•MnO2/TiO2 NTAs was fabricated by electrodeposition process.•MnO2/TiO2 NTAs exhibited superior physicochemical properties.•Effect of fabricating parameters on PC degradation of pollutants was studied.•The enhanced visible PEC mechanism of MnO2/TiO2 NTAs was proposed.MnO2/TiO2 nano-tube arrays (MnO2/TiO2 NTAs) photoelectrode was synthesized through anodization and electrodeposition, followed by the prepared conditions optimized. Subsequently, structures of the as-prepared photoelectrodes were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Besides, the light absorption capacities and photoelectrochemical (PECH) properties were investigated through UV–vis diffuse reflectance spectrophotometer (UV–vis DRS), photocurrent response (PCR) and electrochemical impedance spectroscopy (EIS). In addition, these photoelectrodes were used for the photoelectrocatalytic (PEC) degradation of methylene orange (MO) under Xenon lamp irradiation. Moreover, the enhanced PEC mechanism was further confirmed through scavengering effect and photoluminsecence (PL) spectra. Results presented that the highly ordered TiO2 nano-tube arrays photoelectrodes processed a uniform sizes of inner diameter of 300 nm and well thickness of 60 nm with MnO2 nanoparticles successfully deposited. Furthermore, it was found that these novel MnO2/TiO2 NTAs photoelectrodes could not only red-shift the light absorption to visible region between 400 nm and 700 nm, but also significantly enhance the generation of hydroxyl radicals (OH) which played an important role in the PEC system. Noticeably, the MnO2/TiO2 NTAs photoelectrodes made in the optimized conditions exhibited much higher PEC activity toward MO degradation with the efficiency up to 95.2% within 1 h when external potential (+2.0 V) was applied. More importantly, these novel MnO2/TiO2 NTAs photoelectrodes proved to have excellent stability and reusability that would have great potentials for organic contaminants degradation in wastewater treatment.Download high-res image (190KB)Download full-size image

•Ag2O/TiO2-Zeolite composite was fabricated through modified sol-gel process.•Ag2O/TiO2-Zeolite exhibited higher photoinduced charge separation efficiency.•Ag2O/TiO2-Zeolite composite displayed high PC performance.•PC degradation pathways of norfloxacin was proposed and confirmed.Norfloxacin, as an antimicrobial drug, has frequently been detected in municipal plants, which is predicted to be potential risk on human beings and the environment. In the present study, zeolite immobilizes silver oxide decorated titanium dioxide (Ag2O/TiO2-Zeolite) composite has been fabricated through modified sol-gel method. Afterwards, physicochemical properties of the as-fabricated Ag2O/TiO2-Zeolite sample are systematically studied by scanning electron microscope, X-ray diffraction, X-ray photoelectron microscopy, ultraviolet visible diffuse reflectance spectroscopy and surface photovoltage spectra measurements. Besides these, photocatalytic (PC) performance of Ag2O/TiO2-Zeolite composite is evaluated by photodecomposition of norfloxacin under simulated solar light illumination and generation of active hydroxyl (OH) radicals. Results indicate that the decorated Ag species exists in the form of Ag2O, which can greatly enhance the visible light absorbance and charge separation efficiency. Furthermore, Ag2O/TiO2-Zeolite composite displays superior PC performance, which is mainly ascribed to the intense light absorbance in visible region, narrow band gap level and high charge separation efficiency. In addition, the solar light PC degradation pathways of norfloxacin are proposed according to the HPLC-MS/MS measurements, including hydroxylation addition to parent compound, decarboxylation and defluorination of side chain from the norfloxacin. Moreover, the as-fabricated Ag2O/TiO2-Zeolite composite exhibits high stability after consecutive utilization for seven times.Download high-res image (80KB)Download full-size image

