Porous columnar nanostructured photoelectrodes may significantly affect the photoelectrochemical (PEC) water splitting efficiency. The glancing angle deposition (GLAD) technique is the most popular ...method to fabricate columnar nanostructured thin films. Here, we have fabricated vertically aligned porous 1D tungsten oxide nano-rod (1D WO3 NRs) thin films by DC magnetron sputtering method using glancing angle deposition with a constant rotation speed of 5 rpm. The depositions carried out at various deposition angles of α = 0°, 60°, 70°, 75°, 80°, and 85°. The deposited 1D WO3 NRs adopted a monoclinic structure oriented in the (002) crystalline plane perpendicular to the FTO substrate. Using systematic deposition conditions, the porous columnar 1D WO3 NRs were engineered to find the effect on the photoelectrochemical water splitting. Photocurrent density of the 1D WO3 NRs photoanodes was tested in near-neutral pH (0.5 M Na2SO4) electrolyte solutions. Under the optimum conditions, the 1D WO3NRs photoanode led to the premier photocurrent density of 1.04 mA/cm2 (1 V vs. Ag/AgCl) due to the optimum surface porosity in the 1D WO3 NRs. The individual layer of BiVO4 photoanode exhibited a photocurrent density of 1.24 mA/cm2 (1V vs. Ag/AgCl). Highest photocurrent density of 2.24 mA/cm2 with high photo-stability was observed in optimized heterostructure of 1D WO3 NRs/BiVO4 photoanode.
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•Vertically aligned columnar 1D WO3 nanorods were grown successfully by GLAD sputtering.•The surface porosity of 1D WO3 was changed by changing the glad angle.•The surface porosity of 1D WO3 nanorods have influences the photoelectrochemical properties.•BiVO4 decorated 1D WO3 nanorods exhibited good charge transfer properties and reduced charge recombination.•A stable photocurrent density was obtained 1D WO3/BiVO4 hetero structured photoanode.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Hematite (α‐Fe
2
O
3
) as a photoanode material for photoelectrochemical (PEC) water splitting suffers from the two problems of poor charge separation and slow water oxidation kinetics. The ...construction of p–n junction nanostructures by coupling of highly stable Co
3
O
4
in aqueous alkaline environment to Fe
2
O
3
nanorod arrays with delicate energy band positions may be a challenging strategy for efficient PEC water oxidation. It is demonstrated that the designed p‐Co
3
O
4
/n‐Fe
2
O
3
junction exhibits superior photocurrent density, fast water oxidation kinetics, and remarkable charge injection and bulk separation efficiency (η
inj
and η
sep
), attributing to the high catalytic behavior of Co
3
O
4
for the oxygen evolution reaction as well as the induced interfacial electric field that facilitates separation and transportation of charge carriers. In addition, a cocatalyst of cobalt phosphate (Co‐Pi) is introduced, which brings the PEC performance to a high level. The resultant Co‐Pi/Co
3
O
4
/Ti:Fe
2
O
3
photoanode shows a photocurrent density of 2.7 mA cm
−2
at 1.23 V
RHE
(V vs reversible hydrogen electrode), 125% higher than that of the Ti:Fe
2
O
3
photoanode. The optimized η
inj
and η
sep
of 91.6 and 23.0% at 1.23 V
RHE
are achieved on Co‐Pi/Co
3
O
4
/Ti:Fe
2
O
3
, respectively, corresponding to the 70 and 43% improvements compared with those of Ti:Fe
2
O
3
. Furthermore, Co‐Pi/Co
3
O
4
/Ti:Fe
2
O
3
shows a low onset potential of 0.64 V
RHE
