Efficient Visible Light Catalyst Research Articles

G-C3N4 modified with non-precious metal Al with LSPR as an efficient visible light catalyst.

The issue of water pollution has emerged as a formidable challenge, prompting a pressing need for solutions. The utilization of metal nanoparticles with surface plasmon resonance and semiconductor composite photocatalysts is regarded as a highly effective approach to solve this problem. g-C3N4 is an effective catalyst for the degradation of organic pollutants. Its photocatalytic performance is usually enhanced by the use of the noble metal Au Ag. However, the high cost of these materials limits their application. In this study, we present the synthesis of Al NPs/g-C3N4 nanocomposites using the bridging effect of ligands. The characterized of transmission electron microscopy (TEM), X-ray diffractometer (XRD) and ultraviolet-visible spectroscopy (UV-Vis) proved that Al NPs/g-C3N4 with a wider light absorption range were successfully synthesized. The effects of ligands, (glutathione (GSH), glutamic acid (GAG), and cysteine (CYS)), Al diameter (40 to 200 nm) and the ratio of Al to g-C3N4 (1:1 to 5:1) on the photocatalytic degradation of methylene blue (MB) by Al NPs/g-C3N4 were also evaluated. The results showed that the optimum degradation efficiency of Al NPs/g-C3N4 for MB at 5 mg/L reached 100% within 60 min, which was 11 times higher than that of pure g-C3N4. The principal analysis of Al enhancing the photocatalytic performance of g-C3N4 was studied through transient photocurrent spectroscopy (TPC), electrochemical impedance spectroscopy (EIS), and steady-state transient fluorescence spectroscopy (PL). The results confirmed that hot carriers generated by localized surface plasmon resonance (LSPR) of Al nanoparticles increase the carrier concentration. In addition, the Schottky barrier generated by Al and g-C3N4 could also improve the carrier separation rate and increase the carrier lifetime. This work is expected to solve the problem of organic wastewater treatment and lay the foundation for subsequent research on photocatalysis.

Au decorated chemically exfoliated g-C3N4 as highly efficient visible light catalyst for hydrogen production

The demand for photocatalytic hydrogen production through water splitting is continuously increasing as the world is seeking cleaner and sustainable energy solutions. Herein, we report a comparative study of the as-fabricated Bulk g-C3N4 (BCN), chemically exfoliated g-C3N4 (ECN) and Au-decorated chemically exfoliated g-C3N4 (Au/ECN) photocatalysts for visible light-driven catalytic hydrogen production. To understand the structural, morphological, chemical, and electronic properties of the as-fabricated photocatalysts, XRD, TEM, Raman, PL, XPS, FTIR, UV and EPR analysis was performed. The as-prepared Au/ECN photocatalyst revealed exceptional visible light catalytic performance by producing 410 μmol·g−1 of hydrogen, which is 27.3- and 9.3-fold enhanced compared to those of the CN (15 μmol·g−1) and ECN (44 μmol·g−1) photocatalysts, respectively. This improved visible light-driven catalytic performance of the Au/ECN photocatalyst for hydrogen production is due to the enhanced specific surface area via the chemically exfoliated layered sheets, promoted light absorption due to the decrease in band gap via the effect of surface plasmon resonance attributable to decorated Au nanoparticles, and efficient separation of charge carriers at the interfacial contact. The photocatalytic recyclable experiments indicate excellent stability of the Au/ECN photocatalyst for H2 evolution. These findings reveal the effect of chemical exfoliation and Au decorating on the catalytic efficiency of g-C3N4-based photocatalysts, revealing potential functions for green hydrogen production under the standard visible light illumination.

Bimetallic Porphyrin-Based Metal-Organic Framework as a Superior Photocatalyst for Enhanced Photocatalytic Hydrogen Production.

