Photodeposition Method Research Articles

Fabrication of Ag/RP composite with excellent photocatalytic activity for degrading high concentration of methyl orange solution

A series of ultra-low content of Ag decorated red phosphorus (Ag/RP) composites were fabricated by a simple photo-deposition method and were characterized by XRD, UV–Vis, SEM, TEM, BET, EDS and XPS. The results showed that Ag/RP displayed excellent photocatalytic activity for degrading high concentration of methyl orange solution (MO, 50 mL, 50 mg/L) under visible light (λ > 420 nm). The ultra-low content of Ag largely enhanced the activity of RP due to the strong separation efficiency of photocarriers, ensured by the transient photocurrent responses (TPR) and electrochemical impedance spectra (EIS). This result guides us to design highly efficient photocatalyst for removal of high concentrations of waste waters under visible light.

Photodeposition of Au Nanoclusters for Enhanced Photocatalytic Dye Degradation over TiO2 Thin Film.

Au nanoparticle (NP) decorated heterogeneous TiO2 catalysts are known to be effective in the degradation of various organic pollutants. The photocatalytic performance of such Au-TiO2 structures remarkably depends on the size, morphology, and surface coverage of the Au NPs decorating TiO2. Here we propose an effective way of preparing a highly active Au nanocluster (NC) decorated TiO2 thin film by a novel photodeposition method. By altering the solvent type as well as the illumination time, we achieved well-controlled surface coverage of TiO2 by Au NCs, which directly influences the photocatalytic performance. Here the Au NCs coverage affects both the electron store capacity and the optical absorption of the hybrid Au-TiO2 system. At low surface coverage, 19.2-29.5%, the Au NCs seem to enhance significantly the optical adsorption of TiO2 at UV wavelengths which therefore leads to a higher photocatalytic performance.

Photocatalytic degradation of organophosphorus pesticide using semiconductor-sensitized composite in natural water: effect of oxidants

In this work, dichlorvos was degraded with photocatalytically active n-type semiconductors and p–n junction-type semiconductors. The p–n junction-type semiconductors such as GO–TiO2 (GO = graphene oxide) and GO–WO3 were synthesized by photodeposition method using commercial TiO2 and WO3. GO-doped nano-TiO2 was synthesized through sol–gel technique from titanium(IV) isopropoxide by hydrothermal treatment. The synthesized materials were characterized by different techniques such as XRD, UV, FTIR, SEM and TEM. In order to find out the photocatalytic ability towards degradation of dichlorvos, the experiment was carried out in an aqueous suspension under UV light in the presence of oxygen and oxidants such as H2O2 and K2S2O8. From the evaluation, GO–nano-TiO2 with H2O2 was found to be highly active that showed complete degradation of dichlorvos within 15 min under UV light.

The Improvement of Coralline-Like ZnGa2O4 by Cocatalysts for the Photocatalytic Degradation of Rhodamine B

To date, various methods have been used to synthesize ZnGa2O4 material to promote photodegradation performance. However, cocatalysts, which usually play a crucial role in the photocatalyst system, have not been studied extensively in photocatalytic degradation reactions. In this paper, ZnGa2O4 semiconducting material was synthesized by a traditional high-temperature solid-state reaction. The as-prepared powder was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet–visible diffused reflectance spectroscopy. The results indicate that the as-prepared sample is a highly crystallized granular sample with a bandgap of 4.44 eV and a uniform particle size distribution. Density functional theory (DFT) was utilized to calculate the electronic structure of ZnGa2O4. The valence bands and conduction bands were chiefly composed of O 2p atomic orbitals and the hybridization orbitals of Ga 4s4p and Zn4s4p, respectively. The photocatalytic performance was tested via the decomposition of rhodamine B (RhB) under the irradiation of ultraviolet light. Cu, Ag, Au, Ni, Pt, and Pd cocatalysts were loaded on the ZnGa2O4 photocatalyst by a photodeposition method. The relatively optimal cocatalyst of ZnGa2O4 in the photocatalytic degradation reaction is Au. Thereafter, the effect of loading different usage amounts of the Au cocatalyst for the photodegradation of the ZnGa2O4 photocatalyst was studied in detail. The experimental results displayed that the optimum photodegradation activity was confirmed with the 3 wt% Au/ZnGa2O4 sample, which was 14.1 times more than the unloaded photocatalyst. The maximum photocatalytic degradation ratio of RhB was 96.7%, with 180 min under ultraviolet light.

