Photocatalytic Catalyst Research Articles

Design and Preparation of a CeVO4/Zn0.5Cd0.5S S-Scheme Heterojunction for Efficient Photocatalytic Hydrogen Evolution

Improving the separation efficiency of photoinduced electron–hole pairs plays a vital role in preparing high-performance photocatalysts. Here, based on the good light corrosion resistance and excellent visible light response of Zn0.5Cd0.5S, as well as the unique catalytic, optical, and electrical properties of CeVO4, we tightly loaded CeVO4 on Zn0.5Cd0.5S by physical coupling to overcome its severe photogenic carrier recombination and obtained a highly efficient photocatalytic catalyst for hydrogen evolution. One the one hand, the close coupling of Zn0.5Cd0.5S and CeVO4 effectively inhibited the serious aggregation of Zn0.5Cd0.5S, which is conducive to the generation of active sites. On the other hand, an S-scheme heterojunction at the contact interface of Zn0.5Cd0.5S and CeVO4 was successfully built. The formation of the S-scheme heterojunction could consume useless electrons and holes and enable the efficient use of photogenerated electrons to participate in the reaction of reducing water. Finally, the hydrogen yield of Zn0.5Cd0.5S/CeVO4 can reach 695.55 μmol in 5 h. Our work provided an idea for the rational design of heterojunction photocatalysts to obtain excellent hydrogen production performance.

Perovskite oxide for emerging photo(electro)catalysis in energy and environment

Using solar energy to catalyse photo-driven processes to address the energy crisis and environmental pollution plays a role in the path to a sustainable society. Many oxide-based materials, especially perovskite oxides, have been widely investigated as catalysts for photocatalysis in energy and environment because of the low-cost and earth-abundant and good performance. At this stage, there is a need to present a scientific-based evaluation of the technologies developed so far and identify the most sustainable technologies and the existing limitations and opportunities for their commercialisation. This work comprehensively investigated the outcomes using various scientometric indices on perovskite oxide-based photo(electro)catalysts for water splitting, nitrogen fixation, carbon dioxide conversion, organic pollutant degradation, current trends and advances in the field. According to the results achieved, efforts in both energy and environment based on perovskite oxides have been initiated in the 1990s and accelerated since the 2010s. China and the United States were identified as the most contributing countries. Based on the results achieved in this study, the main milestones and current trends in the development of this field have been identified. The aim of this research is to provide useful guidelines for the further investigation of perovskite oxide-based catalysts for photoelectrocatalysis and photocatalysis both in energy and environment on the applications such as water splitting, nitrogen fixation, carbon dioxide conversion, and wastewater treatment.

Fabrication of BiVO4/ reduced graphene oxide photocatlyst for hexavalent chromium reduction under visible region

Bismuth vanadate (BiVO4) is widely used as a visible light photocatalyst for elimination of organic and inorganic pollutants in aqueous solution. An integration with few layer graphene oxide into BiVO4, significantly enhance the photocatalytic activity in the visible region due to it’s high charge transport and separation. Herein, we have designed BiVO4 on reduced graphene oxide (rGO) photocatalyst synthesised via simple solution phase method. BiVO4 nanocrystals nanoplates were fabricated using bismuth (III) nitrate, ammonium metavanadate with ammonium hydroxide, and polyethylene glycol as a stabilising agent. The resulting photocatalytic catalyst showed an excellent activity towards Cr(VI) removal (as a model inorganic pollutant) under visible light, which is evidenced with photoelectrochemical studies. The photocatalytic performance for Cr(VI) removal rates over BiVO4/rGO showed much higher activity than BiVO4 in visible light. Furthermore, the catalyst efficiency was confirmed through photoelectrochemical, and optoelectronic properties.

