Photocorrosion Inhibition Research Articles

Probing effective photocorrosion inhibition and highly improved photocatalytic hydrogen production on monodisperse PANI@CdS core-shell nanospheres

CdS is a very good visible-light responsive photocatalyst for hydrogen production. However, the fast recombination of photogenerated electron-hole pairs and quick photocorrosion limit its application in photocatalysis. To address these problems, we herein have designed and synthesized monodisperse polyaniline@cadmium sulfide (PANI@CdS) core-shell nanospheres to probe the mechanisms of photocorrosion inhibition and photocatalytic H2 production. All the PANI@CdS core-shell nanospheres demonstrate highly enhanced photocorrosion inhibition and photocatalytic hydrogen production comparing to the pure CdS nanospheres. Particularly, the PANI@CdS core-shell nanospheres with the thinnest PANI shell possess the highest hydrogen production rate of 310μmolh−1g−1 in 30h without deactivation. Our results reveal that the newly formed CS and/or NCd bonds in PANI@CdS prevent the reduction of the surface sulfide ions to sulphur, leading to effective photocorrosion inhibition. Our results also verify that the photogenerated holes migrating from valence band (VB) of CdS to the highest occupied molecular orbital (HOMO) of PANI leads to the enhanced photocatalytic hydrogen production. This work can shed some light on the mechanism of conducting polymers modifying metal sulfides for effective photocorrosion inhibition and highly enhanced photocatalytic activities.

The synthesis of elegant hierarchical CdS via a facile hydrothermal method assisted by inorganic salt, with photocorrosion inhibition

We report an environmentally friendly hydrothermal method assisted by inorganic salt for controlling the shape of CdS nanostructure. First, we make aqueous solution of NaCl to fabricate CdS via a hydrothermal reaction at 160 °C, 12 h. Afterward, the outcomes of CdS change from nanosphere to hierarchically flower-like structure, with a higher concentration of NaCl solution. Further investigation reveals improved stability of flower-like CdS photocatalyst for water treatment.

Ultrasound assisted synthesis of ZnO/reduced graphene oxide composites with enhanced photocatalytic activity and anti-photocorrosion

A method to improve the photocatalytic activity and suppress the photocorrosion of ZnO was developed by depositing ZnO nanoparticles onto the surface of reduced graphene oxide (rGO) via in situ growth with ultrasound assisted synthesis. The optimum synergetic effect of ZnO/rGO composite was found at a weight ratio of 2% (rGO/ZnO). Compared with ZnO, the photocatalytic activities of ZnO/rGO composite for the degradation of methylene blue (MB) and C.I. acid red 249 (AR249) aqueous solutions under UV light irradiation were increased by 8.6% and 14.7%, respectively. The improved photocatalytic activity was originated from the rapid separation of photogenerated electrons and holes on the interface of rGO and ZnO. The photocorrosion of ZnO was inhibited obviously after hybridization with rGO. Even after six successive cycles under UV irradiation, the photocatalytic activities of ZnO/rGO composite for MB and AR249 still retained 92.9% and 94.8% of that for the first cycling run, while that of ZnO obviously decreased due to serious photocorrosion. The photocorrosion inhibition of ZnO by rGO was attributed to the reduced activation of surface oxygen atom on the surface of ZnO.

Photo-corrosion inhibition of Ag3PO4 by polyaniline coating

In this paper, polyaniline-coated silver phosphate has been successfully prepared via a facile chemisorption method in order to improve the stability of Ag3PO4 under light irradiation. The crystalline phase, band gap energy, and microstructure of the obtained PANI/Ag3PO4 composites were characterized by X-ray diffraction, UV–vis diffuse reflection spectroscopy, scanning electron microscopy, and transmission electron microscopy, respectively. The photocatalytic degradation of methlylene blue was performed to test the activities of PANI/Ag3PO4 composites with different coating amounts and the results indicate that the stabilities of PANI/Ag3PO4 composites were successfully enhanced. The correlation between photocatalytic performance and the properties of PANI/Ag3PO4 composites is discussed in detail.