and long‐time PEC stability.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A visible-light responsive dual photoelectrode photocatalytic fuel cell (PFC) which was consisted of n-type BiVO4/TiO2 nanotube (NT) photoanode and p-type Cu2O/TiO2 NT photocathode was successfully ...constructed for hazardous organics decomposition with simultaneous power recovery. The characterization proved the incorporation of BiVO4 and Cu2O not only increased the light harvesting efficiency of photoelectrodes but also improved their quantum yield, eventually exhibiting high photoelectrochemical performances. Significantly enhanced removal of tetracycline hydrochloride and electricity generation was obtained in the BiVO4/TiO2 NT-Cu2O/TiO2 NT PFC system. The rate constant of this dual photoelectrode PFC was 1.42 and 3.66 times as much as that of BiVO4/TiO2 NT-Pt PFC and Pt–Cu2O/TiO2 NT PFC, respectively, and the maximum power density was 1.68 and 103.8 folds as great as that of BiVO4/TiO2 NT-Pt PFC and Pt–Cu2O/TiO2 NT PFC. The enhancement was attributed to the large interior bias originated from the Fermi level difference between two electrodes, driving the photoelectrons of BiVO4/TiO2 NT to combine with the holes of Cu2O/TiO2 NT across external circuit and thus generating electricity. Meanwhile, organics were degraded by the anode holes, cathode electrons, and reactive oxygen species generated via chain reactions. The mechanism analysis confirmed the important roles of cathode electrons and anode holes, either acting as the oxidizing agent or the origination of hydroxyl radicals. Furthermore, the BiVO4/TiO2 NT-Cu2O/TiO2 NT PFC displayed good stability and reusability.
Aiming at enhancing the hazardous organics decomposition and power recovery, a visible-light responsive dual photoelectrode photocatalytic fuel cell (PFC) consisted of n-type BiVO4/TiO2nanotube (NT) photoanode and p-type Cu2O/TiO2NT photocathode was successfully constructed. The proposed PFC system provided a self-sustained and energy-saving methodology for simultaneous pollutants removal and electricity generation. Display omitted
•The BiVO4/TiO2 nanotube (NT) photoanode was developed.•The Cu2O/TiO2 NT photocathode was developed.•A visible-light-driven dual photoelectrode PFC was established.•The PFC operated utilizing the Fermi level difference between two photoelectrodes.•The PFC was efficient for electricity production and hazardous organics removal.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•A coral-like WO3/BiVO4 photoanode with exposed {110, 011} facets was fabricated.•The prepared photoanode showed enhanced separation and transfer of charge carriers.•A PEC-Cl system ...was constructed for wastewater remediation and H2 recovery.•RCS are the main active oxidation species for SXM removal in the PEC-Cl system.•The PEC-Cl system can efficiently remove SMX and reduce its toxicity.
Morphology and facet engineering have been proved efficient strategies to prepare high-performance photoelectrochemical (PEC) materials. WO3/BiVO4 heterojunction photoanodes with different morphologies were prepared by simply controlling the amount of electrodeposited charge. The coral-like WO3/BiVO4 photoanode with the orientation growth of {110} and {011} active facets of BiVO4 exhibited the optimal PEC performance due to significantly enhanced separation and transfer of photogenerated charge carriers, while the exposure of {−121} facets showed negative effects. 4.71 mA·cm−2 and 2.9 mA·cm−2 of photocurrent densities were obtained for sulfite and water oxidation, respectively, superior to most reported results. Subsequently, a photoelectrochemical-chlorine (PEC-Cl) system was constructed for antibiotic wastewater detoxification with hydrogen recovery. The analysis results indicated that the system can quickly and effectively remove sulfamethoxazole and reduce its toxicity concurrent with high hydrogen yield. The reactive chlorine species (RCS), especially Cl2·− and ClO·, dominated the sulfamethoxazole removal. Possible degradation pathways of sulfamethoxazole were also elucidated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Green and sustainable synthesis of NH3 is conducted by photoelectrochemistry.•A novel strategy of the photoanode synthesis of NH3 is suggested.•NiCe-layered double hydroxide and ...oxygen-vacancy Bi2O3 are used as photocatalysts.•Light utilization is improved by an Ag-mirror-film based light reflex strategy.•The NH3-synthesis mechanism is discussed by theoretical calculations.