Cobalt Nanoparticles Encapsulated in Hollow Carbon Nitride Nanotubes for Efficient Photocatalytic Hydrogen Evolution

A high‐efficiency and low‐cost photocatalytic catalyst containing cobalt nanoparticles wrapped in hollow carbon nitride nanotubes is designed and the high‐efficiency Schottky junction is constructed. Profiting from the framework support of the hollow carbon nitride nanotubes, the cobalt nanoparticles are evenly distributed. The introduction of cobalt nanoparticles not only provides a large number of active sites for hydrogen evolution, but also accelerates the migration rate of photogenerated carriers by forming a heterojunction with the carbon nitride. The narrowing of the bandgap after catalyst recombination facilitates the excitation of electrons, thereby accelerating the rate of hydrogen evolution of the catalyst. In addition, the composite catalyst has a larger specific surface area, better light absorption capacity, and higher photoresponse intensity. The hydrogen evolution rate of the composite catalyst in 5 h reaches 16 687.3 μmol g−1, equal to 84 times that of original carbon nitride. Herein, a new strategy for designing non‐noble metal nanoparticles wrapped in hollow carbon nitride nanotubes to expose more active sites to achieve an efficient hydrogen evolution reaction is provided.

Exploring hierarchical porous silica-supported Ag3PO4 as high-efficient and environmental-friendly photocatalytic disinfectant

Silver orthophosphate (Ag3PO4) is an attractive photocatalytic catalyst for disinfection and degradation, but its instability arising from silver release generates significant environmental issue. Aiming to develop a highly efficient and environmental-friendly catalyst, we synthesized Ag3PO4 nanoparticle incorporated hierarchical porous silica (Ag3PO4@h-SiO2) as a novel high-performance photocatalytic catalyst without observed silver release. Brain-like hierarchical porous SiO2 (h-SiO2) brings a scaffold support with high surface areas, and the h-SiO2 surface modified thiols are able to anchor in situ formed 10 nm Ag3PO4 to eliminate silver release. Systematic investigations revealed that because of its structural advantages, Ag3PO4@h-SiO2 show excellent disinfection and degradation ability under visible-light irradiation and stable characteristics without obviously observed silver leaching during photo-oxidation operation. In-depth scavenger study reveals Ag3PO4@h-SiO2 as an effective semiconducting photocatalyst stimulates the production of photo-generated reactive species, which dominate its distinguished disinfection performance via photo-oxidation.Graphical abstractAg3PO4 are anchored to thiol modified hierarchical porous SiO2 to produce a visible-light responsive photocatalyst of Ag3PO4@h-SiO2. The enhanced catalytic sites and surface areas promote pathogen disinfection, and the structure advantages minimize silver release to environment. Both H2O2 and holes being generated in photocatalysis dominate overall disinfection activity.

Bimetallic silver/bismuth-MOFs derived strategy for Ag/AgCl/BiOCl composite with extraordinary visible light-driven photocatalytic activity towards tetracycline

The rod-like Ag/AgCl/BiOCl materials were successfully fabricated by calcination of the self-sacrificial template of silver/bismuth bimetallic-organic frameworks (BMOFs) under air atmosphere in order to achieve more desirable photocatalytic activity towards tetracycline (TC). The microstructures, content, morphologies, photogenerated electron-hole pair, and photocatalytic activities were characterized for all obtained catalysts. Ag/AgCl/BiOCl obtained through the silver/bismuth BMOFs derived strategy enhanced light absorption ability in visible light region with modified energy band structures, further decreasing the recombination efficiency of photo-induced carriers with enhanced performance during photocatalysis process. TC degradation evaluations driven by visible light revealed that Ag/AgCl/BiOCl possessed superior photocatalytic activity compared to BiOCl, as well as some reported in the literature. Additionally, Ag/AgCl/BiOCl demonstrated remarkable stability during TC photocatalytic reactions, maintaining above 84% initial photocatalytic activity after second cycle. In general, Ag/AgCl/BiOCl material benefited TC degradation from aqueous solutions. Our work opens up new perspectives for advanced uniform-sized photocatalytic catalyst using bimetallic MOFs as self-sacrificial templates.