The encapsulation of CdS in carbon nanotubes for stable and efficient photocatalysis

A CdS encapsulated carbon nanotube (CNT) photocatalyst was prepared by a liquid-chemistry method. Through filling of CNTs with CdS, the aggregation of CdS was prevented efficiently by the good confinement effect of CNTs, and the photocatalytic performance of CdS was enhanced by 2.5 times via synergistic integration of the confinement effect of CNTs and heterojunction between CNTs and CdS. The photostability of CdS encapsulated in and attached on CNTs was investigated systematically through methylene blue photocatalytic degradation, X-ray diffraction, transmission electron microscopy, and inductively coupled plasma-atomic emission spectroscopy. The results indicate that the photocorrosion of CdS is successfully suppressed when it is encapsulated in the CNTs. The mechanism analysis suggests that spatial synergy of the CdS and powerful adsorptivity of CNTs are the primary causes for photocorrosion inhibition. Our efforts propose a new scheme to remarkably promote both the photostability and photocatalytic activity of photocorrosion-susceptible photocatalysts.

Inhibition of photocorrosion and photoactivity enhancement for ZnO via specific hollow ZnO core/ZnS shell structure

Hollow ZnO core/ZnS shell structure (ZnO/ZnS HCSS) has been successfully synthesized via a microwave-assisted hydrothermal approach. It is found that such a ZnO/ZnS HCSS exhibits higher photocatalytic activity than pure ZnO and ZnS toward the liquid-phase degradation of methyl orange (MO) under UV irradiation. What is more noteworthy, it is also demonstrated that ZnO/ZnS HCSS photocatalyst overcomes the photocorrosion in comparison to pristine ZnO by mean of cycling tests toward MO. The detailed degradation process of MO over ZnO/ZnS HCSS is investigated by liquid chromatography–mass spectrometry method. And then, the roles of active species in the photocatalytic process are discussed by using different types of active species scavengers. Meanwhile, combined with the electron spin resonance and photocurrent test, the degradation mechanism of the photocatalysts is proposed. It is hoped that the work could provide valuable information on the design of specific structure materials with more excellent properties and set the foundation for the further industrial application.

Perfect inhibition of CdS photocorrosion by graphene sheltering engineering on TiO2 nanotube array for highly stable photocatalytic activity.

An artful graphene sheltering engineering onto TiO2 nanotube array for perfect inhibition of CdS photocorrosion (RGO/CdS-TiO2 NT) has been developed by a one-step electrodeposition method. The CdS photocorrosion driven by both holes and radicals has been systematically investigated and identified. The RGO layer provides a perfect protection to CdS through (i) blocking the attack of active species especially ˙OH radicals and (ii) offering a closed electron-rich microenvironment where the stored electrons RGO(e(-)) not only reduce intermediate species S˙(-) to S(2-) but also compensate the valence band of CdS for its loss of electrons to alleviate CdS photocorrosion from oxidation by holes. The photocatalyst exhibits extremely high stability. RGO/CdS-TiO2 NT shows high visible-light photocatalytic activity for the degradations of organic dye methylene blue (MB), industrial chemical p-nitrophenol (PNP) and herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). This work provides a new insight into the protection of photosensitive semiconductors from photocorrosion.

