Photocathodic Protection Properties Research Articles

Enhancing photocathodic protection performance by controlled synthesis of Bi/BiOBr/TiO2 NTAs Z-scheme heterojunction films

A novel method for the synthesis of bismuth (Bi) nanospheres on the surface of BiOBr/TiO2 nanocomposites is presented, which can be used for controllable preparation of BiOBr/TiO2 and Bi/BiOBr/TiO2 heterojunction films. The synthesis temperature of the one-pot glycol-assisted solvothermal method is the key factor affecting the formation of Bi nanospheres and the loading of BiOBr nanosheets. The structural and optical properties of the films were characterized, and the photocathodic protection property of the prepared photoanodes under different solvothermal temperatures was systematically investigated. The reason for enhancing the photocathodic protection performance of Bi/BiOBr/TiO2 photoanode by introducing Bi nanospheres was also explained, and it was found that the photoanode prepared at 160 °C has the best performance. Under visible light illumination, the Bi/BiOBr/TiO2 photoanode can negatively shift the potential of coupled 316 L stainless steel to ‐430 mV (vs. SCE). The durability tests demonstrated the excellent photochemical stability and good scouring resistance of the Bi/BiOBr/TiO2 photoanode. Moreover, a charge transfer mechanism for Z-scheme heterojunctions was proposed based on the electron spin resonance characterization results of the Bi/BiOBr/TiO2 photoanode. The formation of Z-scheme heterojunctions is mainly attributed to that the Bi nanospheres play a "bridge" role between BiOBr and TiO2, which realizes the Z-scheme electron transport mechanism in the Bi/BiOBr/TiO2 films.

Preparation of lotus-root-typed TiO2 nanotubes by NH4F/KF based electrolyte and its efficient photocathodic protection for 304 stainless steel

A highly ordered lotus-root-typed TiO2 nanotube array (TNTAs) was prepared by two-step electrochemical anodization in a novel NH4F/KF-based electrolyte. The effects of different morphologies of TiO2 nanotubes on the photoelectrochemical properties of TNTAs were studied. The photoelectrochemical properties of TNTAs were evaluated by measuring the photocurrent density-time curve. The photocathodic protection performance of TNTAs on 304 stainless steel was evaluated by measuring open circuit potential and Tafel curve. The results showed that the TNTAs with lotus-root-type porous structures prepared at 20 V had the optimal photoelectric chemical properties and photocathodic protection properties. Under simulated sunlight, the maximum photocurrent density can reach 306.7 μA·cm−2, and the lowest open circuit potential can reach -0.987 V (vs Ag/AgCl).

Drastic promotion of the photocathodic protection property of TiO2 nanotube films decorated with n-type CuInS2 nanoparticles

The n-type CuInS2 nanoparticles were deposited successfully on n-type TiO2 nanotube surface via the successive ion layer absorption and reaction (SILAR) technique. Compared with the pure TiO2, the photoresponse of CuInS2/TiO2 films is expanded to the visible region, indicating an excellent visible light utilization rate and improved photoelectric conversion efficiency. Benefiting from the favorable n-n heterojunction structure, the photocurrent density of CuInS2/TiO2 photoanode under visible light irradiation exceeded 40 μA/cm2, which was 8 times that of the TiO2. The potential of the coupled 316L stainless steel in 3.5 wt% NaCl aqueous solution was droped by − 850 mV in the presence of CuInS2/TiO2 films, which showed a remarkable photocathode protection performance of n-n type CuInS2/TiO2 heterojunction materials.

Photoelectrochemical Cathodic Protection of Stainless Steel using W- and Cr-Doped/Codoped TiO2 Nanotube Thin Film Photoanodes

TiO2 nanotubes have been co-doped with chromium and tungsten by electrochemical anodization. Tungsten and chromium single doped and pure TiO2 nanotubes have also been synthesized. Many methods have been used to characterize the products obtained. Following doping and co-doping of TiO2, the optical absorption edges are considerably red shifted to the visible region due to the induced impurity states within the band gap. The samples prepared were used as photoanodes for photocathodic protection in order to retard 403 stainless steel corrosion. Chromium and tungsten co-doping was found to enhance the visible photocatalytic activity of the resulting TiO2 nanotubes. Better photoelectrochemical performance and photocathodic protection properties were shown by (Cr-W)-co-doped TiO2, Cr-doped TiO2 and W-doped TiO2 samples compared with the undoped TiO2 nanotubes. The best co-doped TiO2 sample showed a photocurrent density, which was 2.6 times higher than that of the undoped TiO2. Under light illumination, the (Cr-W)-co-doped TiO2 photoelectrode decreased the potential of the coupled 403 stainless steel in a 3.5 wt. % NaCl solution to 400 mV, indicating an effective photocathodic protection. The synergetic effects of co-doping by chromium and tungsten may be responsible for the enhanced visible photocatalytic activity.

