recombination efficiency. Consequently, the prepared La-TiO2/g-C3N4 composite material exhibited better visible-light catalytic activity than pure TiO2.

Photocatalytic Performance of a Nd-SiO2-TiO2 Nanocomposite for Degradation of Rhodamine B Dye Wastewater.

The photocatalytic performance of a novel Nd-SiO2-TiO2 nanocomposite catalyst prepared by a sol-gel method was examined in the degradation of Rhodamine B (RhB), a notorious organic compound present in dye wastewaters. The prepared samples were characterized by low-temperature N2 adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (DRS). Fourier-transform infrared (FT-IR) spectroscopic analysis indicated the enhanced chemical bonding of O--Ti and O--Ti--O with introduction of Nd and SiO2 dopant species into TiO2. The Nd-SiO2-TiO2 nanocomposite was found to exhibit a much higher photo- catalytic activity toward the decomposition of RhB under both UV and visible light irradiation as compared to a commercial TiO2 photocatalyst. The photodegradation efficiency of RhB (5 mg/L) was greater than 93% under visible light irradiation after 90 min. Addition of SiO2 was shown to not only inhibit crystal growth and TiO2 anatase-to-rutile phase transformation, but also enhance the adsorption of organic compounds. Nd doping has been suggested for slowing down the radiative recombination of photo-generated electrons and holes in TiO2, extending the photocatalyst light response to the visible region. The synergetic effects between Nd-SiO2 and TiO2 are described; the prepared Nd-SiO2-TiO2 represents a noteworthy contribution to the study of pollutant degradation in dye wastewaters.

Photocatalytic degradation of dyestuff wastewater with Zn(2+)-TiO2-SiO2 nanocomposite.

A novel photocatalyst of Zn(2+)-TiO2-SiO2 nanocomposite has been prepared by a sol-gel method, which is used for the degradation of Rhodamine B (RhB) and Congo red (CR) as the probe dyestuff that are notorious organic compounds present in dyes wastewater. The prepared samples are characterized by low temperature N2 adsorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy (DRS) and Fourier transformed infrared spectroscopy (FT-IR). It is found that the nanocomposite of Zn(2+)-TiO2-SiO2 exhibits much higher photocatalytic activity under both UV light and visible light irradiation as compared with Degussa P25, Zn(2+)-TiO2 and SiO2-TiO2. The photodegradation efficiencies of RhB (5 mg/L) and CR (10 mg/L) can reach above 90% and 83% for 1.5 h visible light irradiation, respectively. Synergetic effect between Zn(2+)-SiO2-doping not only inhibit the crystal growth and anatase-to-rutile transformation of TiO2 nanocatalyst, but also extend the light response to the visible region, which provides a good way and material in the degradation field of dyes wastewater.

Nanocomposite of Cu-TiO2-SiO2 with high photoactive performance for degradation of rhodamine B dye in aqueous wastewater.

The nanocomposite of Cu-TiO2-SiO2 photocatalyst have been prepared by a sol-gel method, which is used for the degradation of Rhodamine B (RB) as a probe that is notorious organic compound present in dyes wastewater. Morphological and structural characteristics of the Cu-TiO2-SiO2 nanocomposite were studied with low temperature N2 adsorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectroscopy (DRS). The Fourier transformed infrared spectroscopy (FT-IR) analysis shows the enhanced chemical bonding of O-Ti and O-Ti-O after the composition of Cu and SiO2 species into TiO2. It is found that the Cu-TiO2-SiO2 nanocomposite exhibits much higher photocatalytic activity under both UV light and visible light irradiation as compared with that over commercial titania (Degussa P25) toward the dyes wastewater containing RB. The photodegradation rate of RB (5 mg/L) can reach above 95.0% under sunlight after 3 h. The addition of SiO2 not only inhibites the crystal growth and anatase-to-rutile transformation of TiO2 nanocatalyst, but also enhances the adsorption of organic compounds. Cu-doping extends the light response to the visible region. Synergetic effects between Cu-SiO2 and TiO2 have been investigated, which provides a good way and material in the degradation field of dyes wastewater.