Accelerated Semihydrogenation of Alkynes over a Copper/Palladium/Titanium (IV) Oxide Photocatalyst Free from Poison and H2 Gas

AbstractSelective hydrogenation of alkynes to alkenes (semihydrogenation) without the use of a poison and H2 is challenging because alkenes are easily hydrogenated to alkanes. In this study, a titanium (IV) oxide photocatalyst having Pd core‐Cu shell nanoparticles (Pd@Cu/TiO2) was prepared by using the two‐step photodeposition method, and Pd@Cu/TiO2 samples having various Cu contents were characterized by electron transmission microscopy, X‐ray photoelectron spectroscopy and UV‐vis spectroscopy. Thus‐prepared Pd@Cu/TiO2 samples were used for photocatalytic hydrogenation of 4‐octyne in alcohol and the catalytic properties were compared with those of Pd/TiO2 and Cu/TiO2. 4‐Octyne was fully hydrogenated to octane over Pd/TiO2 at a high rate and 4‐octyne was semihydrogenated to cis‐4‐octene over Cu/TiO2 at a low rate. Rapid semihydrogenation of 4‐octyne was achieved over Pd(0.2 mol%)@Cu(1.0 mol%)/TiO2, indicating that the Pd core greatly activated the Cu shell that acted as reaction sites. A slight increase in the reaction temperature greatly increased the rate with a suppressed rate of H2 evolution as the side reaction. Changes in the reaction rates of the main and side reactions are discussed on the basis of results of kinetic studies. Reusability and expandability of Pd@Cu/TiO2 in semihydrogenation are also discussed.

Colour centre controlled formation of stable sub-nanometer transition metal clusters on TiO2 nanosheet for high efficient H2 production

The transition elements (Fe, Co, Ni) are important substitutes for noble metals as the co-catalysts in hydrogen evolution reaction. Enhancing the atom utilization efficiency is highly desirable, but preparation and preservation of the transition metal catalysts with the size downscaling to sub-nanometer are challenging. In this work, Fe, Co and Ni clusters with subnano size as co-catalysts are synthesized by controllable growth on 2D ultrathin TiO2(B) nanosheets for hydrogen evolution using a photo deposition method. The ultra-small Fe, Co, and Ni co-catalysts on the TiO2(B) nanosheets exhibit remarkably enhanced photo activities, compared to that with the best Pt loading. It is found that the oxygen bridge vacancies act as the colour centres locating at the position adjacent to the O1-Ti1 sites on the TiO2(B) (0 0 1) surface. The photo-colouration and photo-bleaching have significantly impact on the nucleation and growth of the metallic clusters. The high density and uniform dispersion of the sub-nano-sized transition metal clusters benefits for the photo reduction under light irradiation, as well as efficient carrier separation, leading to a great improvement of the photo activity.

Electric fields and local magnetic field enhance Ag-BiVO4-MnOx photoelectrochemical and photocatalytic performance

The Ag-BiVO4-MnOx multi-stage interface heterojunction photocatalyst is prepared via photo-deposition method. The oxidation co-catalyst MnOx and reduction co-catalyst Ag are selectively deposited onto (0 1 0) and (1 1 0) facets of BiVO4. Under ultraviolet (UV) light, MnOx is deposited onto the BiVO4 (1 1 0) facet, causing its energy band to move upward and bend at the interface to produce a p-n junction and a built-in electric field that points from BiVO4 towards MnOx. Simultaneously, the difference in energy levels allows the BiVO4 to form surface heterojunction and produce a built-in electric field that points from (0 1 0) facet towards the (1 1 0) facet. A Schottky junction is formed when Ag is deposited onto the BiVO4 (0 1 0) facet to create space charge region without free carriers. A built-in electric field is formed that points from Ag to BiVO4. The electric fields generated via light excitation and a local magnetic field formed by plasmonic Ag improve the photocatalytic activity of the Ag-BiVO4-MnOx photocatalyst, the degradation rate of Ag-BiVO4-MnOx is 5.9 times higher than that of the BiVO4. This work not only promotes the separation efficiency of photogenerated charge carriers, but also pays attention to the synergistic effect of electric fields generated by light excitation and local magnetic field formed by plasmonic Ag, which provides a new idea for photocatalysis research.

