Bimetallic Photocatalysts Research Articles

Critical trigger of self-assembled bimetallic Fe/Mn-MOF with SnS2 heterojunctions by persulfate activation for efficient tetracyclines photodegradation

Developing advanced strategies, including exposing active site centers, regulating coordination environments, controlling crystallographic facets, optimizing electronic structures and constructing defects for enhancing photocatalytic performance is of great significance to improving the ecosystem. In this study, a novel self-assembled bimetallic Fe/Mn-MOF with SnS2 Z-scheme heterojunction photocatalyst was designed using a facile multistep solvothermal method. Benefiting from the interfacial heterojunction synergistic effect, the photocatalysts exhibited an outstanding catalytic performance. Nearly 91.4% efficiency of tetracyclines was degraded within 80 min through the assistance of a persulfate-based advanced oxidation process. DFT calculations utilizing the Fukui index identified the sites vulnerable to attack by the active species. As demonstrated by the trapping experiments and electron spin resonance (ESR), the involved oxygen-active species (•O2− and 1O2) facilitated the rapid degradation of tetracycline. The degradation pathways were further guided in the elucidation of the rationale mechanism and the toxicity of derived intermediates was revealed. This work opens a new strategy for the rational design of bimetallic photocatalysts, emphasizing interface-modulated heterojunctions for efficient solar energy conversion.

CuCl2/FeCl3 Bimetallic Photocatalyst for Sustainable Ethylene Production from Ethanol via Recoverable Redox Cycles.

Photocatalytic conversions of ethanol to valuable chemicals are significant organic synthesis reactions. Herein, we developed a CuCl2/FeCl3 bimetallic photocatalyst for sustainable dehydration of ethanol to ethylene by recoverable redox cycles. The selectivity of ethylene was 98.3% for CuCl2/FeCl3, which is much higher than that of CuCl2 (34.5%) and FeCl3 (86.5%). Due to the ligand-to-metal charge transfer (LMCT) process involved in generating the liquid products, the CuCl2/FeCl3 catalyst will be reduced to CuCl/FeCl2. Oxygen (O2) is required for the recovery of CuCl2/FeCl3 to avoid exhaustion. The soluble Fe3+/Fe2+ redox species deliver catalyst regeneration properties more efficiently than single metal couples, making a series of redox reactions (Cu2+/Cu+, Fe3+/Fe2+, and O2/ethanol couples) recyclable with synergistic effects. A flow reactor was designed to facilitate the continuous production of ethylene. The understanding of bimetallic synergism and consecutive reactions promotes the industrial application process of photocatalytic organic reactions.

Bimetallic Pt-IrOx/g-C3N4 Photocatalysts for the Highly Efficient Overall Water Splitting under Visible Light

Two series of bimetallic photocatalysts (0.5% Pt/0.01–0.5% IrOx/g-C3N4 and 0.1% Pt/0.01–0.1% IrOx/g-C3N4) were synthesized by the thermolysis of melamine cyanurate and a successive deposition of platinum and iridium labile complexes (Me4N)2[Pt2(μ-OH)2(NO3)8] and fac-[Ir(H2O)3(NO2)3. The synthesized photocatalysts were studied by a set of physicochemical analysis techniques. Platinum exists in two states, with up to 60% in metallic form and the rest in the Pt2+ state, while iridium is primarily oxidized to the Ir3+ state, which was determined by X-ray photoelectron spectroscopy (XPS). The specific surface area (SBET), which is determined by low-temperature nitrogen adsorption, ranges from 80 to 100 m2 g−1 and the band gap energy (Eg) value is in the range of 2.75–2.80 eV as found by diffuse reflectance spectroscopy (DRS). The activity of the photocatalysts was tested in the photocatalytic production of hydrogen from ultrapure water under visible light (λ = 400 nm). It was found that the splitting of water occurs with the formation of the stochiometric amount of H2O2 as an oxidation product. Two photocatalysts 0.5% Pt/0.01% IrOx/g-C3N4 and 0.1% Pt/0.01% IrOx/g-C3N4 showed the highest activity at 100 μmol h−1 gcat−1, which is among the highest in H2 production published for such systems.