A (4,12)-connected coordination polymer: photocatalytic degradation of dyes and effects on cerebral edema care by regulating superoxide dismutase activity

With the improvement of people's living standards and the development of modern industry, water pollution is becoming more and more serious in the global environmental pollution. Coordination polymers have the potential to address the above mentioned problem, but their poor water stability and weak light adsorption ability in the visible light region largely restrict their applications. In this study, a new coordination polymer (CP) formulated as {(NH4)2·[Cu11(μ4-OH)6(CN)6(trz)12]}n (1) was produced with the reaction between μ3-N1,N2,N4-triazolate (trz) and Cu(NO3)2·3H2O under the solvothermal reaction conditions. Complex 1 could be utilized as a photocatalytic catalyst for the degradation of the organic dyes of MB (Methylene Blue) and RhB (Rhodamine B) which shows better performance than that of TiO2 (20 nm). For the treatment of the cerebral edema care after ischemia reperfusion injury, the brain water content was evaluated firstly after treated with compound, and the superoxide dismutase expression in the brain cells was also measured through real time reverse transcription polymerase chain reaction (RT-PCR).

TiO2 doped HKUST-1/CM film in the three-phase photocatalytic ammonia synthesis system

Photocatalytic synthesis of ammonia from N2 and H2O at room temperature and atmospheric pressure is considered to be a safe, clean and sustainable method. Due to the low solubility and diffusion coefficient of nitrogen in water, the rate of ammonia synthesis is significantly hindered. As a result, we develop a kind of thin film photocatalyst, which can be used in gas-liquid-solid three phase reaction system to solve this problem. The catalyst bases on HKUST-1 thin film with high nitrogen adsorption performance and supported with TiO2 nanoparticles with photocatalytic nitrogen fixation performance. The constructed binary composite photocatalyst has a stable structure under a 300 W xenon lamp, which exhibits good photoelectric conversion performance. While characterizing the structure and photoelectric performance of the material, the performance of photocatalytic ammonia synthesis was investigated. The highest ammonia synthesis efficiency was 0.048 μmol·h−1·cm−2, and its performance was 2.8 times that of TiO2/CM catalyst under the same conditions. The thin film catalyst does't contain any N substance and won't interfere with the ammonia synthesis reaction. The preparation process is simplified by directly using the copper source in the CM without additional metal reagent. Moreover, it provides a new idea for the design of photocatalytic catalysts for ammonia synthesis.

CdS nanoparticles modified Ni@NiO spheres as photocatalyst for oxygen production in water oxidation system and hydrogen production in water reduction system

The exploration of bifunctional catalysts to produce both hydrogen and oxygen will accelerate the progress of overall water-splitting. This paper introduces a facile method to fabricate bifunctional photocatalysts toward the water splitting by doping nano CdS with S vacancies on Ni@NiO nano-spheres. A serious of photocatalytic catalysts were developed and subsequently characterized, the two half-reactions of photocatalytic water splitting were studied in detail by using sacrificial agents, the hydrogen output at 41699 μmol g−1 h−1 (AQE 28.5%, λ = 420 nm) while the evolution of O2 is as high as 55120 μmol g−1 h−1 (AQE 35.7%, λ = 450 nm). It is a strategy that the presence of Ni@NiO can trigger the S vacancy in CdS to act as an effective electron trap, the p-n junction of NiO-CdS, as well as the Schottky barrier between NiO and Ni, can change the dynamic characteristics of photogenerated electrons and prolong their life. These prolonged photogenerated electrons can initiate stable and effective photocatalytic redox reactions.

Modification of photocatalyst Ti-Pillared clay by Zn metal addition for decolorization process of organic liquid waste

Black liquor produced from a pretreatment process of bioethanol using the lignocellulose material, such as an empty palm bunch. Black liquor is organic liquid waste and should be treated before release to the environment. One of the degradation processes of black liquor is by the photocatalytic reaction using the Ti-Pillared Clay (Ti-PiLC) catalyst. However, there is a limitation of process condition if using a Ti-PiLC catalyst; the degradation process should be conducted under a UV light source. This study is focused on the modification of photocatalytic catalyst Ti-PiLC by adding Zn metal (Ti-Zn/PiLC), thus the degradation process of black liquor could be conducted on a visible light source. Characterizations of the prepared photocatalysts were obtained using XRD, BET, TPD, TGA, SEM, TEM and UV-Vis spectrophotometer for the degradation degree. Although the degradation process of black liquor could be conducted on the visible light source, the degradation degree was still minor compared with only using Ti-PiLC photocatalyst. It is assumed that combination Ti and Zn as the active metals of the photocatalyst was not good enough to enhance the degradation process of black liquor even on the visible light source, perhaps using other metal, such as cerium (Ce).