Atomic Platinum Anchored on Fe‐N‐C Material for High Performance Oxygen Reduction Reaction

Development of highly active and stable catalysts to reduce the amount of Pt or replace Pt with nonprecious transition metal in acid of oxygen reduction reaction (ORR) is still an enormous challenge. Herein, we report anchoring atomic Pt particles on Fe/N‐doped carbon material (Pt1.1FeNC) are, for the first time, synthesized by the photodeposition method. The obtained Pt1.1FeNC electrocatalyst exhibits superior electrocatalytic activity and good stability for four‐electron oxygen reduction reaction (ORR) in an acidic electrolyte. Pt1.1FeNC electrocatalyst shows a half‐wave potential of 0.85 V vs. reversible hydrogen electrode (RHE) in 0.1 m HClO4 (0.83 V of 20 wt.‐% commercial Pt/C). After 10,000 cycles after, the catalysis active only decreases 20 mV. These are mainly due to the synergistic effect between Pt and Fe.

Preparation of a NiO/KNbO3 nanocomposite via a photodeposition method and its superior performance in photocatalytic N2 fixation

A p-NiO/n-KNbO3 heterojunction photocatalyst was synthesized via a photodeposition method and for the first time applied in photocatalytic N2 fixation under simulated sunlight.

Comparison of platinum photodeposition processes on two types of titanium dioxide photocatalysts.

The photodeposition method is useful for the preparation of metal-loaded photocatalysts, by which the metal precursors are adsorbed on the photocatalyst surface and reduced by photoexcited electrons to typically form metallic nanoparticles. In the present study, the photodeposition process of Pt nanoparticles was investigated on anatase and rutile TiO2 photocatalysts. It was found that on the anatase surface, only some of the Pt4+ precursors were first adsorbed in an adsorption equilibrium and reduced to form a smaller number of initial metal species; then, they functioned as electron receivers to reduce the remaining precursors on their metallic surfaces and become larger particles. In contrast, the rutile surface can adsorb most of the precursors and quickly reduce them upon photoirradiation to form nanoparticles, giving a larger number of small nanoparticles. As a result, the Pt-loaded rutile photocatalyst exhibited higher activity in hydrogen evolution from an aqueous methanol solution than the Pt-loaded anatase photocatalyst.

Surface state modulation for size-controllable photodeposition of noble metal nanoparticles on semiconductors

The size distributions of noble metals on semiconductors can be precisely controlled by the photodeposition method with modulated surface states.

Photodeposition fabrication of hierarchical layered Co-doped Ni oxyhydroxide (NixCo1−xOOH) catalysts with enhanced electrocatalytic performance for oxygen evolution reaction

Highly active, durable and inexpensive oxygen evolution reaction (OER) catalysts are crucial for achieving practical and high-efficiency water splitting. Herein, hierarchical interconnected NixCo1−xOOH nanosheet arrays supported on TiO2/Ti substrate have been fabricated through a facile photodeposition method. Compared with pristine NiOOH, the obtained NixCo1−xOOH nanosheet arrays possess larger exposed electrochemical active surface area, faster transfer and collection of electrons and stronger electronic interaction, showing a low overpotential of 350 mV at a current density of 10 mA·cm−2 and a small Tafel slope of 41 mV·dec−1 in basic solutions, with the OER performance superior to pristine NiOOH and most Ni-based catalysts. Furthermore, the NixCo1−xOOH electrode demonstrates excellent stability at the current density of 10 mA·cm−2 for 24 hours, which is attributed to the structural maintenance caused by the good adhesion of the catalyst and the substrate. Our study provides an alternative approach for the rational design of highly active and promising OER electrocatalysts.

P-Type Cu2O as an effective interlayer between CdS and NiOx cocatalysts to promote photocatalytic hydrogen production

A two-step photodeposition method is introduced, aiming to construct a p-type Cu2O interlayer between n-type CdS and NiOx cocatalyst. The effect of Cu2O interlayer is supposed to accelerate the hole transfer from CdS.

Effect of Dual-Cocatalyst Surface Modification on Photodegradation Activity, Pathway, and Mechanisms with Highly Efficient Ag/BaTiO3/MnOx.