A novel CaIn2S4/TiO2 NTAs heterojunction photoanode for highly efficient photocathodic protection performance of 316 SS under visible light

Designing heterojunction photocatalysts with matched band structure and good interface contact is an effective method to improve the photoelectrochemical activity. Herein, novel CaIn2S4/TiO2 nanotube arrays (NTAs) heterojunction photoanodes were successfully prepared by electrochemical anodization and hydrothermal method. The microstructures, compositions, crystal structures, chemical valence states and light absorption performances of the composites were evaluated by field emission scanning electron microscopy, energy dispersive x-ray spectroscopy transmission electron microscope, high-resolution transmission electron microscope, x-ray diffractometer, x-ray photoelectron spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), respectively. The photocathodic protection performances of CaIn2S4/TiO2 composites for 316 stainless steel (SS) and the influences of the CaIn2S4 content on the performances were studied. The microstructural examination revealed the uniform doping of CaIn2S4 nanofragments on the TiO2 NTAs, and the composite was made up cubic CaIn2S4 and anatase TiO2. The photogenerated electrons were transferred from the TiO2 to CaIn2S4 at the interface of the composite. Compared with pure TiO2 NTAs, CaIn2S4/TiO2 NTAs exhibited better photocathodic protection performance for 316 SS under visible light. Potential drop reached 0.78 V versus saturated calomel electrode for the 316 SS coupled with CaIn2S4/TiO2 NTAs. The photocurrent density of the 316 SS coupled with the composite photoanode (235.4 μA cm–2) was 17.4 times that of TiO2. The improved photocathodic protection property of CaIn2S4/TiO2 NTAs was ascribed to the enhanced separation efficiency of the photogenerated carriers and the strong visible light absorption of the material. The CaIn2S4/TiO2 NTAs exhibited continuous protection of the 316 SS for more than 12 h even in the dark. Therefore, the CaIn2S4/TiO2 NTAs heterojunction composite is an outstanding and efficient photoanode for the photocathodic protection of metals.

Preparation and Photocathodic Protection Properties of ZnO/TiO2 Heterojunction Film Under Simulated Solar Light.

In this work, a novel double layer made of ZnO nanorod arrays and TiO2 nanorod arrays with anticorrosion function were successfully prepared on fluorine-doped tin oxide (FTO) substrate by a simple low-temperature solvothermal method. As compared with the pure TiO2 and pure ZnO film, the combination of the two films presented higher photocathodic protection performance for 316 stainless steel (316 SS) and Q235 carbon steel in 3.5 wt% NaCl solution. The composite film with ZnO nanoparticles layer between ZnO nanorod arrays and TiO2 nanorod arrays exhibited the best photocathodic performance, which lowered the open circuit potential (OCP) of 316 SS and Q235 to −991 mV, −1066 mV, respectively. The results demonstrated that the formation of the uniform heterojunction film and the small difference in band alignment played important roles in the promotion of photocathodic protection performance.

Preparation of various boron-doped TiO2 nanostructures by in situ anodizing method and investigation of their photoelectrochemical and photocathodic protection properties

Boron (a metalloid) has been chosen as the doping agent in the titanium dioxide structure via in situ anodizing method in this work. FE-SEM, XPS, Raman spectroscopy, XRD, EDX and UV–visible techniques were used to investigate the morphology, structure and optical properties of the samples prepared. XPS and UV–visible techniques were used to confirm the presence of boron in the nanotubes and the reduction in band gap, respectively. Afterward, the impact of the concentration of the doping agent on the photoelectrocatalytic and anticorrosion properties of the nanotubes was studied through different electrochemical techniques such as linear sweep voltammetry, chronoamperometry, open-circuit potential and Tafel under visible light. Better photocatalytic performance and anticorrosion properties are shown by nanotubes modified by boron compared with bare titanium dioxide nanotubes, according to the results. The photo-response increases dramatically as boric acid concentration in anodizing electrolyte is increased from samples BT1 to BT10 and slowly decreases for samples BT10-BT25. The best photoelectrocatalytic performance in photoelectrochemical water splitting studies was shown by samples BT10 and BT15. Ultimately, the photo-generated cathodic protection of 403 stainless steel (403SS) has been studied in a corrosion cell using a 3.5% NaCl solution under visible light by the photocatalysts prepared. The photocatalytic activity of TiO2 under visible light illumination was enhanced by doping of boron, based on the results.