Facile preparation and photocatalytic performance of bimetallic photocatalyst FcC2Cu

Facile preparation and photocatalytic performance of bimetallic photocatalyst FcC2Cu

Preparation strategy of bimetallic MOF hollow photocatalysts for hydrogen evolution

Hollow structure materials have been proved to be excellent photocatalysts due to their advantages in the separation of electron-hole pairs. However, the synthesis of such materials is complex, time-consuming, and poor versatility. In this study, Cu-DHTP/ZIF-67 (DHTP = 2,5-dihydroxyterephthalic acid) hollow materials containing both Co and Cu were designed and synthesized by a simple one-step etching and ligand exchange strategy. It is worth noting that the bimetallic hollow catalyst can be synthesized in the presence of both Cu(Ⅱ) and DHTP within 5 min at room temperature. The synthesized hollow bimetallic catalyst has improved photoresponse performance and electron-hole pair separation ability, which results in the best catalytic performance compared with DHTP/ZIF-67, Cu/ZIF-67, and ZIF-67 when used in the photocatalytic water splitting reaction. The hydrogen evolution yield of Cu-DHTP/ZIF-67 can reach 39.7 mmol g−1, which is 6 times than that of pure ZIF-67. This study demonstrates the promising potential of Cu-DHTP/ZIF-67 photocatalyst in the field of photocatalytic water reduction and hydrogen evolution, and provides a new idea for designing and preparing more hollow structure bimetallic photocatalysts with excellent performance.

Bio-inspired citric acid-based bimetallic photocatalyst for nitrogen fixation from air under ambient conditions

Discovery of effective materials for photocatalytic nitrogen fixation under ambient conditions provides new opportunities for sustainable futures. Nitrogenase provides the best example of environmentally friendly nitrogen reduction. Inspired by homocitrate's specific activating effect on nitrogenase, citric acid was used instead of homocitric acid to prepare citric acid-based bimetallic organic frameworks (MOFs). Metals such as cerium and copper as bimetallic centers were coordinated with citric acid to mimic FeMo bimetallic active center in the M cluster. The results show that the morphology, structure and photocatalytic activity of the catalysts has been significantly affected by the amount of citric acid. The molar ratio of total metal to citric acid of 1.5:20 had the best ammonia evolution rate from air at a normal temperature and pressure (NTP), which was as high as 1027.6 μg g−1 h−1. It was further confirmed by the numerically study of the interactions between light and the synthesized photocatalytic particles, which can be intuitively seen that CeCu@CA-20 can support more surface charges. This work provides an effective strategy for citrate-based MOF photocatalysts and offers a new idea for nitrogenase biomimetics.

Metal organic framework-derived Zr/Cu bimetallic photocatalyst for the degradation of tetracycline and organic dyes

The exploitation of tetracycline antibiotics (TCs) has caused significant hazards to both the humans as well as the environment. As a result, developing efficient strategies to eliminate these contaminants is both important and practicable. Photocatalytic degradation appears to be one of the most potential techniques for extracting antibiotics. Semiconductors seem to be the most extensively used photocatalysts even though their performance is still hampered by light absorption limitations and poor charge separation. MOFs are worthy choices for the construction of hierarchical nanostructures with semiconductors to address the foregoing concerns because of their extraordinary features including better surface area and extensive active sites. Zr/Cu-MOF was synthesised by precipitation refluxing method and its efficacy as a photocatalyst for the degradation of TC antibiotics and poisonous dyes such as rhodamine B and methylene blue was examined in this study. The Zr/Cu-MOF displayed excellent efficacy for degradation of tetracycline (93 % in 80 min), Rhodamine B (96 % in 70 min) and methylene blue (96 % in 50 min) with rate constant of 0.0308, 0.052 and 0.068 min−1. The contribution of reactive species in antibiotics and dye degradation was confirmed by radical scavenging investigations which showed that.OH radical has a significant role in photocatalytic decomposition. In addition, tests using liquid chromatography-mass spectrometry (LC-MS) were carried out in order to predict a probable mechanism for TC degradation.