The meaningful and rational engineering of porphyrin-based catalysts with multimetallic active sites is very attractive toward photocatalytic hydrogen generation from water decomposition. Herein, three metal organic frameworks (MOFs) based on meso-tetrakis(4-carboxylphenyl)porphyrin (TCPP) were successfully constructed under solvothermal conditions. As a novel architectured photocatalyst (triclinic, C48H29N4O10PdYb), Pd/Yb-PMOF manifested diverse metal active sites, suitable bandgap positions, prominent visible light-collecting capacity, excellent carrier transfer efficiency, and obvious synergistic effect between ytterbium and palladium ions. Consequently, such a bimetallic MOF exhibited strengthened photocatalytic hydrogen evolution performance. Concretely, its hydrogen generation efficiency was up to 3196.42 μmol g-1 h-1 with 2 wt % Pt as a cocatalyst under visible light illumination. Our work demonstrates a promising strategy for highly efficient visible-light catalysts based on bimetallic-trimmed porphyrin MOFs.

Boosting photocatalytic performance of silver phosphate via coupling with P-doped carbon for amoxicillin degradation

Amoxicillin (AMX) could result in risks to ecosystems and organisms in the environment, and photocatalysis is regarded as an effective technology for catalytic degradation of antibiotics. In this study, for the first time, we doped element P into ultra-thin three-dimensional carbon nanosheets to prepare P-doped carbon materials (PCs), and then coupled them with Ag3PO4 to prepare Ag3PO4 @PC composites successfully. The novel composite catalyst was used for photocatalytic degradation of AMX in aqueous solution. Results showed that the photocatalytic performance and cycle stability of Ag3PO4 @PC were much better than that of Ag3PO4 monomer. Under visible light conditions, the degradation efficiency of AMX by the composite catalyst under 3 min of light irradiation could reach 100%, and the corresponding apparent rate constant of AMX degradation was 0.0251 s−1. The DFT calculation results indicated that there was a large built-in potential well at the interface between PC and Ag3PO4, which can effectively reduce the internal recombination of photogenerated electron-hole pairs and improve the photocatalytic performance of the composite catalyst. This study provides an efficient visible light catalyst, and could be referred for appropriate design of innovative visible light photocatalysts.

Performance and mechanisms of photocatalysis of silver phosphate modified by carbon nanosheets doped with both nitrogen and boron for removal of norfloxacin

The photocatalyst technology based on silver phosphate (Ag3PO4) has excellent oxidation ability in the degradation of antibiotic pollutants due to its appropriate energy band structure. However, the high charge recombination efficiency limits the wide application of Ag3PO4. In this study, carbon nanosheets doped with both N and B (NBNS) have excellent charge distribution. The photoactivity of Ag3PO4 was optimized by combining NBNS. After 12 min, Ag3PO4 @NBNS achieved 100% degradation of norfloxacin (NOR), 8.6 times the degradation rate of Ag3PO4 monomer. In addition, NBNS, Ag3PO4 and Ag3PO4 @NBNS were characterized by SEM, TEM, XRD, Raman and XPS. It revealed that there was an intense interface interaction between Ag3PO4 and NBNS, and a built-in electric field (BIEF) was constructed at the interface to achieve rapid separation of photogenerated charges. The DFT calculations results indicated that the doping of B and N could reduce the work function of carbon nanosheets and increase their charge density, which would promote the formation of BIEF between the interface of Ag3PO4 and NBNS. The catalytic reaction mechanism of Ag3PO4 @NBNS was proposed. This work provides a novel photocatalyst for the efficient removal of antibiotics, and sheds light on the use of carbon materials to optimize silver phosphate based photocatalyst, as well as the design of new efficient visible light catalysts.