Photoelectrocatalysis or photoelectrochemistry (PEC) strategies to synthesize NH3 by nitrogen reduction reaction (NRR) have attracted considerable attention in recent years, but the PEC-NRR synthesis of NH3 on photoanodes (vs commonly used photocathodes) is still a rather new topic worthy of in-depth study. Herein, the high-performance PEC-NRR synthesis of NH3 is achieved on an oxygen-vacancy Bi2O3 and then NiCe-layered double hydroxide modified fluorine-doped tin oxide photoanode biased at 0.4 V vs KCl-saturated calomel electrode, and the utilization of light source is improved by an Ag-mirror-film based light reflex. Under optimal conditions, the yield of NH3 is 16.9 mmol h−1 m−2, and it is increased to an apparent value of 27.8 mmol h−1 m−2 after counting the NRRs on both the photoanode and the Pt counter electrode, revealing that the photoanode strategy is promising for the green and sustainable synthesis of NH3 under ambient conditions. The NH3-synthesis mechanism is discussed after various characterizations and theoretical calculations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Bismuth Vanadate (BiVO4) photoanode has been popularly investigated for promising solar water oxidation, but its intrinsic performance has been greatly retarded by the direct pyrolysis method. Here ...we insight the key restriction of BiVO4 prepared by metal–organic decomposition (MOD) method. It is found that the evaporation of vanadium during the pyrolysis tends to cause a substantial phase impurity, and the unexpected few tetragonal phase inhibits the charge separation evidently. Consequently, suitably excessive vanadium precursor was adopted to eliminate the phase impurity, based on which the obtained intrinsic BiVO4 photoanode could exhibit photocurrent density of 4.2 mA cm−2 at 1.23 VRHE under AM 1.5 G irradiation, as comparable to the one fabricated by the currently popular two‐step electrodeposition method. Furthermore, the excellent performance can be maintained on the enlarged photoanode (25 cm2), demonstrating the advantage of MOD method in scalable preparation. Our work provides new insight and highlights the glorious future of MOD method for the design of scale‐up efficient BiVO4 photoanode.
The poor water oxidation performance of BiVO4 photoanode prepared by metal–organic decomposition was first unraveled to mainly result from the phase impurity caused by the relatively easy vanadium volatilization. Consequently, a BiVO4 photoanode free of tetragonal phase and decorated with NiFeOx cocatalyst was fabricated to exhibit a benchmark photocurrent density.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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•The CQDs/FeOOH/BiVO4 photoanode is prepared with dramatically enhanced PEC performance.•Synergetic catalysis of CQDs and FeOOH sharply improves the OER kinetics due to increased ...Ov.•The increased surface charge transfer kinetics dominates during the OER processes revealed by IMPS.•The CQDs/BiVO4 heterojunction efficiently suppresses the bulk charge recombination.•CQDs significantly boost the light harvesting both in the ultraviolet and visible regions.
Hydrogen generation by solar-driven water splitting is considered as a promising strategy to address energy crisisandenvironmental emission issues. Bismuth vanadate (BiVO4) is a highly promising photoanode material for photoelectrochemical (PEC) water splitting, but its severe bulk and surface charge recombination, sluggish oxygen evolution reaction (OER) kinetics and narrow visible light harvesting are still bottlenecks. Here, an excellent CQDs/FeOOH/BiVO4 photoanode was designed by co-modification of carbon quantum dots (CQDs) and ultrathin β-FeOOH layers (<10 nm) on BiVO4 to tackle the above issues. The CQDs/FeOOH/BiVO4 shows dramatically enhanced photocurrent, which is 10.7 and 2.98 times higher than BiVO4 and FeOOH/BiVO4 at 0.8 V vs. RHE (VRHE), with negatively shifted onset potential of 448 and 255 mV, respectively. The maximum incident photon-to-current conversion efficiency (IPCE) of CQDs/FeOOH/BiVO4 is 6.7 and 1.86 times higher than that of BiVO4 and FeOOH/BiVO4, respectively. Additionally, the surface hole injection efficiency (ηsurface) of CQDs/FeOOH/BiVO4 is 7.1 and 2.1 times higher than that of BiVO4 and FeOOH/BiVO4 at 0.8 VRHE, respectively. The results can be attributed to three effects: (i) Synergetic catalysis of CQDs and FeOOH sharply improves the OER kinetics due to the introduction of high-density oxygen vacancies (Ov); (ii) The CQDs/BiVO4 heterojunction efficiently suppresses the bulk charge recombination; (iii) CQDs significantly boost the light harvesting both in the ultraviolet and visible regions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•A facile CVD method was employed to introduce Mo doping on BiVO4 photoanode.•Mo doping will induce the reconstruction of BiVO4 surface, thereby forming a homojunction.•Oxygen ...vacancies will be generated by Mo doping, which is beneficial for OER reaction.•The CoPi/Graphene/Mo:BiVO4 photoanode exhibits excellent OER activity.•This work provide a promising strategy for designing high-performance BiVO4 photoelectrodes.