Controllable preparation of hierarchical MnCo bimetallic photocatalyst and the effect of atomic ratio on its photocatalytic activity

In recent years, bimetal has become an important branch of catalysis because of its unique interatomic synergistic activity. In this study, the effects of different preparation temperatures and atomic ratios on the activities of manganese-cobalt bimetallic photocatalysts and their catalytic mechanisms were investigated. Specifically, a series of hierarchical MnCo bimetals were prepared at 180 ∼ 200 ℃ with Mn:Co ratios of 2:1, 1:1 and 1:2 by a simple “hydrothermal/reduction” method. The results of the photoelectrochemical tests and density functional theory (DFT) show that the light absorption range, photocurrent, photovoltage and energy density of the materials are greatly affected by the preparation temperature and atomic ratio. The degradation rate of the representative MnCo2-190 bimetal to norfloxacin (NOR) reached 98.91% within 65 min. In addition to the characteristics of CoMn2 and MnCo, MnCo2 excites local surface plasmon resonance (LSPR) under light irradiation, resulting in strongest catalytic activity through Landau damping effect.

Low Metal Loading (Au, Ag, Pt, Pd) Photo-Catalysts Supported on TiO2 for Renewable Processes.

Photo-catalysts based on titanium dioxide, and modified with highly dispersed metallic nanoparticles of Au, Ag, Pd and Pt, either mono- or bi-metallic, have been analyzed by multiple characterization techniques, including XRD, XPS, SEM, EDX, UV-Vis and N2 adsorption/desorption. Mono-metallic photo-catalysts were prepared by wet impregnation, while bi-metallic photocatalysts were obtained via deposition-precipitation (DP). The relationship between the physico-chemical properties and the catalyst’s behavior for various photo-synthetic processes, such as carbon dioxide photo-reduction to liquid products and glucose photo-reforming to hydrogen have been investigated. Among the tested materials, the catalysts containing platinum alone (i.e., 0.1 mol% Pt/TiO2) or bi-metallic gold-containing materials (e.g., 1 wt% (AuxAgy)/TiO2 and 1 wt% (AuxPtz)/TiO2) showed the highest activity, presenting the best results in terms of productivity and conversion for both applications. The textural, structural and morphological properties of the different samples being very similar, the main parameters to improve performance were function of the metal as electron sink, together with optoelectronic properties. The high activity in both applications was related to the low band gap, that allows harvesting more energy from a polychromatic light source with respect to the bare TiO2. Overall, high selectivity and productivity were achieved with respect to most literature data.

Bio-Inspired Citric Acid-Based Bimetallic Photocatalyst for Nitrogen Fixation from Air Under Ambient Conditions

Bio-Inspired Citric Acid-Based Bimetallic Photocatalyst for Nitrogen Fixation from Air Under Ambient Conditions

Controllable Preparation of Hierarchical Mnco Bimetallic Photocatalyst and the Effect of Atomic Ratio on its Photocatalytic Activity

Controllable Preparation of Hierarchical Mnco Bimetallic Photocatalyst and the Effect of Atomic Ratio on its Photocatalytic Activity

Ni-MOL/In2Se3 heterostructure construction with mixed metal (Ti/Ni) for efficient photocatalytic tetracycline degradation

To investigate the mechanism of bimetallic 2-dimension (2D) catalyst existing in the current photocatalytic degradation process, the tetracycline (TC) degradation performance and mechanism by bimetallic 2D photocatalyst was studied extensively. Nickel metal-organic layer (Ni-MOL) and In2Se3, a typical 2D semiconductor photocatalyst, shows great potential for photocatalytic degradation of TC. Herein, an In2Se3 assisted Ni-MOL composite bimetallic photocatalyst was assembled, of which could obtain the degradation rate of 96.4% within 90 min for TC under visible light. Ni-MOL was the main active site for TC degradation by photo-induced holes which located at the Ni atom active site during the photocatalytic process. The role of In2Se3 and the element of Ti in Ni-MOL was to assist Ni-MOL by providing more photo-induced carriers and inhibiting carrier recombination. This work makes a contribution to the application of 2D bimetallic photocatalytic in TC degradation.

Rational design of bimetallic photocatalysts based on plasmonically-derived hot carriers.

Hot carriers generated by plasmonic excitations have recently opened up new avenues in photocatalysis. The transfer of these energetic carriers to adjacent molecules can promote chemical transformations that are important for hydrogen generation by water splitting, CO2 reduction and degradation of organic pollutants. Here, we have developed and optimised a plasmonic hot-carrier catalytic system based on silica nanoparticles decorated with plasmonic gold nanoparticles as a source of hot carriers, equipped with platinum nanoclusters as co-catalyst for the enhancement of hot-carrier extraction. The latter plays a triple role by providing: a surface favourable for molecular adsorption; hot-electron generation near the nanoclusters due to field enhancement effects and electron momentum relaxation facilitating the electron transfer across the metal surface, exactly where molecules are adsorbed. The combination of plasmonic and catalytic metals in nano-heterostructured devices provides a new platform for photocatalytic processes and is of significant interest for future solar-based clean technologies.