3D ZnIn2S4 nanosheets/TiO2 nanotubes as photoanodes for photocathodic protection of Q235 CS with high efficiency under visible light

A 3-dimensional ZnIn2S4/TiO2 nanotubes composite was prepared by a combined hydrothermal reaction and electrochemical anodization method. Photogenerated open circuit potential, photogenerated current density, electrochemical impedance spectra, Tafel curves, and i-V curves were measured to investigate the photoelectrochemical activities and photocathodic protection properties for Q235 carbon steel. The results showed that the photocurrent density of the ZnIn2S4/TiO2 composite was greatly increased compared with pure TiO2. Under visible light irradiation, the photocurrent density of the ZnIn2S4-0.25/TiO2 composite can reach 400 μA cm−2, which was two times that of TiO2. The photogenerated potential drop of the composite photoanode was about 0.36 V, which was greater than that of TiO2 (about 0.16 V). The introduction of the ZnIn2S4 improved the visible light absorption ability and photogenerated charge separation efficiency of TiO2. The loading of ZnIn2S4 onto the TiO2 surface led to a negative shift of the Fermi level of TiO2. The generation of adsorbed oxygen can facilitate the separation of photogenerated charges.

Preparation and photocathodic protection property of ZnIn2S4/RGO/TiO2 composites for Q235 carbon steel under visible light

For improving the photocathodic protection performance of TiO2 photoanode, ZnIn2S4/reduced graphene oxide (RGO)/TiO2 nanotubes (NTs) composite was synthesized by electrochemical anodizing combined with hydrothermal method. The photoelectrochemical and photocathodic protection properties of the ZnIn2S4/RGO/TiO2 composite were investigated in detail. Compared with pure TiO2 NTs, the ZnIn2S4/RGO/TiO2 composite showed a significant improvement in photocathodic protection performances. The photogenerated open circuit potential drop of ZnIn2S4/RGO/TiO2 coupled with Q235 carbon steel in 3.5 wt% NaCl solution under visible light could reach 420 mV versus saturated calomel electrode, which was more than twice as much as that of pure TiO2. The photogenerated current density of ZnIn2S4/RGO/TiO2 could reach 5.6 mA cm−2, which was twice as much as that of pure TiO2. The appearance of the adsorbed oxygen (OA) enabled the ZnIn2S4/RGO/TiO2 to have better photo-carrier separation efficiency and better photogenerated cathodic protection than pure TiO2. The present work demonstrated ZnIn2S4/RGO/TiO2 could be a potential material for photoanodes because of its better visible-light response, higher electrical conductivity and smaller charge transfer resistance.

Nanoflower like SnO2-TiO2 nanotubes composite photoelectrode for efficient photocathodic protection of 304 stainless steel

In this study, titanium dioxide nanotube arrays (TiO2-NTs) were prepared on titanium plates through a two-step anodization method and then the SnO2 nanoparticles were deposited onto TiO2-NTs by electrodeposition method to produce SnO2-TiO2-NTs. The electrodeposition time has a great influence on the photoeletrochemical (PEC) performance of SnO2-TiO2-NTs composite photoelectrode. The photocurrent density of SnO2-TiO2-NTs electrode increased up to 4 times as compared to pristine TiO2-NTs photoelectrode. Furthermore, open circuit potential and tafel curves were measured to evaluate the photocathodic protection properties of SnO2-TiO2-NTs. The corrosion potential dropped to -730 mV and the corrosion current density reached to 259.8 μA/cm−2. The results indicate that SnO2 deposition into the TiO2-NTs photo-electrode is a simple and effective way to protect stainless steel (304SS) from corrosion.

ZnFeAl-layered double hydroxides/TiO2 composites as photoanodes for photocathodic protection of 304 stainless steel

A series of ZnFeAl-layered double hydroxides/TiO2 (ZnFeAl-LDHs/TiO2) composites are synthesized by a combined anodization and hydrothermal method. The structure, surface morphology, photo absorption and photocathodic protection properties of these samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) and electrochemical tests. The unique structure of the ZnFeAl-LDHs reduces the charge carriers recombination, and the visible photoresponse property increase the light harvesting. The XPS study reveals that the electrons in the ZnFeAl-LDHs travel to TiO2, and the ZnFeAl-LDHs/TiO2 composites generate and transfer more electrons to 304 stainless steel (304SS), and exhibits a better photocathodic protection performance than pure TiO2. In addition, after intermittent visible-light illumination for four days, the photoanode still exhibits good stability and durability.