Self-templated synthesis of core-shell Fe3O4@ZnO@ZIF-8 as an efficient visible-light-driven photocatalyst

Compared to UV-driven catalysts, the utilization of sunlight to design efficient visible light catalysts remains much less explored. Herein, we prepared Fe3O4@ZnO@ZIF-8 three-component core-shell nanoparticles and investigate their corresponding photocatalytic degradation by using Rhodamine B (RhB) as a model contaminant under visible light. It is found that Fe3O4@ZnO@ZIF-8 demonstrates a significant enhancement in the photocatalytic degradation efficiency (98% of RhB was degraded within 100 min) with a reaction rate constant of 0.0292 min−1. These findings mark the significance of precise tailoring of core-shell Fe3O4@ZnO@ZIF-8 for achieving the desired degradation efficiency of organic pollutants under visible light.

Highly Enhanced Photocatalytic Performances of Composites Consisting of Silver Phosphate and N-Doped Carbon Nanomesh for Oxytetracycline Degradation.

Photocatalytic technology based on silver phosphate (Ag3PO4) has excellent potential in removing antibiotic pollutants, but the low separation rate of photogenerated hole-electron pairs restricts the application of the photocatalyst. In this study, it was found that the combination of nitrogen-doped carbon (NDC) with carbon defects and Ag3PO4 can significantly enhance the photocatalytic ability of Ag3PO4. After it was exposed to visible light for 5 min, the photocatalytic degradation efficiency of oxytetracycline (OTC) by the composite photocatalyst Ag3PO4@NDC could reach 100%. In addition, the structure of NDC, Ag3PO4, and Ag3PO4@NDC was systematically characterized by SEM, TEM, XRD, Raman, and EPR. The XPS results revealed intense interface interaction between Ag3PO4 and NDC, and electrons would transfer from Ag3PO4 to the NDC surface. A possible mechanism for enhancing the photocatalytic reaction of the Ag3PO4@NDC composite catalyst was proposed. This study provides a highly efficient visible light catalytic material, which can be a valuable reference for designing and developing a new highly efficient visible light catalyst.

Biotemplated CdS Nano-Aggregate Networks for Highly Effective Visible-Light Photocatalytic Hydrogen Production.

In the last few decades, many new synthesis techniques have been developed in order to obtain an effective visible-light responsive photocatalyst for hydrogen production by water splitting. Among these new approaches, the biotemplated synthesis method has aroused much attention because of its unique advantages in preparing materials with special morphology and structure. In this work, Hydrilla verticillata (L. f.) Royle was used as a biotemplate to synthesize a CdS photocatalyst. The as-synthesized sample had the microstructure of nano-scaled aggregate networks and its activity for photocatalytic hydrogen production was six times higher than that of CdS synthesized without a template in an Na2S-Na2SO3 sacrificial system. The use of Pt and PdS as cocatalysts further improved the hydrogen production rate to 14.86 mmol/g·h under visible-light (λ ≥ 420 nm) irradiation, so the hydrogen production can be directly observed by the naked eye. The results of characterization showed that the as-synthesized CdS photocatalyst has a high specific surface area and narrow band gap, which is favorable for light absorption and photocatalytic reaction. This work provides a new way to search for efficient visible-light catalysts and confirms the uniqueness of a biotemplated synthesis method in obtaining specially structured materials.

Advanced photocatalytic performance of PVP-modified BiOBr materials for the removal of 2,4-DCP and mechanism insight

The BiOBr material is induced by PVP at room temperature to form an efficient visible light catalyst for removing non-dye organic pollutants from wastewater.

A novel magnetically separable BiVO4/N-rGO/CuFe2O4 hybrid photocatalyst for efficient detoxification of p-bromophenol