A ruthenium and palladium bimetallic system superior to a rhodium co-catalyst for TiO2-photocatalyzed ring hydrogenation of aniline to cyclohexylamine

Cyclohexylamine (CHA) is used as an important raw material in chemical industries. Since the production of CHA requires a high temperature and excess amounts of hydrogen gas (H2) and ammonia, the development of a simple reaction operated under milder conditions using a safe compound is indispensable for achieving sustainable chemistry. A highly selective ring hydrogenation of aniline (AN) to CHA over a titanium(IV) oxide photocatalyst having a co-catalyst in water at room temperature, in which oxalic acid was used as the hydrogen source in place of H2, is described in this paper. Among TiO2 photocatalysts having co-catalysts, Rh-TiO2 showed high activity for CHA production, while Pd-TiO2 and Ru-TiO2 showed negligible activity. When a bimetallic photocatalyst, Ru/Pd-TiO2, was used, the yield was larger than that when Rh-TiO2 was used. Metal particles loaded on TiO2 were observed by using TEM, and electronic states of Ru and Pd were evaluated by using XPS. Interactions among metal, AN and CHA were investigated through adsorption experiments. Based on the results, active sites for AN hydrogenation are discussed.

Photocatalytic degradation and kinetic modeling of azo dye using bimetallic photocatalysts: effect of synthesis and operational parameters.

Industrial wastewaters are the major source polluting the surface and ground water resources. Pollutants released along with the untreated textile industry wastewaters are responsible for the great damage to the natural resources like water. Considering the hazardous effects of the azo dyes (textile coloring agents) and their byproducts, there is a need to develop cost-effective and efficient treatment method for the textile wastewaters as such dyes have been reported as toxic, mutagenic, and carcinogenic and can cause direct demolition of aquatic communities. One of the possible and effective treatment methods is the use of TiO2 photocatalysis due to its chemical stability, low cost, and non-toxic nature. The present study explored the photocatalytic potential of anatase-type of bimetallic Cu-Ni/TiO2 photocatalysts under visible light irradiation for possible photocatalytic degradation and mineralization of Methyl Orange (MO), as model azo dye. The focus was to correlate the synthesis (different calcination temperatures, phase composition of TiO2 either anatase or rutile, and metal ion loading in terms of concentration and composition (Cu:Ni)) and operational parameters (photocatalyst loading, pollutant concentration, and irradiation time) that were believed responsible for the enhanced photocatalytic performance. Blank experiments were carried out to check the effect of metal loading in comparison to bare TiO2 and effect of absence or presence of light and photocatalysts on MO photodegradation. Results obtained using bimetallic photocatalysts are promising as compared to bare TiO2 as 100% MO removal and ~ 90% %COD removal were obtained in 90min of irradiation, obeying a pseudo-first-order kinetics with photocatalytic reaction via the Langmuir-Hinshelwood mechanism with a good linear fit. Photocatalysts synthesized using anatase TiO2 were reported with improved performance compared to rutile phase. It is evident that synthesis parameters influence photocatalyst performance directly. The higher rate constant (> 1) that proves the excellent adsorption capacity of the tested photocatalysts for tested pollutants on the surface may have a great prospective for photocatalytic water purification at neutral pH.

Evaluation, of the bimetallic photocatalytic performance of Resin–Au–Pd nanocomposite for degradation of parathion pesticide under visible light

In this work, Pd-Au nanoparticles supported on Amberlyst® resin (Pd-Au/Amberlyst®) as bimetallic photocatalyst with super adsorption performance, plasmonic effect, and fast interfacial charge migration was synthesized. The nano photocatalyst was characterized by FT-IR, ICP, XRD, FESEM, EDS mapping analysis, and TEM. Photocatalytic degradation under visible light of parathion as an organophosphorus pesticide by Pd-Au/Amberlyst® nanocomposite was studied. UV–Vis absorption spectroscopic technique studies were employed to investigate the performance of the nanocatalyst. This nanocatalyst has several fascinating advantages including easy preparation method, good catalytic activity, environmentally benign reaction conditions and was recovered with no considerable decrease in activity, it could be reused 6 times without obvious decrease in the yield of reactions.