La2O3-modified graphite carbon nitride achieving the enhanced photocatalytic degradation of different organic pollutants under visible light irradiation

Lanthanum (La) has some advantages of smaller radius, cheaper price and higher affinity for oxygen in rare-earth-metallic element group, and La2O3 modification may be helpful to further extend the life of photon-induced electrons and holes due to its rich energy levels, special optical properties and 4f electronic transition properties. Inspired by these items, graphite carbon nitride (GCN)/La2O3 (denoted as CN/La) was prepared by a facile hydrothermal method. The characterizations of photocatalysts were conducted using X-ray diffraction, field emission scanning electron microscope, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and N2 adsorption-desorption isotherms. The Methyl orange (MO), Methylene blue (MB) and Rhodamine B (RhB) were applied to characterize the photocatalytic performances of CN/La-x% photocatalysts under visible light irradiation (λ > 420 nm). CN/La-6% exhibited the optimal photodegradation efficiency, and 66.6% of MO, 99.5% of RhB and 100% of MB could be removed in 120 min. The BET surface area was improved from 8.357 m2g-1 to 67.818 m2g-1 and the light absorption edge shifted from 468 nm to 484 nm. In addition, the photocurrent density increased from 0.96 μA/cm2 to 4.82 μA/cm2. The improved photodegradation efficiency was attributed to larger BET surface area, extended optical absorption and enhanced charge carrier separation. More interestingly, this work lays the foundation for practical application of the La2O3-modified GCN material as the photocatalytic catalysts.

A Highly Efficient Composite Catalyst Constructed From NH2-MIL-125(Ti) and Reduced Graphene Oxide for CO2 Photoreduction.

Substantial consumption of fossil fuels causes an increase in CO2 emissions and intensifies global pollution problems, such as the greenhouse effect. Recently, a new type of ultra-low-density porous material, metal-organic frameworks (MOFs), has been developed for the photocatalytic conversion of CO2. Herein, a composite photocatalytic catalyst based on NH2-MIL-125(Ti) and reduced graphene oxide (rGO@NH2-MIL-125) was fabricated through a facile “one-pot” process. The acquired materials were characterized to obtain their structures, morphologies, and optical information. The experimental results showed that methyl formate (MF) was the predominant reaction product, and rGO@NH2-MIL-125 exhibited the highest yield of 1,116 μmol·g−1·h−1, more than twice that of pure MIL-125. The high photoactivity of rGO@NH2-MIL-125 can be ascribed to the effective spatial separation and transfer of photoinduced carriers, largely due to the synergistic effect of amino functionality and rGO incorporation. rGO@NH2-MIL-125 also displayed acceptable repeatability in cyclic runs for CO2 reduction.

Photocatalytic enhancement mechanism of direct Z-scheme heterojunction O-g-C3N4@Fe-TiO2 under visible-light irradiation

A novel visible-light response heterojunction photocatalytic catalyst was developed in this study. The fragmented O-g-C3N4 discontinuously coated on the surface of Fe-TiO2, which exhibited excellent photocatalytic activity, photocatalytic stability and long-term durability under visible light irradiation. Compared with pristine O-g-C3N4 and Fe-TiO2, the photocatalytic degradation efficiency of O-g-C3N4@Fe-TiO2 was 1.32 and 1.65 times higher than that of the former two, respectively. Compared with the electrically neutral Fe-TiO2, the electronegative O-g-C3N4 demonstrated excellent adsorption capacity for the cation MB+. The proper band structure of the element-doped O-g-C3N4 and Fe-TiO2 catalysts ensured the absorption capacity of visible light by O-g-C3N4@Fe-TiO2. The Z-scheme transfer mechanism of photo-generated carriers in O-g-C3N4@Fe-TiO2 was constructed, which could not only promote the separation of holes in the valence band of Fe-TiO2 and the electrons in the conduction band of O-g-C3N4 effectively, but also could retain the holes and electrons with stronger redox abilities in the O-g-C3N4@Fe-TiO2 catalyst.