•Ag-Ag2O/r-TiO2 photocatalyst was fabricated through solution reduction strategy.•Ag-Ag2O/r-TiO2 exhibited higher photoinduced charge separation efficiency.•Contribution of each species to the degradation of diclofenac was distinguished.•The enhanced visible light driven (VLD) PC mechanism was confirmed in detail.In this study, Ag-Ag2O/reduced TiO2 (denoted as Ag-Ag2O/r-TiO2) nano-photocatalyst had been fabricated through one-step solution reduction strategy in the presence of potassium borohydride. Afterwards, physicochemical properties of the resulting samples were investigated by scanning electron microscope (SEM), N2 adsorption/desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV-vis DRS), electron spin resonance (ESR) and time-resolved surface photovoltage (TR-SPV) techniques. Results indicated that potassium borohydride treatment could simutaneously induce the generation of Ti3+ self-doping energy level between the forbidden band of TiO2 and metallic Ag species existed in the forms of Ag0 and Ag2O nanocrystalline, thereby resulting in the greatly enhanced visible light absorbance and photoinduced charge separation efficiency. In addition, the visible light driven (VLD) photocatalytic (PC) performance was evaluated through the degradation of diclofenac and generation of ·OH radicals. As-expected, Ag-Ag2O/r-TiO2 sample exhibited higher VLD PC performance and larger generation amount of ·OH radicals. Furthermore, the enhanced VLD PC mechanism was proposed and confirmed, which was mainly attributed to the synergistic effect originated from the localized SPR of Ag0 nanocrystalline and Ti3+ self-doping which responsible for the intense visible light absorbance, high photoinduced charge separation efficiency and VLD PC performance.Download high-res image (120KB)Download full-size image

•NVZI/TiO2 NTAs photoelectrode was fabricated by electrodeposition process.•NZVI/TiO2 NTAs photoelectrode exhibited higher photoinduced charge separation efficiency.•The enhanced visible light responsible PC mechanism was proposed.In this study, nano-scale zero-valent iron (NZVI) decorated TiO2 nano-tube arrays (NZVI/TiO2 NTAs) photoelectrode was fabricated through anodization process, followed by galvanostatic electrodeposition strategy. Afterwards, physicochemical properties of the resulting NZVI/TiO2 NTAs samples were systematically studied by SEM, XRD, XPS, UV–vis DRS and photoelectrochemical (PECH) measurements. Results indicated that NZVI/TiO2 NTAs photoelectrode exhibited greatly enhanced visible light absorbance and high photogenerated charge separation efficiency. However, after photocatalytic (PC) reaction, NVZI particles were converted to α-Fe2O3 species, which would further improve the visible light absorbance and PC efficiency, which was confirmed by the further enhanced visible light PC performance for decomposition of 4-chlorphenol (4-CP) and generation of OH radicals. Furthermore, the enhanced visible light mechanism of NZVI/TiO2 NTAs photoelectrode was detailed discussed. This study provides a versatile strategy to fabricate high-efficient catalysts which could be used in the high-toxic and refractory micro-pollutants elimination in water body.Download high-res image (208KB)Download full-size image

•NiO/TiO2 NTAs photoelectrode has been fabricated through electrodeposition process.•NiO/TiO2 NTAs photoelectrode exhibited high PC performance for decomposition of 4-CP.•The enhanced visible light PC mechanism was proposed.In the study, we report that p-type NiO (p-NiO) nanoparticles were successfully decorated onto the surface of n-type TiO2 nano-tube arrays (n-TiO2 NTAs) photoelectrode by anodization process, followed by electrodeposition strategy in the presence of NiSO4 electrolyte. After then, the samples were studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). In addition, the optical and photoelectrochemical (PECH) properties of p-NiO/n-TiO2 NTAs were recorded through ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) curves, respectively. Furthermore, We evaluated the photocatalytic (PC) degradation of 4-chlorphenol and the enhanced PC mechanism was also discussed. Results suggest that p-NiO/n-TiO2 NTAs photoelectrode exhibited higher PC activities than that of pristine TiO2 NTAs owing to its higher photogeneration electrons-holes (e/h+) pairs separation efficiency and light absorbance. As a consequence, the p-NiO/n-TiO2 NTAs photoelectrode could be applied in degradation of organic pollutants and wastewater purification.Download high-res image (152KB)Download full-size image