Inhibition of pyrite corrosion and photocorrosion by MEKF-R modified carbazoles

In this study natural iron sulfide (FeS2) surface was coated by films of poly(N-vinylcarbazole) (PNVCz), poly(N-vinylcarbazole methylethylketoneformaldehyde resin) (P[NVCz-MEKF-R]), carbazole methylethylketone formaldehyde resin (Cz-MEKFR) and poly(carbazole methyl ethylketone formaldehyde resin) (P[Cz-MEKFR]). The corrosion, photocorrosion, and photoactivity characteristics of coated electrodes were investigated in potassium iodide/iodide (KI/I2) redox electrolyte. The inhibition effect and photoactivity of Cz-MEKF-R, P[Cz-MEKF-R] P[NVCz-MEKFR] and PNVCz homopolymer coatings were compared. Coating performance was tested by polarization and electrochemical impedance (EIS) measurements. The photopotential and photocurrent values of bare and coated pyrite electrodes were obtained under illuminated conditions. The inhibition efficiencies were calculated from corrosion currents obtained by Tafel extrapolation from polarization curves.

ZnO photonic crystals with enhanced photocatalytic activity and photostability

ZnO photonic crystals (ZnO-PCs) with large area and high quality were prepared by a facile auto-forced impregnation method. The resulting ZnO-PCs exhibited remarkable photocatalytic performance and photocorrosion inhibition compared with porous and commercial nanoparticle ZnO.

Mesoporous Fe-doped TiO2 sub-microspheres with enhanced photocatalytic activity under visible light illumination

Mesoporous Fe-doped TiO2 sub-microspheres (m-Fe-TMS) with high surface area, accessibility, and crystallinity were prepared using a rapid and continuous aerosol-assisted self-assembly (AASA) process for visible-light photocatalytic degradation of persistent pharmaceuticals. The results of X-ray absorption near-edge structure (XANEX) spectroscopy indicate that iron exists as octahedrally coordinated Fe3+ ions substituting Ti4+ in the TiO2 lattice. The similarity of the Fe/Ti ratios in the bulk and on the surface, as determined by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS), reveals that the substitution of Ti4+ by Fe3+ ions uniformly occurs within m-Fe-TMS. UV–vis diffuse reflectance spectroscopy shows that m-Fe-TMS exhibits a shift in the absorption threshold toward the visible spectrum. Under visible light irradiation, m-Fe-TMS exhibits a maximum rate of pharmaceutical photodegradation four times that of m-TMS. The photocatalytic degradation rates are reproducible with m-Fe-TMS, even after 10 repeated runs. The formation of chemical FeOTi bonds, and not of isolated Fe2O3 particles, leads to the inhibition of photocorrosion and leaching in the photocatalytic reactions. The ease and scalable production of m-Fe-TMS using the AASA process will facilitate the development of visible light-driven photocatalysts for decomposition of environmental contaminants.

A New Approach for Photocorrosion Inhibition of Ag2CO3Photocatalyst with Highly Visible-Light-Responsive Reactivity

A novel visible-light-responsive photocatalyst Ag2CO3 was prepared by a facile precipitation reaction between NaHCO3 and AgNO3. The as-prepared samples showed relatively high photocatalytic activity toward rhodamine B (RhB) degradation in aqueous solution. The observed photoreactivity on Ag2CO3 was attributed to the synergetic effects of small band gap, great oxidation potential of photogenerated holes, and high separation efficiency of photogenerated electrons and holes. Nevertheless, Ag2CO3 was unstable under visible light due to the photocorrosion resulting from metallic silver formation. The photocorrosion of Ag2CO3 can be efficiently inhibited by adding AgNO3 in the photocatalytic reaction system owing to the lower electrode potential of Ag/AgNO3 than that of Ag/Ag2CO3. Our results shed new light on the photocatalytic activity as well as photocorrosion mechanism of silver-containing compounds and inhibit the method of photocorrosion.