ABSTRACT The present work deals with simple hydrothermal preparation of magnetically separable BiVO4/N-rGO/CuFe2O4 Z-scheme hybrid photocatalyst for efficient detoxification of p-bromophenol (p-BP). BiVO4 is one of the most efficient visible light catalyst, however, suffers with photo-corrosion and high recombination of charge carriers that restricts its applications. Addition of graphene oxide doped with nitrogen are believed to overcome these issues. Further addition of CuFe2O4 enhances the catalytic degradation and helps in separating the catalyst. With these merits BiVO4/N-rGO/CuFe2O4 could be a promising photocatalyst for detoxification of p-BP. After 60 min of irradiation 94.1 ± 1.2% degradation was achieved by the BiVO4/N-rGO/CuFe2O4 (k = 0.01749 min−1) while only 53.8 ± 2.3% was observed in BiVO4 (k = 0.00674 min−1). The catalyst could be able to recover using external magnet and showed 86.4% of degradation efficiency even after five recycles, which suggested its good stability. The degradation products identification and pathway were proposed based on LC-ESI/MS analysis. Moreover, phytotoxicity assessment of the degradation products was investigated on Phaseolus vulgaris in which the germination index (GI) was about 11.4% for pure p-BP, while it was about 83.03% for degradation products. Thus, the results suggested that more efficient p-BP detoxification was achieved during this photodegradation.

Enhanced visible-light-driven photocatalytic degradation of tetracycline by 16% Er3+-Bi2WO6 photocatalyst

The widespread use of antibiotics in drug therapy and agriculture has seriously polluted the aquatic environment. Bismuth tungstate (Bi2WO6) is a new and efficient visible-light catalyst that is simple to prepare, non-toxic, stable, and corrosion resistant. Nonetheless, its efficiency has remained limited, and erbium (Er) mixing has been tested to address this. Here, a new Er3+-mixed Bi2WO6 photocatalyst was successfully prepared through the one-step hydrothermal method; pigments were characterized via XRD, SEM, BET, XPS, Uv-vis, PL and EIS. The results showed that the 16% Er3+-Bi2WO6 photocatalyst is a 250 nm flower-like nanosheet with a specific surface area of 67.1 m2/g and bandgap (Eg) of 2.35 eV, which provides the basis for superior performance. When the concentration of the catalyst was 0.4 g/L, 94.58% of the tetracycline (TC) solution (initial concentration of 10 mg/L) degraded within 60 min under visible light irradiation (λ ≥ 420 nm). ESR and LC-MS were used to identify the free radicals and intermediates for the degradation of TC pollutants; a photocatalytic degradation system and pathway were proposed. This solar-driven system will ultimately reduce resource consumption, providing a sustainable and energy-saving environmental decontamination strategy.

Hybridizing Engineering Strategy of Decatungstate. 2. Regulated Effect of Doping Transition Metal Ions on Photocatalytic Oxidation Performance of (nBu4N)4W10O32.

This paper discloses a simple and productive hybridizing engineering (HE) strategy for the 3d transition-metal-ion (Mn+ = Fe3+, Fe2+, Co2+, Ni2+)-doped (nBu4N)4W10O32 (Mn+-TBADT) compounds as highly efficient visible-light catalysts. Ultraviolet visible (UV-vis), Fourier transform infrared (FT-IR) and photoluminescence (PL) spectra, and cyclic voltammetry (CV) characterizations indicate that the synthetic quality, redox capacity, and visible light harvesting efficiency of TBADT, especially the separation efficiency of its photogenerated electron-hole pairs, are regulated by the metal ion dopants and gradually improved with a change of the dopant from Fe3+, Fe2+, and Co2+ to Ni2+, along with a continuous and significant enhancement of its photocatalytic efficiency in the visible-light-triggered selective oxidation of ethylbenzene with dioxygens in acetonitrile. The best 0.5 mol % Ni2+-doped TBADT can achieve a ca. 55% conversion under optimal reaction conditions and also exhibits much higher photocatalytic activity for the photo-oxidation of toluene, cyclohexane, and benzyl alcohol compared to pure TBADT. This HE strategy showcases great potential in improving the photocatalysis performance of TBADT.