•Ag2O/reduced TiO2 NTAs photoelectrode was fabricated by microwave reduction strategy.•Ag2O/reduced TiO2 NTAs photoelectrode exhibited high charge separation efficiency.•Ag2O/reduced TiO2 NTAs photoelectrode displayed high PC performance.•The enhanced visible light PC mechanism was proposed.In order to improve the charge separation and photocatalytic (PC) efficiency of TiO2 nano-tube arrays (TiO2 NTAs) photoelectrode, narrower band gap Ag2O nano-crystallites decorated reduced TiO2 NTAs (Ag2O/r-TiO2 NTAs) photoelectrode was fabricated through one-step microwave reduction strategy, which could simultaneously induce the generation of Ag2O nano-crystallites onto the surface of TiO2 NTAs and Ti3+ self-doping energy level below the conduction band of TiO2. Subsequently, the resulting photoelectrodes were systematically studied by scanning electron spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–visible light diffuse reflectance spectroscopy and photoelectrochemical measurements. In addition, the photocatalytic (PC) performance was evaluated by photodecomposition of methyl blue and generation of OH radicals. As a result, Ag2O/r-TiO2 NTAs photoelectrode performed a significantly enhanced light absorbance in the whole visible region, transient photocurrent density of 0.189 mA cm−2, photoinduced charge separation efficiency and 98.9% of PC efficiency for decomposition of methyl blue. Furthermore, the enhanced visible light PC mechanism for decomposition of organic pollutant was proposed, which was mainly attributed to the strong visible light absorbance and high photoinduced charge separation efficiency. Moreover, the as-fabricated Ag2O/r-TiO2 NTAs photoelectrode performed well stability after consecutive utilization for five cycles. This study provides a versatile strategy to fabricate high-efficient catalyst which could be utilized in waste water elimination.Download high-res image (142KB)Download full-size image

•TiO2 NRs/NSs was fabricated by hydrothermal reaction in an alkaline condition.•Calcination temperature was crucial to control PECH properties of TiO2 NRs/NSs.•TiO2 NRs/NSs exhibited high PC activity for decomposition of methylene blue.•TiO2 NRs/NSs photoelectrode displayed high charge separation efficiency.•TiO2 NRs/NSs photoelectrode performed well stability after seven cycles.In the study, Using the strategy of hydrothermal reaction followed by annealing at different temperatures, TiO2 nanorods/nanosheets (NRs/NSs) photoelectrodes with diverse microcosmic morphologies and crystal structures were successfully fabricated. Moreover, all samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and Ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). Meanwhile the photoelectrochemical (PECH) properties were recorded through open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) curves. The photocatalytic (PC) activity of TiO2 NRs/NSs photoelectrodes were further measured by methylene blue (MB) degradation. Results suggest that the nanosheets possessed the width and thickness in the range of 100–400 and 10–20 nm, and the nanorods possessed the diameter in the range of around 10–20 nm, respectively. Also, the TiO2 NRs/NSs photoelectrode calcined at 500 °C exhibited the best proportion of both nanosheets and nanorods and higher photocatalytic activity (73.56%) than those of other TiO2 NRs/NSs photoelectrodes within 150 min under visible light illumination, which was ascribed to higher photoproduction electrons-holes (e/h+) pairs separation and visible light absorption. Therefore, the calcination temperature plays a significant role in altering the morphology and crystal structure of TiO2 NRs/NSs photoelectrode, and then enhanced PC performance.Download high-res image (130KB)Download full-size image

•Ag/AgBr plasma was fabricated through solution reduction strategy.•Ag/AgBr plasma exhibited higher photoinduced charge separation efficiency.•Ag/AgBr plasma displayed high visible light PC performance.•The enhanced visible light PC mechanism was confirmed in detail.•PC degradation pathways of acetaminophen was proposed and confirmed.In the present work, plasmonic Ag/AgBr nano-particle was fabricated by solution reduction strategy. Meanwhile, physicochemical properties of the resulting samples were investigated by series of techniques. Results showed that Ag/AgBr nano-particle exhibited intense light absorbance in the whole visible region, high photoinduced charge separation efficiency and visible light driven PC performance. Furthermore, the enhanced visible light PC mechanism was proposed and confirmed. Besides, the PC degradation pathways of acetaminophen were elucidated based on the UPLC-MS/MS measurement. Results indicated that five degradation intermediates were detected, consequently two tentative pathways for PC degradation of acetaminophen were proposed, for example hydroxylation addition to parent compound and CN cleavage of side chain from the acetaminophen attacked by photoinduced holes. This study provides a facile and feasible strategy to fabricate high-efficient visible light response of nano-materials which can be applied in the fields of waste water treatment.Download high-res image (113KB)Download full-size image