Excellent fabrication of Pd-Ag NPs/PSi photocatalyst based on bimetallic nanoparticles for improving methylene blue photocatalytic degradation

A Pd-Ag nanoparticles (NPs)/macro porous silicon (macroPSi) hetero structure based on plasmonic bimetallic photocatalyst was used to improve the activity of the methylene blue (MB) degradation. The Pd-Ag NPs/macroPSi photocatalyst efficiency was compared with that of the as-prepared macroPSi, Ag NPs/macroPSi and Pd NPs/macroPSi hetero structures to study the effect of Schottky alone and on the synergistic effect of Schottky and plasmonic. The modification of macroPSi was carried out through deposition of monometallic and bimetallic NPs of Ag and Pd, via simple immersion process. The structural properties of the photocatalysts were examined by scanning electron microscopy (SEM), x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS). The influence of monometallic and bimetallic NPs on the Photocatalytic activity was tested under ultraviolet light illumination. The results showed that the Photocatalytic activity of Pd-Ag NPs/macroPSi photocatalyst is higher than that of as-prepared macroPSi, Ag NPs/macroPSi, Pd NPs/ macroPSi photocatalysts. The maximum Photocatalytic efficiency of (98.8%) and a degradation rate of (0.033 min−1) were obtained by using Pd-Ag NPs/macroPSi photocatalyst.

Hydrogen‐Generating Ru/Pt Bimetallic Photocatalysts Based on Phenyl‐Phenanthroline Peripheral Ligands

Recent studies on hydrogen-generating supramolecular bimetallic photocatalysts indicate a more important role of the peripheral ligands than expected, motivating us to design a Ru/Pt complex with 4,7-diphenyl-1,10-phenanthroline peripheral ligands. Photoinduced intra- and inter-ligand internal conversion processes have been investigated using transient absorption spectroscopy, spanning the femto- to nanosecond timescale. After photoexcitation and ultrafast intersystem crossing, triplet states localised on either the peripheral ligands or on the bridging ligand/catalytic unit are populated in a non-equilibrated way. Time-resolved photoluminescence demonstrates that the lifetime for the Ru/Pt dinuclear species (795±8 ns) is significantly less than that of the mononuclear analogue (1375±20 ns). The photocatalytic studies show modest hydrogen turnover numbers, which is possibly caused by the absence of an excited state equilibrium. Finally, we identify challenges that must be overcome to further develop this class of photocatalysts and propose directions for future research.

Coordinative integration of copper (II) and iron (II) phthalocyanine into amidoximated PAN fiber for enhanced photocatalytic activity under visible light irradiation

Metal phthalocyanine (MPc) complexes hold great promise for photocatalysis applications because of their high visible light harvesting efficiency and semiconductive properties. However, the effective development requires the suppression of their rapid charge recombination. Transition metal ions can act as electron traps to enhance the charge separation of semiconductors, but challenges still remain for bimetallic co-catalysis of MPc due to the difficulties in the combination between them. Herein, we proposed a new approach to enable the assisted metal ions to interact with MPc through fibrous support, constructing a novel bimetallic photocatalyst via simultaneously immobilizing iron(II) phthalocyanine (FePc) and Cu(II) onto the surface of amidoximated polyacrylonitrile (PAN) fiber. Taking the photodegradation of organic dyes as model reactions, this bimetallic catalyst achieves much higher photoactivity than that of the monometallic FePc catalyst, and effectively converts surface H2O2 into hydroxyl radicals rather than superoxide radicals and high-valent metal-oxo species. The Cu(II) not only enables the transfer of photoexcited electrons from FePc, but also promotes the running of Fe(II)/Fe(III) cycle to boost reactive radicals generation through H2O2 activation. The strategy of coupling Cu(II) with MPc through fibrous support provides a facile and promising solution for the advancement of MPc-based photocatalysis via visible light energy.

Photocatalytic Degradation of 4-Nitrophenol Under Natural Sunlight with Ti-Zn Bimetallic Photocatalyst

Photocatalytic Degradation of 4-Nitrophenol Under Natural Sunlight with Ti-Zn Bimetallic Photocatalyst