Vacancy enriched ultrathin TiMgAl-layered double hydroxide/graphene oxides composites as highly efficient visible-light catalysts for CO2 reduction

Ti-containing layered-double-hydroxide (LDH) was exfoliated and coupled with ultrathin graphite (GO) by electrostatic assembly method to fabricate LDH/GO composites for visible-light-driven reduction of CO2. Main focus was to explore the types and quantities of vacancies dependent light response range and product distribution. Interestingly, catalytic behavior of LDH/GO varied with GO ratio increasing as volcano curve, in which 5%GO/LDH exhibited superior efficiency and C1 selectivity. Primarily, delaminated LDH and GO led to structural unsaturated coordination, and thus generated Ti3+-Vo and electron-rich carbon defects. Once coupling with GO, joint function of Ti3+-Vo and transition from C1 s level to conduction band level of reduced valence states expanded absorption range to visible-light. Furthermore, adsorption/activation of CO2 was mainly promoted by electron-rich carbon defects. More importantly, with the aid of Ti3+-Vo and electron-rich carbon defects, two new radicals of HCO3− and CO2− appeared during reaction process over 5GO/LDH, prone to produce C1 rather than H2.

Mesopores octahedron GCNOX/Cu2O@C inhibited photo-corrosion as an efficient visible-light catalyst derived from oxidized g-C3N4/HKUST-1 composite structure

Photo-corrosion of Cu2O photocatalyst considered as an important factor extremely restricts its catalytic activity. However, so far, there are few comprehensive reports on the mechanism of photo-corrosion inhibition and stability improvement of Cu2O in photocatalytic degradation. In this work, oxidized g-C3N4/Cu2O@C (GCNOX/Cu2O@C) visible-light catalysts with protective carbon layer were first prepared using the copper-based metal–organic frameworks (HKUST-1) composite as precursors. The UV–visible DRS, PL, XPS valence-band and Mott-Schottky curves were used to characterize that the formation of carbon layer leads to establishing built-in electric field, shifting of energy bands and photogenerated carrier separation. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) revealed that GCNOX/Cu2O@C had the strongest photo-response current and the lowest interface contact resistance. The photodegradation activity of GCNOX/Cu2O@C was analyzed for Rhodamine B (RhB) and ciprofloxacin (CIP) under low energy visible light irradiation and the degradation kinetic constants were 0.01413 min−1 and 0.03958 min−1, respectively, which were much higher than other as-prepared catalysts. It also exhibited outstanding stability with the 87.4% degradation efficiency in 90 min after four recycles. Furthermore, the characterization of GCNOX/Cu2O@C after the cyclic reactions further proved the ultra-high stability of the carbonized materials. Additionally, on the basis of degradation experiments and photoelectrochemical results, the possible transfer path of photocarriers between material interfaces, photo-corrosion inhibition mechanism of cuprous oxide and the transformation mechanism of active radicals were proposed. This work provided a novel insight for MOFs-derived composites as a highly efficient and stable visible-light catalyst.

Review of strategies for the fabrication of heterojunctional nanocomposites as efficient visible-light catalysts by modulating excited electrons with appropriate thermodynamic energy

Strategies to construct heterojunctional nanocomposites as efficient visible-light catalysts by modulating excited electrons for environmental remediation and clean energy production.

Highly Efficient Visible Light Catalysts Driven by Ti3+‐VO‐2Ti4+‐N3− Defect Clusters

AbstractLocal defect structures play significant roles on material properties, but they are seriously neglected in the design, synthesis, and development of highly efficient TiO2‐based visible light catalysts (VLCs). Here, we take anatase TiO2 nanocrystals that contain (Ti3+, N3−) ions and have the complicated chemical formula of ( )( □z) as an example, and point out that the formation of Ti3+‐VO‐2Ti4+‐N3− local defect clusters is a key missing step for significantly enhancing VLC properties of host TiO2 nanocrystals. Experimental and theoretical investigations also demonstrate the emergent behaviors of these intentionally introduced defect clusters for developing highly efficient VLCs. This research thus not only provides highly efficient visible light catalysts for various practical applications but also addresses the significance of local defect structures on modifying material properties.