•CdS NCs/TiO2 NTs photoelectrodes were fabricated through anodization, followed by electrodeposition strategy.•The photoelectrochemical properties of CdS NCs/TiO2 NTs photoelectrode were studied.•An efficient and stable PEC system based on CdS NCs/TiO2 NTs photoanode and AC/PTFE cathode was constructed.•Contribution of each reactive species on PEC degradation of pollutants was distinguished.•The enhanced PEC mechanism of PEC system were proposed and confirmed.In this study, CdS NCs decorated TiO2 nano-tubes (CdS NCs/TiO2 NTs) photoelectrode was fabricated through anodization, followed by electrodeposition strategy. The resulting samples were characterized by SEM, XPS, UV–vis DRS and photoelectrochemical (PECH) measurements. It was found that the CdS NCs/TiO2 NTs photoelectrode exhibited intense visible light absorbance ranging from 400–700 nm and high transient photocurrent density of 9.62 mA cm−2. Furthermore, AC/PTFE cathode was prepared by rolling the AC and PTFE latex on a machine with the stainless steel as support. Subsequently, an effective and stable PEC system based on the as-fabricated CdS NCs/TiO2 NTs photoanode and AC/PTFE cathode was constructed for the degradation of RhB. Results showed that with the help of +2.0 V external potential, the PEC system exhibited superior PEC performance, in which 97.5% of RhB could be degraded. In addition, the generation rate of OH radicals and contribution of each reactive species to the PEC efficiency were also detected. Therefore, the efficient and stable PEC system based on CdS NCs/TiO2 NTs photoanode and AC/PTFE cathode could be a versatile candidate in pollutants elimination and water splitting.

In the present work, narrow band gap Ag2S nano-crystallites decorated TiO2 nanotubes arrays (Ag2S NCs/TiO2 NTAs) photoelectrode was successfully constructed through anodization, followed by successive ionic layer adsorption and reaction (SILAR) strategy. Subsequently, morphologies and chemical structures were investigated through scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). In addition, the optical and photoelectrochemical (PECH) properties were recorded through Ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), transient photocurrent density and Mott-Schottky measurements. Furthermore, the photocatalytic (PC) performance was evaluated through the yield of hydroxyl (·OH) radicals and degradation of methyl blue under visible light illumination. All results indicated that Ag2S NCs/TiO2 NTAs photoelectrode exhibited intense visible light absorbance, high transient photocurrent of 0.098 mA · cm−2 and charge carrier concentration of 1.58 × 1019 · cm−3, as well as effective PC performance of 83.6% for the degradation of methyl blue. Besides,  · OH radicals was the dominated responsible active species during the PC process. The enhanced visible light PC performance was mainly attributed to the intense visible light absorbance and high charge carrier separation efficiency.

In this study, we reported a facile strategy to fabricate N, Ti3+ codoped TiO2 nanotubes (N-Ti3+/TiO2 NTs) photoelectrode through one-step solution reduction process. The hydrazine hydrate treatment induced the simultaneous formation of Ti3+ species and N-doping in the lattice of TiO2 NTs. In addition, the N-Ti3+/TiO2 NTs photoelectrode exhibited intense visible light absorption ranging from 400 to 800 nm, high transient photoinduced current of 0.213 mA cm−2, charge carriers concentration of 0.92 × 1019 cm−3, generation of hydroxyl radicals and PEC efficiency of 100% for the degradation of diclofenac solution within 4 h visible light irradiation. The enhanced-visible-light PEC performance was mainly attributed to the enhancement of visible light absorbance, narrow band gap energy and high separation efficiency of photoinduced charge carriers. This study provides a facile strategy to construct intense visible light active catalyst, which could be applied in the fields of wastewater/air purification, solar energy conversion and water splitting.

•Pd-RGO/TiO2 NTs were prepared through two-step electrodeposition strategy.•The PEC properties of Pd-RGO/TiO2 NTs photoelectrode were investigated.•Contribution of active species to photodegradation of diclofenac was investigated.•The degradation kinetics of diclofenac over Pd-RGO/TiO2 NTs was studied.•The enhanced PC mechanism of Pd-RGO/TiO2 NTs was proposed and confirmed.In order to improve the separation efficiency of photogenerated charge carriers and photocatalytic (PC) performance of TiO2 nanotubes (TiO2 NTs) photoelectrode, Pd nanoparticles and reduced graphene oxide co-modified TiO2 NTs (Pd-RGO/TiO2 NTs) photoelectrode was fabricated through two-step electro-deposition in this study. Subsequently, physicochemical properties of the resulting samples were investigated through SEM, XRD, XPS and Raman techniques. Additionally, the generation of OH was detected by fluorescence spectra using terephthalic acid as the probing molecule. Furthermore, the photoelectrochemical properties of Pd-RGO/TiO2 NTs photoelectrode were studied through UV–vis DRS, photocurrent density and electrochemical impedance spectroscopy. As a result, Pd-RGO/TiO2 NTs photoelectrode exhibited a significantly enhanced photocurrent density of 0.111 mA cm−2 and charge carrier concentration of 1.43 × 1019 cm−3, as well as efficient PC performance of 58.4% for the degradation of diclofenac aqueous solution. Moreover, the enhanced-PC mechanism was proposed. The efficient visible PC performance of Pd-RGO/TiO2 NTs photoelectrode could mainly be attributed to the co-modification of Pd and RGO species, which could not only improve the light harvesting property, but also the effective separation of photogenerated charge carriers. Furthermore, the enhanced PC mechanism for degradation of diclofenac was proposed and confirmed. This study provides an effective strategy to fabricate TiO2 NTs-based photoelectrode which could be applied in the fields of organic pollutants elimination and wastewater treatment.

