High Photoelectrochemical Performance Research Articles

Low Temperature Open-Air Plasma Deposition of SrTiO3 Films for Solar Energy Harvesting: Impact of Precursors on the Properties and Performances.

Strontium titanate (STO) is a well-known oxide used in a wide variety of applications due to its excellent stability and optoelectronic properties. However, its integration in photoelectrocatalytic devices is limited by the lack of fast and scalable methods to produce robust films at a low temperature and atmospheric pressure. Herein, we report an atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) approach for the synthesis of STO crystalline films and their applications for photoelectrochemical solar energy conversion. The film crystallinity, which plays a determinant role in the photoelectrochemical performance, was linked to the selected strontium precursor and injection method. Through thermal stability studies of the precursors [Sr(dpm), Sr(ipo), Sr(acac), and Ti(ipo)] and analysis of the solution droplet size, it was demonstrated that the closer thermal decomposition behavior and superior miscibility of the Sr(dpm) and Ti(ipo) precursors led to more homogeneous and crystalline films with the highest photoelectrochemical performance (16.5 μA cm-2 at 1.23 V vs RHE under 100 mW cm-2), which can be further improved by a factor of 3.4 using thermal annealing at 500 °C. Evidence of the impact of a strontium precursor on the properties of STO films is provided through thermogravimetric analysis, X-ray diffraction, energy-dispersive system, UV-vis, X-ray photoelectron spectroscopy, HIM-SIMS, and photoelectrochemical analysis.

Fabrication of Zn-MOF decorated BiVO4 photoanode for water splitting

Bismuth vanadate (BiVO4) is a promising photoanode material, which can be used for solar energy driven photoelectrochemical (PEC) water splitting to produce hydrogen at room-temperature. However, the PEC performance of BiVO4 is still seriously hindered due to low carrier transmission efficiency and slow water oxidation kinetics. Here, Zn-MOF with large surface area and abundant exposed active sites was decorated on BiVO4 photoanode, exhibiting boosted PEC activity. The optimal photocurrent of BiVO4/Zn-MOF reaches 3.1 times of that of bare BiVO4. The charge separation efficiency of BiVO4/Zn-MOF increased to 50.46%, about 2.16 times of BiVO4. The charge injection efficiency of BiVO4/Zn-MOF rises from 14.0% to 76.8%. The improved carrier transport efficiency and reaction kinetics suggest that Zn-MOF material plays crucial role in the construction of high performance PEC water splitting system.

Role of G-C3n4 in Fabrication of Bivo4/Wo3 Z-Scheme Heterojunction for High Photoelectrochemical Performances with Enhanced Light Harvesting

Role of G-C3n4 in Fabrication of Bivo4/Wo3 Z-Scheme Heterojunction for High Photoelectrochemical Performances with Enhanced Light Harvesting

Hierarchically Interconnected G-C3n4/Bivo4/Zno Array Via Spin Coating for High Photoelectrochemical Performance

Hierarchically Interconnected G-C3n4/Bivo4/Zno Array Via Spin Coating for High Photoelectrochemical Performance

Stable and Efficient Photoinduced Charge Transfer of MnFe2O4/Polyaniline Photoelectrode in Highly Acidic Solution

Tailoring conductive polymers with inorganic photocatalysts, which provide photoinduced electron-hole generation, have significantly enhanced composites leading to excellent photoelectrodes. In this work, MnFe2O4 nanoparticles prepared by a hydrothermal method were combined with polyaniline to prepare mixed (hybrid) slurries, which were cast onto flexible FTO to prepare photoelectrodes. The resulting photoelectrodes were characterized by XRD, FESEM, HRTEM and UV-VIS. The photoelectrochemical performance was investigated by linear sweep voltammetry and chronoamperometry. The photocurrent achieved by MnFe2O4/Polyaniline was 400 μA/cm2 at 0.8 V vs. Ag/AgCl in Na2SO4 (pH = 2) at 100 mW/cm2, while polyaniline alone achieved only 25 μA/cm2 under the same conditions. The best MnFe2O4/Polyaniline displayed an incident photon-to-current conversion efficiency (IPCE) and applied bias photon-to-current efficiency (ABPE) of 60% at 405 nm wavelength, and 0.17% at 0.8 V vs. Ag/AgCl, respectively. High and stable photoelectrochemical performance was achieved for more than 900 s in an acidic environment.

Novel K-doped TiO2 nanotube arrays with superhydrophilic surface and high photoelectrochemical cathodic protection

K-doped TiO2 nanotube arrays with superhydrophilicity and high photoelectrochemical cathodic protection performance were prepared via simple anodization and hydrothermal method. The high photoelectroactivity and high photoelectrochemical cathodic protection performance were proven on the basis of photoinduced I–V curves, Mott–Schottky plots, and open circuit potential of coupling electrode. The mechanism of high photoelectrochemical cathodic protection performance was verified on the basis of ultraviolet–visible spectroscopy diffused reflectance spectra, ultraviolet photoelectron spectroscopy, and contact angle.