Potential visible WO3/GO composite photocatalyst

AbstractGraphene oxide (GO) was synthesized by Hummers method. GO and tungsten oxide (WO3) composites were successfully prepared by deposition of WO3 on GO surface to make efficient visible light catalyst. Scanning electron microscopy of pure GO revealed that GO films are folded with kinked and wrinkled edges. The interspaces layers are partially filled by WO3 nanoparticles with their less wrinkled edges and smooth surface of composite. Moreover, composite sheets are thin and transparent which allow easy penetration of light. EDS showed the presence of C, O, and W in GO/WO3 composites with no impurity. UV‐Vis diffused reflectance spectra showed red shift with the increase in WO3 contents. Raman spectra of GO and GO/WO3 composite show G and D bands. These bands reduced in intensity in composite sample due to removal of oxygenated functional groups with some new peaks of WO3. FT‐IR confirmed successful oxidation of graphite into GO with reduction in GO because oxide‐related bond groups decrease after reduction. The transmittance peaks of WO3 in composite sample are appeared indicating W‐O‐C linkages. The highest visible light activity of the composite is due to easy penetration of light with deposition of WO3, low band gap, and new linkages.

ZnO/WO3 nanostructure as an efficient visible light catalyst

Highly photosensitive ZnO/WO3 photocatalysts were fabricated by wet impregnation of zinc oxide (ZnO) in different contents. Tungsten trioxide (WO3) was synthesized by hydrothermal route. The presence of ZnO inhibited the crystallization of WO3 and caused agglomeration of WO3 nanoparticles surface. The formation of Zn-O-W linkage was studied by X-ray photoelectron emission (XPS) and Fourier transforms Infra-red spectra (FTIR). These linkages were responsible for red shift of absorption peak of composites as compared to individual ZnO and WO3. The band gap was decreased due to incorporation of ZnO in WO3 which promoted the separation of photo-generated carriers. As a result, ZnO/WO3 composite showed extremely high efficiency for MO degradation in comparison with Degussa P25, pure ZnO and WO3. 2.0% ZnO/WO3 composite displayed the highest activity in photocatalytic decomposition of methyl orange (MO) dye.

Erbium doped TiO2 interconnected mesoporous spheres as an efficient visible light catalyst for photocatalytic applications

Semiconductor metal oxides have gained enormous attention due to decomposition of organic pollutant from waste water. Among them TiO2 is one of the most promising photocatalyst with a wide range of applications. It has wide band gap of 3.2 eV which limits its activity to the UV range. Therefore TiO2 (as host matrix) can be doped with a luminescent material to form a phosphorous material which can convert incoming sunlight radiation. One of the interesting luminescent material is Er3+ as it can convert near infrared or visible light to visible and UV light, thus improving the photocatalytic activity of TiO2. In this work, we have synthesized Erbium (Er) doped mesoporous TiO2 spheres by solvothermal method. Effects of Er concentration on the formation and their photocatalytic activity have been investigated. Structural and compositional analysis confirms the presence of Er in the composition. Morphological analysis confirms the formation of mesoporous structure with erbium incorporation on the surface of mesoporous spheres. Elemental mapping confirms the uniform distribution of erbium on the surface of mesoporous structure. Photocatalytic activity of the samples was studied, the samples with 1 mM of Er showed the best photocatalytic activity over the pure TiO2.

The Formation of Defect-Pairs for Highly Efficient Visible-Light Catalysts.

Highly efficient visible-light catalysts are achieved through forming defect-pairs in TiO2 nanocrystals. This study therefore proposes that fine-tuning the chemical scheme consisting of charge-compensated defect-pairs in balanced concentrations is a key missing step for realizing outstanding photocatalytic performance. This research benefits photocatalytic applications and also provides new insight into the significance of defect chemistry for functionalizing materials.