Photo-corrosion inhibition and photoactivity enhancement with tailored zinc oxide thin films

The nanocrystalline ZnO, TiO2 and ZnO/TiO2 films are deposited onto FTO-coated glass substrates by using spray pyrolysis technique. The structural, morphological, optical and photoelectrochemical properties of the ZnO, TiO2 and ZnO/TiO2 are investigated by X-ray diffraction, scanning electron microscopy, UV–Vis spectroscopy and photoelectrochemical techniques. XRD analysis shows that films are polycrystalline and having hexagonal and tetragonal crystal structure for pure ZnO and TiO2. The photocatalytic degradation of methylene blue has been investigated with ZnO, TiO2 and ZnO/TiO2 photocatalysts. ZnO/TiO2 thin films have proved quite effective mineralization of methylene blue, while pure ZnO and TiO2 do not lead complete mineralization of methylene blue. The metabolites produced during degradation are analyzed by HPLC and Fourier transforms infrared spectroscopy. The by-products detected during degradation have been identified by GCMS technique.

Enhancement of photocurrent and photocatalytic activity of ZnO hybridized with graphite-like C3N4

A ZnO photocatalyst was hybridized with graphite-like C3N4via a monolayer-dispersed method. After hybridization with C3N4, the photocurrent of ZnO was enhanced by 5 times under UV irradiation and a photocurrent under visible light irradiation was observed. The photocatalytic activity of C3N4/ZnO under UV irradiation was increased by 3.5 times, the visible light photocatalytic activity was generated and the photocorrosion of ZnO was suppressed completely after ZnO was hybridized with C3N4. The enhancement in performance and photocorrosion inhibition under UV irradiation was induced by the high separation efficiency of photoinduced holes from ZnO to the HOMO of C3N4. Under visible light irradiation, the electron excited from the HOMO to the LUMO of C3N4 could directly inject into the CB of ZnO, making C3N4/ZnO present visible light photocatalytic activity. The optimum synergetic effect of C3N4/ZnO was found at a weight ratio of 3%, which corresponded to a monolayer dispersion of C3N4 on the surface of ZnO.

Inhibiting corrosion of n-GaAs by cetylpyridinium chloride for stabilised photoelectochemical cell

The cationic surfactant cetylpyridinium chloride (CPC) provides photocorrosion inhibition to the GaAs surface when CPC is chemisorbed on the GaAs surface from aqueous acidic electrolytes at concentrations of CPC lower than its critical micelle concentration (CMC). In the presence of CPC, the anodic photogenerated current which is originally due to oxidising the n-GaAS electrode decreases, essentially, due to the adsorption of CPC on the n-GaAs surface. The presence of CPC in the electrolyte also shifts the onset potential of the photocurrent towards more negative values; this is also explained by adsorption of the surfactant molecule on GaAs surface, presumably, via its pyridine aromatic ring. In addition, CPC adsorption not only affects the electrochemical properties of the GaAs electrode but also substantially decreases the rate of photocorroion of GaAs. Photocorrosion is investigated by measuring the quantities of dissolved arsenic and gallium ions into the electrolyte by inductively coupled plasma mass spectroscopy. This dissolution results in an enriching the GaAS surface by gallium due to the referential dissolution of arsenic ions. The maximum inhibition efficiency due to the addition of CPC to the electrolyte is about 80%. Upon addition of cerous nitrate to the acidic solution of CPC the anodic photocurrent is stable and does not exhibit significant change over time though the rate of dissolving the electrode material stays low. It is concluded that in the presence of added Ce3+ the photocurrent is generated due to the oxidation of Ce+3 ions rather than the oxidation of the electrode material itself.

Photocorrosion Inhibition and Photoactivity Enhancement for Zinc Oxide via Hybridization with Monolayer Polyaniline

Monomolecular-layer polyaniline (PANI) was dispersed on the surface of zinc oxide (ZnO) and formed the hybrid effect between ZnO and PANI. The hybrid photocatalysts showed dramatic photocatalytic activity for the degradation of the methylene blue (MB) both under ultraviolet and visible light irradiation, and the photocorrosion of ZnO was successfully inhibited. The enhanced photocatalytic activity for PANI-hybridized ZnO originated from the high separation efficiency of photogenerated electrons and holes on the interface of PANI and ZnO, which was produced by the hybrid effect of PANI and ZnO. The photocorrosion inhibition of ZnO could be attributed to the rapidly transferring of photogenerated holes by the PANI monolayer. The relationship between the PANI content of the samples and their photocatalytic performance shows that an optimal PANI weight percent (1.0%) can significantly enhance the photocatalytic efficiency and anticorrosion of ZnO particles. In particular, the mechanisms on the enhancement of ...