Fabrication junction and doping are the two major methods to improve the charge separation and transfer efficiency of BiVO4 (BVO) photoanode to boost its photoelectrochemical water splitting performance. Most of the reported methods require complicated fabrication steps, therefore increasing the usage of hazardous chemicals and cost as well. Herein, we report a BiVO4 homojunction with abundant oxygen vacancies fabricated by a surface crystal orientation reconstruction induced by one step Mo doping method. After Mo doping, a few nanometer BVO with crystal orientation of (121) is formed on BVO (110) surface with abundant oxygen vacancies on BVO photoanode. Mo doped BiVO4 photoanode (Mo:BVO) exhibits an obvious improvement of photocurrent (∼1.63 folds) compared with the pristine BVO. Using graphene as the hole extraction layer and CoPi as the cocatalysts, CoPi/Gr/Mo:BVO photoanode shows a high oxygen evolution reaction (OER) activity with the onset potential of 0.3 V vs. RHE and photocurrent of 4.36 mA cm−2 at 1.23 V vs. RHE under AM 1.5 G illumination. This work provides a promising strategy for the design of high-performance BiVO4 photoelectrodes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Understanding the origin of formation and active sites of oxygen evolution reaction (OER) cocatalysts is highly required for solar photoelectrochemical (PEC) devices that generate hydrogen ...efficiently from water. Herein, we employed a simple pH‐modulated method for in situ growth of FeNi oxyhydroxide ultrathin layers on BiVO4 photoanodes, resulting in one of the highest currently known PEC activities of 5.8 mA cm−2 (1.23 VRHE, AM 1.5 G) accompanied with an excellent stability. More importantly, both comparative experiments and density functional theory (DFT) studies clearly reveal that the selective formation of Bi−O−Fe interfacial bonds mainly contributes the enhanced OER activities, while the construction of V−O−Ni interfacial bonds effectively restrains the dissolution of V5+ ions and promotes the OER stability. Thereby, the synergy between iron and nickel of FeNi oxyhydroxides significantly improved the PEC water oxidation properties of BiVO4 photoanodes.
In situ growth of ultrathin FeNi oxyhydroxides on BiVO4 photoanodes by a simple pH‐modulated immersion significantly promoted the oxygen evolution activities and stability. This is attributed to the selectively interfacial bonding of Fe and Ni with surface Bi and V sites.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Metal protection of offshore equipment is very complicated owing to the complex marine environment. Photocathodic protection (PCP) is one of the popular research topics in marine metal protection. ...The protection efficiency of photoanode depends largely on the photoelectric properties of semiconductor materials, viz. the process of charge separation, charge migration, and light absorption. In this article, the enhancement strategies, photoelectrochemical properties, and electron transfer mechanisms of different composites for PCP were reviewed and highlighted. Some photoanodes with unusual and striking properties were emphasized. In addition, the outlooks and challenges of the application of PCP and the design of photoanodes materials are proposed.
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•The main photoanode enhancement strategies are reviewed.•Fabrication and enhancement strategies for semiconductor photoanode are emphasized.•Suggestion on novel photoanode material for marine environmental protection.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