Cocatalyst surface-loading has been regarded as an effective strategy to promote solar-energy-conversion efficiency. However, the potential influence of surface modification with cocatalysts on the photodegradation pathway and the underlying mechanisms is still unclear. Herein, we have used ferroelectric BaTiO3 as the substrate, and both the reduction cocatalyst Ag and the oxidation cocatalyst MnOx have been successfully loaded onto BaTiO3 simultaneously by a one-step photodeposition method as evidenced by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The influence of dual-cocatalyst surface-loading on photodegradation of rhodamine B has been systematically investigated for the first time. First, the dual-cocatalyst-modified BaTiO3 outperformed over the single-cocatalyst-loaded BaTiO3, and the photodegradation rate of Ag/BaTiO3/MnOx is about 3 times and 12 times as high as that of Ag/BaTiO3 and BaTiO3/MnOx, respectively. The credit is given to the synergistic effect between the reduction and oxidation cocatalysts, prompting charge carrier separation and migration as verified by the transient photocurrent, electrochemical impedance, and photoluminescence (PL) spectrum investigation. Second, in addition to the boosted photodegradation activity, the photodegradation pathway is found to be altered as well when using Ag/BaTiO3/MnOx. High-performance liquid chromatography (HPLC) analysis indicated that a highly selective stepwise deethylation process predominates over chromophore cleavage in the Ag/BaTiO3/MnOx system, while it is reverse for the Ag/BaTiO3 system. This phenomenon is attributed to the different dye molecule adsorption modes. Furthermore, the radical trapping experiment shows that holes play a major role in the degradation process, and the recycle test proves the excellent stability of Ag/BaTiO3/MnOx. Our findings may add another layer of understanding depth to cocatalyst surface modification in photodegradation applications.

Novel direct dual Z-scheme AgBr(Ag)/MIL-101(Cr)/CuFe2O4 for efficient conversion of nitrate to nitrogen

Photocatalytic reduction of nitrate has attracted much attention recently, however, low efficiency and difficult separation have limited its application in practice. In this study, the novel direct dual Z-scheme AgBr(Ag)/MIL-101(Cr)/CuFe2O4 (AB/M/CFO) was fabricated by the hydrothermal technology combined with the photodeposition method for the first time. The AB/M/CFO exhibited the highest nitrate conversion and nitrogen selectivity (79.9% and 94.5%, respectively) compared to AgBr(Ag)/MIL-101(Cr), MIL-101(Cr) and CuFe2O4 for 30 min UV-light irradiation. The dual Z-scheme of AB/M/CFO enhanced electron transfer and charge separation, which was proved by transient photocurrent responses, leading to a significant improvement in photocatalytic efficiency. Meanwhile, after four cycles, the AB/M/CFO photocatalyst also displayed a strong magnetic separation ability and excellent recycling stability. Furthermore, the excitation and electron transfer process over dual Z-scheme AB/M/CFO photocatalytic material were proposed, based on the radical trapping experiments. Our work provides a new strategy to construct dual Z-scheme MOFs-based materials that have promising applications in photocatalytic reduction of pollutants.

Morphological effect of 1D/1D In2O3/TiO2 NRs/NWs heterojunction photo-embedded with Cu-NPs for enhanced photocatalytic H2 evolution under visible light

Well-designed Cu-loaded 1D/1D In2O3 NRs/TiO2 NWs heterojunction for photocatalytic H2 production under visible light has been investigated. In-situ synthesis of In2O3 NRs anchored over TiO2 NWs were obtained through hydrothermal approach, while Cu-NPs were loaded using photo-deposition method. Maximum H2 evolution of 4390 ppm g-cat−1 h−1 was achieved over Cu-In2O3 NRs/TiO2 NWs heterojunction which is 4.2 and 7.8 folds higher than using In2O3 NRs/TiO2 NWs and TiO2 NWs, respectively. Morphological effects revealed 3.92 folds higher H2 production over Cu-In2O3 NRs/TiO2 NWs compared to nanoparticles. The significantly enhanced H2 evolution was because of 1D/1D heterojunction with a good interaction between composite materials for faster charge separation. Among all the sacrificial reagents, glycerol found more proficient for H2 production due to the presence of more α-H atoms attached to carbon atoms. Quantum yield (QY) of 0.675% was obtained over Cu-In2O3 NRs/TiO2 NWs composite, which is ∼4 folds higher than using the same composite with nanoparticles. This reveals structure of materials greatly contributed for utilizing photon flux for the production of charge carriers with their faster separation. Thus, a good metal-support interaction could provide an efficient pathway for solar energy assisted hydrogen production and can be used for other solar fuel applications.

In vivo removal of radioactive cesium compound using Prussian blue-deposited iron oxide nanoparticles.

Aim: To mitigate the side effects of medical treatment by Prussian blue (PB), a well-known adsorbent for radioactive cesium (Cs), PB-deposited magnetic nanoparticles (MNPs), were prepared and analyzed on the adsorbent capacity for Cs removal. Materials & methods: The PB-deposited MNPs were prepared by photo-deposition method and investigated for their Cs adsorption properties in vitro and in vivo. The distribution of the adsorbents was also evaluated in C57BL/6 mice. Results: PB-deposited MNPs provided an improved adsorbent capacity for Cs removal and reduced toxicity to blood cells compared with those of bulk PB. Conclusion: PB-deposited MNPs could be considered as an alternative of PB-based medicine to reduce the possible hazards caused by high dose of PB intake.