•PEC activities and kinetics for degradation of diclofenac were investigated.•Contribution of each active species to the degradation of diclofenac was studied.•PEC degradation pathways of diclofenac were elucidated in detail.•The stability of N, S–TiO2/TiO2 NTs photoelectrode was evaluated.Diclofenac is a common non-steroidal anti-inflammatory drug, which has been widely used in clinic that leads to the frequently detection in the freshwater bodies. In the present study, we explored the visible-light-driven photoelectrocatalytic (PEC) degradation of diclofenac solution by the as-fabricated N, S–TiO2/TiO2 NTs photoelectrode. Meanwhile, the PEC degradation performance and kinetics were also investigated. It was found that 73.3% of diclofenac could be degraded within 12 h visible light irradiation with the help of external potential (+0.4 V vs SCE). Additionally, the PEC processes followed the pseudo-first-order kinetics according to the Langmuir–Hinshelwood (L–H) model, in which the highest apparent rate constant of 0.101 h−1 could be achieved. Moreover, the further study of reactive species indicated that both H2O2 and OH radicals were responsible for the major degradation of diclofenac molecule. Besides, five degradation intermediates were elucidated by HPLC–MS/MS analysis. Based on these results, three tentative pathways for the PEC degradation of diclofenac solution were proposed, for example hydroxylation addition to parent pharmaceuticals, C–N cleavage of side chain from the diclofenac attacked by photogenerated holes and directly decarboxylation, subsequently dechlorination and oxidation processes. This study provides an effective strategy for the removal of pharmaceuticals from wastewater or freshwater bodies.Download high-res image (129KB)Download full-size image

•Pt NCs/TiO2 NTAs were fabricated by recycle pulse electrodeposition strategy.•Pt NCs/TiO2 NTAs photoelectrode exhibited high PECH and PEC performances.•Contribution of each active species to the degradation of aspirin was studied.•The PEC degradation pathways were proposed and confirmed.In this study, Pt NCs/TiO2 NTAs photoelectrode was fabricated through anodization process, followed by recycle pulse electrodeposition strategy. Subsequently, physicochemical properties of the resulting samples were studied systematically. Results indicated that Pt NCs/TiO2 NTAs photoelectrode exhibited intense light absorbance both in the UV and visible region, high transient photocurrent density of 0.089 mA cm−2 and open circuit potential of −0.275 V cm−2. In addition, 98.3% of aspirin could be eliminated within 4 h Xenon illumination with the help of +0.4 V potential. Furthermore, it can be concluded that two tentative pathways for PEC degradation of aspirin were proposed and confirmed.Download high-res image (90KB)Download full-size image

•Ag3PO4 was fabricated through ultrasound-precipitation strategy.•Ag3PO4 exhibited intense visible absorbance and high charge separation efficiency.•The optimized conditions for degradation of diclofenac were studied through CCD method.•The PC degradation pathways of diclofenac was proposed and confirmed.•The toxicity of the water samples at different illumination time was measured.In this study, high visible light response and charge separation efficiency of body-centered cubic Ag3PO4 sub-microcrystals were fabricated through ultrasound-precipitation process. Additionally, the parameters were optimized by photocatalytic (PC) removal degradation of diclofenac based on response surface methodology. Results indicated that the PC removal efficiency of diclofenac was significantly affected by Ag3PO4 content and pH value. Under the optimized conditions, 99.9% of diclofenac could be degraded within 16 min Xenon illumination. Furthermore, three PC removal degradation pathways of diclofenac were proposed, including OH-adduct to aromatic ring, direct oxidation by photoinduced holes and decarboxylation of side chain from the parent compound.Download high-res image (85KB)Download full-size image