Synthesis and Photocathodic Protection Properties of Nanostructured SnS/TiO2 Composites

SnS/TiO2 nanocomposites were successfully fabricated by a successive ionic layer adsorption and reaction process. The effect of the material concentration on the preparation of the SnS/TiO2 composite films was discussed. TiO2 nanotube arrays co-sensitized with SnS nanoparticles were used as a photoanode to provide photoelectric protection for 304 stainless steel. The crystalline structures, morphology, and optical absorption property of the samples were measured by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The photo-generated cathodic protection performance was characterized by measuring the open-circuit potential and photocurrent density response, and by performing electrochemical impedance spectroscopy. The results indicate that the SnS/TiO2 composites have high light absorption and photo-electrochemical properties under visible light irradiation. The SnS/TiO2 composite prepared at the optimal concentration could shift the corrosion potential of the 304 stainless steel form −280 mV to −720 mV.

Preparation and photocathodic protection property of Ag2S-TiO2 composites

The Ag2S-TiO2 composites with good photocathodic protection performance for 304 stainless steel have been investigated here. The effects of different kinds of sulfur sources on this photocathodic protection property were also examined. TiO2 nanotubes were prepared by two-step electrochemical anodization. And Ag2S was loaded on the TiO2 nanotubes through a hydrothermal method. The morphology, crystal structure, elemental composition and light absorption capability of the samples were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) analyses. The performances of cathodic protection were evaluated by the electro-chemical methods including open-circuit potential, photocurrent density and Tafel polarization curves. Results indicated that the Ag2S-TiO2 composites exhibited great enhancement of the light absorption and photo-electrochemical property under visible light illumination. The morphology and distribution of the samples have some effects on photocathodic protection properties of 304 stainless steel and the Ag2S-TiO2 composite with sodium sulfide as sulfur source showed the optimal performance.

Preparation of NiO/TiO2p-n heterojunction composites and its photocathodic protection properties for 304 stainless steel under simulated solar light

The NiO/TiO2p-n heterojunction composites were synthesized by electroless plating and annealing, which resulted in TiO2 nanotube arrays coated with a layer of NiO particles. The morphology, composition, and structure of NiO/TiO2p-n heterojunction composites were corroborated by scanning electron microscopy, X-ray diffraction, FT-IR spectra, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectroscopy. The influences of electroless plating time and annealing temperature on the photoelectrochemical performance of the composites were investigated, and their photocathodic protection performance for 304SS under visible light irradiation were also evaluated in 3.5% NaCl solution through open-circuit potential, photoresponse spectra, and Tafel polarization curves. NiO/TiO2 heterojunction composites prepared under optimum conditions induce considerable enhancement of light absorption and exhibit excellent photoelectrochemical performance, which provide better photocathodic protection for 304SS.

Enhancement of photoelectrochemical and photocathodic protection properties of TiO2 nanotube arrays by simple surface UV treatment

A simple and efficient surface treatment method toward practical applications to enhance photo response of TiO2 nanotube arrays (NTs) photoelectrode was reported. TiO2 NTs were prepared by two-step electrochemical anodization methods, following by surface ultra violet light (UV) illumination treatment, which can produce amounts of hydroxyl groups on the surface of TiO2 NTs photoelectrode. The photoelectrochemical measurements demonstrate that the photocurrent density of the UV treated TiO2 NTs photoelectrode enhances by 50% than that of the pristine TiO2 NTs photoelectrode. More interestingly, the decayed photocurrent density of TiO2 NTs can recover the high value by illumination treatment again after using/storing for several days. Additionally, open circuit potential, tafel curves and electrochemical impedance spectroscopy measurements exhibit that the UV illumination treatment for TiO2 NTs photoelectrode is an easy and effective strategy to protect 304 stainless steel from corrosion by photogenerated cathode protection.

Preparation of NiSe2/TiO2 nanocomposite for photocathodic protection of stainless steel

NiSe2 nanoparticles are used to modify highly-ordered TiO2 nanotube film as photoanode, and its photocathodic protection performance for 304 stainless steel is investigated. TiO2 nanotube film on Ti foil is fabricated via the anodic oxidation, and the deposited NiSe2 on its surface is prepared by electrochemical deposition with different cyclic voltammetry cycles. Compared to pure TiO2, NiSe2/TiO2 nanocomposites exhibits increasing photoelectro-response activity and photocathodic protection performance for 304 stainless steel under visible light illumination. The photocathodic protection property of NiSe2/TiO2 is affected by the amount of deposited NiSe2 on TiO2 nanotubes film, and the specimen with 2-cycle deposition exhibits an optimal photocathodic protection property.