Photocorrosion Inhibition and Enhancement of Photocatalytic Activity for ZnO via Hybridization with C60

C60 molecules with monomolecular layer state dispersed on the surface of ZnO and formed the hybridized interaction between ZnO and C60. C60-hybridized ZnO photocatalyst showed enhanced photocatalytic activity for the degradation of the organic dye and the photocorrosion of ZnO was successfully inhibited bythe hybridization of C60 molecules. The photocorrosion inhibition of ZnO by C60 molecule could be attributed to the reduced activation of surface oxygen atom. The enhanced photocatalytic activity for C60-hybridized ZnO was originated from the high migration efficiency of photoinduced electrons on the interface of C60 and ZnO, which was produced by the interaction of C60 and ZnO with a conjugative pi-system. The enhancement degree of photocatalytic activity was strongly depended on the coverage of C60 molecules on the surface of ZnO nanoparticles, and the optimum hybridization effect was found at a weight ratio of 1.5% (C60/ZnO). The hybridization of C60 with semiconductors could be used to improve the photocatalytic activity as well as the photostability.

Photocorrosion inhibition -ofn-GaAs in acidified aqueous iodide solution

AbstractThe photocorrosion of n-GaAs electrodes in aqueous solutions represents one of the most important factors limiting their application in solar energy conversion. In continuation of previous studies, the corrosion of n-GaAs has been investigated in 0·5M H2SO4 using a pllOtoelectrochemical cell. Illumination of the n-GaAs anode with white light of intensity 20 mW cm-2 generated a saturation photocurrent of 27 mA cm-2 at biasing voltages more positive than +0·45 V(SCE). This current corresponded to hydrogen discharge at the platinum counter electrode and to oxidation of the GaAs surface. When 0·01-6·0M LiI was added to the H2SO4 solution, 12 was formed at the n-GaAs electrode and dissolved in the iodide solution. The onset potential of the photocurrent (Ep) shifted from -0·36 to -0·73 V(SCE) as the concentration was varied from 0·01 to 6·0M I-. Addition of I-3 shifted Ep to more positive values. The extent of corrosion was studied by comparing the ratios of photogenerated I2 and H2. In 0·01, 1·0, and ...

Photocorrosion inhibition -ofn-GaAs in acidified aqueous iodide solution

Photocorrosion inhibition -of<i>n</i>-GaAs in acidified aqueous iodide solution

Photoresponse of indium hexacyanoferrate

Abstract Formation of insoluble metal hexacyanoferrate films on chalcogenide semiconductor materials in ferrocyanide medium has been found to be responsible for enhanced photocurrents and inhibition of photocorrosion. Similar beneficial properties recorded by us for the first time on indium hexacyanoferrate in ferrocyanide medium and explained in terms of formation of surface films of composites involving iron hexacyanoferrates are described in this paper.

Cleavage of Water by Visible‐Light Irradiation of Colloidal CdS Solutions; Inhibition of Photocorrosion by RuO2

The conversion of light into chemical fuels in photochemical devices equipped with semiconductor electrodes (e.g. of n‐CdS) is associated with a serious problem: “holes” produced in the valence band of the semidonductor upon irradiation migrate to the surface where photocorrosion occurs. In mi‐croheterogenous CdS systems this is remedied by a thin layer of RuO2. A CdS sol prepared in the presence of maleic anhydride/styrene copolymer has now been loaded with RuO2 and Pt; these CdS microelectrodes are surprisingly active catalysts for cleavage of H2O and H2S.