A simple and effective synthesis of magnetic γ-Fe2O3@SiO2@TiO2–Ag microspheres as a recyclable photocatalyst: dye degradation and antibacterial potential

In this study, an effective technique for synthesizing γ-Fe2O3@SiO2@TiO2-Ag magnetically separable photocatalyst was introduced by combining co-precipitation, sol-gel, and photo-deposition methods. A series of analyses including FTIR, SEM, EDS, XRD, and VSM were applied to characterize the prepared materials and the investigations on photocatalytic activity of the prepared composites were accomplished. Compared to bare γ-Fe2O3@SiO2@TiO2, the Ag-doped composite was more active in terms of photocatalytic characteristics. By applying γ-Fe2O3@SiO2@TiO2-Ag, the decomposition rate of the Basic blue 41 reached to about 94% after 3h of UV irradiation; this rate was 63% for pure γ-Fe2O3@SiO2@TiO2. The results indicated that the dye degradation kinetics followed first-order kinetic model. During the five cycles of separation, it was observed that the Ag-doped composite was greatly effective and stable in terms of recycling. Moreover, the results indicated that antibacterial activity of γ-Fe2O3@SiO2@TiO2-Ag was remarkably stronger than that of pure Fe2O3@SiO2@TiO2 particles. It was concluded that by modifying magnetic TiO2 by silver nanoparticles, charge separation was eased by catching photo-generated electrons, resulted in an enhanced photo- and biological activity. Graphical abstract.

Promotion of photocatalytic steam reforming of methane over Ag0/Ag+-SrTiO3

Methane (CH4) is not only used as a fuel but also as a promising clean energy source for hydrogen generation. The steam reforming of CH4 (SRM) using photocatalysts can realize the production of syngas (CO + H2) with low energy consumption. In this work, Ag0/Ag+-loaded SrTiO3 nanocomposites were successfully prepared through a photodeposition method. When the loading amount of Ag is 0.5 mol%, the atom ratio of Ag+ to Ag0 was found to be 51:49. In this case, a synergistic effect of Ag0 and Ag+ was observed, in which Ag0 was proposed to improve the adsorption of H2O to produce hydroxyl radicals and enhance the utilization of light energy as well as the separation of charge carriers. Meanwhile, Ag0 was regarded as the reduction reaction site with the function of an electron trapping agent. In addition, Ag+ adsorbed the CH4 molecules and acted as the oxidation reaction sites in the process of photocatalytic SRM to further promote electron-hole separation. As a result, 0.5 mol% Ag-SrTiO3 exhibited enhancement of photocatalytic activity for SRM with the highest CO production rate of 4.3 μmol g−1 h−1, which is ca. 5 times higher than that of pure SrTiO3. This work provides a facile route to fabricate nanocomposite with cocatalyst featuring different functions in promoting photocatalytic activity for SRM.

Photo-deposition of ZnO/Co3O4 core-shell nanorods with p-n junction for efficient oxygen evolution reaction

Co3O4 has attracted extensive interests as a non-noble-metal electrocatalyst of oxygen evolution reaction, which is critical to many electrical energy conversion and storage devices; however, conductivity has impeded further improvement to its catalysis activity. Herein, ZnO/Co3O4 core-shell nanorods are fabricated on Ni foil by a mild photo-deposition method to accelerate charge transfer between Co3O4 and the conductive substrate. The mild prepare method effectively avoids the oxidation of Ni foil and constructs p-n heterojunction between ZnO and Co3O4. Compared with sole Co3O4, the ZnO/Co3O4 core-shell nanorods exhibit larger electrochemical active surface area and smaller charge transfer resistance. Besides, the XPS results reveal that the strong electron interaction on nanointerfaces induces electronic structure modulation, which may bring interfacial charge transfer from Co to Zn, and further cooperate synergistically toward the oxygen generation in alkali solution. Moreover, the electrochemical active surface area of the ZnO/Co3O4 nanorods varies with the photo-deposit time and influences the OER performance. When the photo-deposit time is 4 h, the as-fabricated ZnO/Co3O4 nanorods exhibit excellent electrochemical performance with overpotential of 294 mV at 10 mA cm−2, Tafel slope of 49 mV dec−1, and outstanding stability for oxygen evolution reaction in alkaline medium.