Experimental and DFT insights of BiVO4 as an effective photocatalytic catalyst for N2O decomposition

A series of BiVO4 semiconductor photocatalysts with different crystallographic forms and crystallite sizes are designed and controllably constructed by a facile hydrothermal method, and their photocatalytic activities are examined for N2O decomposition. It is found that monoclinic BiVO4 prepared at 150 °C shows the highest activity because of its strongest adsorption ability for visible light and highest separation efficiency for photogenerated charge carriers, which achieves 26.7% N2O conversion at 25 °C after 12 h of irradiation. Oxygen vacancy significantly influences the photocatalytic performance of N2O decomposition, which can not only promote the formation of excess electrons but also reduce the activation energy barrier. Moreover, DFT + U calculation is employed to explore the electronic properties of the catalyst at the microscopic level, as well as the reaction pathway of N2O decomposition over these photocatalysts, is illustrated.

Constructing a novel Bi2SiO5/BiPO4 heterostructure with extended light response range and enhanced photocatalytic performance

To further extend the light response range of BiPO4 and meanwhile keep its strong photocatalytic oxidation ability, the design of a type-II heterojunction by coupling BiPO4 with a narrower band gap semiconductor of Bi2SiO5 as a novel and efficient photocatalytic catalyst has been successfully realized through a simple co-precipitate method. Moreover, under 365 nm UV light irradiation, pure BiPO4 shows no photo-activity, whereas the optimal Bi2SiO5/BiPO4 heterostructure exhibits highly enhanced photocatalytic activity than pure Bi2SiO5 in systems of photo-degradation over phenol and MB, which is 4.36 times and 1.13 times the values of pure Bi2SiO5. Experimental results reveal that the superior photocatalytic performance can be attributed to the synergetic effect of the evidently improved charge separation ability via the heterojunction, good crystallinity, expanded light absorbance and the moderate BET specific surface area.

Highly Efficient and Stable CO2 Reduction Photocatalyst with a Hierarchical Structure of Mesoporous TiO2 on 3D Graphene with Few-Layered MoS2

The development of photocatalysts of CO2 reduction based on stable and Earth-abundant materials is essential for utilizing solar energy and storing it in chemical forms. Here, we report the synthesis and characterization of a composite material consisting of a few layers of MoS2 on a hierarchical porous structure of mesoporous TiO2 and macroporous 3D graphene aerogel (TGM) as a high-performance, robust, noble-metal-free photocatalyst of CO2 reduction. The hierarchical structure contributed to the high photocatalytic catalyst performance, which was investigated by controlling the morphologies of the mesopores and macropores. By optimizing the relative amounts of each component and the configuration of the composite, a TGM system was fabricated. The resulting TGM showed a lower extent of charge recombination and a higher photocurrent density, and hence a higher CO photoconversion rate (92.33 μmol CO/g·h) than those of other composite combinations, i.e., bare TiO2, TiO2-graphene, TiO2-MoS2, and TiO2-graphene...

Graphene Photocatalytic Catalyst Preparation and Properties of Composite Materials Research

Using a pan of the Ag/TiO2/rGO ternary composites, including ethanol as solvent, not only as a reductant in GO with the reduction of silver nitrate, the addition of ammonia water can not only catalytic hydrolysis TBOT to TiO2 can also form with silver nitrate silver ammonia solution is conducive to the reduction of silver nitrate. And the GO surface exist a large amount of oxygen-containing groups can provide nucleation points for the growth of the nanoparticles. Can control the dosing raio of TBOT and GO different morphology of TiO2/rGO composite material is prepared. Photocatalytic degradation of methylene blue test studied Ag modified enhanced the photocatalytic activity of TiO2 light influence.