Characterization and photoelectrochemical performance of Zn-doped TiO2 films by sol–gel method

Zn-doped TiO2 (Zn–TiO2) thin films were prepared by the sol–gel method on titanium substrates with heat treatment at different temperatures. The effects of heat treatment temperatures and Zn doping on the structure, photocathodic protection and photoelectrochemical properties of TiO2 thin films were investigated. It is indicated that the photoelectrical performance of the Zn–TiO2 films is enhanced with the addition of Zn element compared with the pure-TiO2 film and the largest decline by 897 mV in the electrode potential is achieved under 300 °C heat treatment. SEM–EDS analyses show that Zn element is unevenly distributed in Zn–TiO2 films; XRD patterns reveal that the grain size of Zn–TiO2 is smaller than that of pure-TiO2; FTIR results indicate that Zn—O bond forms on Zn–TiO2 surface. Ultraviolet visible absorption spectra prove that Zn–TiO2 shifts to visible light region. Mott–Shottky curves show that the flat-band potential of Zn–TiO2 is more negative and charge carrier density is bigger than that of pure-TiO2, implying that under the synergy of the width of the space-charge layer, carrier density and flat-band potential, Zn–TiO2 with 300 °C heat treatment displays the best photocathodic protection performance.

304不锈钢表面ZnO/TiO 2 复合薄膜的制备与光生阴极防腐蚀性能研究

ZnO/TiO2 composite film was prepared on the surface of 304 stainless steel by sol-gel technique and spin coating method. The phase composition and microstructure of the as-prepared ZnO/TiO2 composite film was characterized by X-ray diffraction (XRD) and scanning electron mi- croscope (SEM), respectively. The effect of the preparation procedure and calcination temperature on the photoelectric property has been investigated and the photocathodic protection performance of such composite film for 304 stainless steel was also evaluated in 3.0%NaCl solution by using the electrochemical method. The results indicate that the composite film prepared by two-step proce- dure with proper calcination temperature exhibits excellent photo- electrochemical performance. The photocathodic protection property of ZnO/TiO2 composite film for 304 stainless steel under UV light illumination is significantly superior to that of pure TiO2 film and ZnO film respectively.

Photocathodic Protection of TiO2 Composite Material on 304 Stainless Steel

TiO2 and other semiconductor materials were found to have photocathodic protection effect for the metal coupled with these semiconductors film, as the potential of the metal shifted to a more negative value than its corrosion potential and the corrosion of the metal was prevented. TiO2 has been one of the most important semiconductors because of its good environmental friendliness and chemical stability. However, due to the wide band gap of TiO2 (3.2 eV) and the recombination of the photogenerated electron-hole (e–-h+) pairs, it can only absorb the light with the wavelength less than 380 nm, and it is hard to maintain the cathodic protection in the dark. In this paper, CdSe and other materials were applied to improve the photocathodic protection property. TiO2 nanotubes was prepared by anodization method, and CdSe was deposited on the TiO2 nanotube arrays by cyclic voltammetry method, and the optimum condition was selected from different cycles. The surface morphology and crystal phase of the composite was investigated by scanning electron microscopy (SEM), X ray diffraction (XRD) method. The photocathodic protection property of the composite material for 304 stainless steel in seawater was investigated by the electrochemical method including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and the tafel polarization curves method. The experimental results showed that open circuit potential of 304 stainless steel decreased from -190mV to -500mV when the light was turned on, and the electrode potential slowly rises to about -250mV after the light was turned off. The composite material still could maintain the protective effect on stainless steel after the light was turned off. The work was supported by the Project of National Development and Reform Commission, the Nantong Science Project (BK2014008), and National Basic Research Program of China (2014CB643304).

CdTe and graphene co-sensitized TiO2 nanotube array photoanodes for protection of 304SS under visible light

CdTe/graphene/TiO2 films that served as photoanodes for cathodic protection application were prepared by an electrochemical deposition method. The deposition of graphene and CdTe nanoparticles (NPs) on the surface of the TiO2 nanotubes was confirmed by scanning electron microscope and transmission electron microscopy. The composites exhibited high light absorption in both the UV and visible light region. The results indicated that TiO2 nanotube photoelectrodes sensitized by 20-cycle graphene and 30-cycle CdTe NPs exhibited effective photocathodic protection properties for 304 stainless steel (304SS) under the visible-light illumination, with an photopotential of −750 mV versus saturated calomel electrode and a current density of 560 μA cm−2. Due to the efficient photogenerated charge separation, the three-component CdTe/graphene/TiO2 showed stronger photoresponse than pure TiO2 under visible-light illumination. In summary, the CdTe/graphene could improve the photocathodic protection properties of TiO2 films.