Syntheses, structures, properties of a series of coordination polymers with flexible bis(imidazole) and dicarboxylate ligands

Seven coordination polymers, [Co(bix)(ndc)]n (1), [Co2(bix)(glu)2]n (2), {[Zn(bix)(male)]·H2O}n (3), [Zn2(bix)(pim)2]n (4), [Zn(bix)(aze)]n (5), {[Zn(bix)(mbda)]·H2O}n (6) and [Zn(bix)(adc)]n (7), were synthesized (bix=1,4-bis(2-methyl-imidazol-1-methyl)benzene, ndc=1,4-naphthalenedicarboxylate, glu=glutarate, male=maleicate, pim=pimelate, aze=azelaicate, mbda=1,3-benzenediacetate, adc=1,3-adamantanedicarboxylate). 1 shows an unusual 4-connected self-catenated 3D network. 2 is a 6-connected self-catenated 3D network based on the [Co2(COO)4] unit. 3 shows a special 2D (6,3) network, with six Zn(II) atoms at six corners and four bix and two double male ligands at six edges. 4 is a (3,4)-connected 3D network. 5 and 6 show the 2D (4,4) network. 7 consists of one-dimensional chains containing two alternative kinds of rings, [Zn2(adc)2] and [Zn2(bix)2]. The diverse structures indicate that the structures of the coordination polymers can be tuned by the right combination of appropriate flexible bis(imidazole) ligand, bix, the metal ions and dicarboxylate ligands. 1 and 2 are effective photocatalytic catalysts for the degradation of methyl orange. The luminescence of 3–7 and thermal stability of 1–7 were also investigated.

Enhanced Visible-Light-Driven Photocatalytic H2 Evolution from Water on Noble-Metal-Free CdS-Nanoparticle-Dispersed Mo2C@C Nanospheres

Developing efficient noble-metal-free catalysts for photocatalysis under the irradiation of visible light, which is the main part of sunlight (44%), would represent a significant step toward making photocatalysis a more competitive strategy for solar energy utilization. Herein, nanospheres (∼200 nm) containing dimolybdenum carbide and carbon (Mo2C@C) were used to support CdS nanoparticles (∼5 nm) to form a noble-metal-free CdS/Mo2C@C photocatalyst. CdS/Mo2C@C shows an enhanced visible-light-driven photocatalytic H2 evolution from water, with a H2 evolution rate of 554.3 μmol h–1, which is about 2 times higher than that on the widely used noble-metal-based CdS/Pt photocatalyst. Improved absorption of the visible light and separation of the photogenerated electron–hole pairs could be the origins for the enhanced photocatalytic activity of CdS/Mo2C@C. The findings of this work will open a new door for fabricating efficient noble-metal-free photocatalysts for visible-light-driven photocatalysis.

Solar-assisted photodegradation of isoproturon over easily recoverable titania catalysts

An easily recoverable homemade TiO2 catalyst (GICA-1) has been evaluated during the overall photodegradation process, understood as photocatalytic efficiency and catalyst recovery step, in the solar light-assisted photodegradation of isoproturon and its reuse in two consecutive cycles. The global feasibility has been compared to the commercial TiO2 P25. The homemade GICA-1 catalyst presented better sedimentation efficiency than TiO2 P25 at all studied pHs, which could be explained by its higher average hydrodynamic particle size (3μm) and other physicochemical surface properties. The evaluation of the overall process (isoproturon photo-oxidation + catalyst recovery) revealed GICA-1 homemade titania catalyst strengths: total removal of isoproturon in less than 60min, easy recovery by sedimentation, and reusability in two consecutive cycles, without any loss of photocatalytic efficiency. Therefore, considering the whole photocatalytic cycle (good performance in photodegradation plus catalyst recovery step), the homemade GICA-1 photocatalyst resulted in more affordability than commercial TiO2 P25. Graphical abstract.