Bifunctional photoelectrochemical sensor based on Bi/Bi2S3/BiVO4 for detecting hexavalent chromium and hydrogen peroxide

In this study, a bifunctional photoelectrochemical (PEC) sensor based on Bi/Bi2S3/BiVO4 (Bi-BSV) is prepared by one-step hydrothermal method. Firstly, the results from experiments show that the PEC performances of Bi2S3/BiVO4-X (BSV-X, X = m(Bi2S3)/m(Bi2S3 + BiVO4)) are higher than those of Bi2S3 and BiVO4, and BSV-15% has the highest PEC performance. To further improve the PEC properties of BSV-15%, metal-Bi was introduced to the synthesis of Y-Bi-BSV-15% (Y represents the amount of glucose added). Moreover, UV–visible diffuse reflectance spectrum (UV–vis DRS) and photoluminescence (PL) demonstrate that 0.3-Bi-BSV-15% has the widest visible light absorption range and strongest photogenerated carriers separation capability among all composites. Based on the above results, the PEC sensor based on the 0.3-Bi-BSV-15% for detecting hexavalent chromium (Cr (VI)) and hydrogen peroxide (H2O2) is built. The results exhibit that 0.3-Bi-BSV-15% has a wider detection range of 2–230 µM and a lower detection limit of 0.094 µM for Cr (VI) detection. While for H2O2 detection, the detection range and detection limit are 1–130,000 µM and 0.089 µM, respectively. Therefore, 0.3-Bi-BSV-15% has potential application in Cr (VI) and H2O2 detection.

Dye sensitized Ti3C2 MXene-based highly sensitive homogeneous photoelectrochemical sensing of phosphate through decomposition of methylene blue-encapsulated zeolitic imidazolate framework-90

The previously reported homogeneous photoelectrochemical (PEC) sensor often suffers from the shortcomings of complicated dye-labeling procedure, poor photocurrent intensity, and weak stability. Exploiting novel homogeneous PEC sensors to circumvent above limitations is badly instant but faces a major challenge. This study presents a Ti3C2 MXene-based label-free homogeneous PEC sensor for highly sensitive analysis of phosphorus used methylene blue (MB) sensitized MXene@ITO photoelectrodes and functional zeolitic imidazolate framework-90 (ZIF-90). The MB sensitized MXene@ITO photoelectrodes exhibited excellent stability and elevation of photocurrent intensity. The MB was performed to encapsulate into ZIF-90 to form MB@ZIF-90 with one-step strategy. The prepared MB@ZIF-90 could be decomposed by target phosphorus due to the stronger coordination between phosphorus and Zn2+. As compared to the case where phosphorus was absent, a lot of MB was released and diffused to the MXene@ITO photoelectrode surface, and markedly increased PEC current was gained. Therefore, via these targets induced MB release mode and MB sensitized Ti3C2 MXene@ITO photoelectrodes, a high-performance homogeneous PEC phosphorus assay is realized, with a detection limit down to 0.21 μM. The phosphorus analysis with recovery ranged from 98.3% to 103.4% in environmental and biological samples, demonstrating the potential applicability of this PEC sensor.

Facile in situ fabrication of rGO/MoS2 heterostructure decorated with gold nanoparticles with enhanced photoelectrochemical performance

Two-dimensional materials offer a promising visible light-driven photoelectrochemical (PEC) application thanks to their high electrical conductivity and tunable bandgap. However, the high recombination rate of photogenerated carriers significantly limits their photoelectrochemical efficiency. Here, a reduced graphene oxide/molybdenum disulfide/gold nanoparticles (rGO/MoS2/Au NPs) heterostructure is introduced based on a simple and high-throughput method to efficiently convert light into electricity. For this purpose, MoS2 dispersion is cast on GO few layers followed by sputtering 5 nm thin film of gold. With a thermal-assisted method not only GO is reduced to rGO but also Au is converted into Au NPs. The introduced heterostructure is thoroughly studied by SEM, TEM, Raman, UV–Visible, and AFM analyses. The rGO/MoS2/Au NPs heterostructure demonstrates about 240% improvement in photocurrent density compared with GO/MoS2 hybrid which is due to the efficient transfer of electrons to Au NPs and a significant reduction in the recombination rate of photogenerated carriers. Straightforward fabrication of such a high-performance PEC heterostructure is very promising for photoelectrochemical and energy generation applications. Finally, using numerical simulations, the mechanism of the photogenerated carriers is well elucidated in the suggested heterostructure, which shows complete agreement with the experimental results.

Doping Mo on Tungsten Oxide Thin Film and Photoelectrochemical Measurement

Tungsten oxide (WO₃) is semiconductor material which can be used for various applications. Especially, one-dimensional (1-D) nanostructured WO₃ shows the high photoelectrochemical (PEC) performance due to high surface area and short transport route of electron-hole pair. The flame vapor deposition (FVD) process is an efficient and economical method for preparation of the 1-D nanos-tructured WO₃ thin film. Molybdenum doping is a well-known method to improve the PEC performance of WO₃ by reducing band gap and increasing electrical property. In this study, we prepared the 1-D WO₃ nanostructures doped with Mo by FVD single step process. We confirmed that Mo was successfully doped on WO₃ without changing significantly the original nanostructure, crystal structure and chemical bonding state of WO₃ thin film. As a result of PEC measurement, the pho-tocurrent densities of WO₃ thin film with Mo doping were higher by about 1.4 to 2 times (for applied voltage above 0.7 V vs. SCE) than those without Mo doping.

Self-powered visible photodetector with fast-response speed and high stability based on vertical (In,Ga)N nanowires

Energy-saving photodetector (PD) with fast response speed is a key component of the next-generation photonic systems. In this work, self-powered photoelectrochemical (PEC) PD based on vertical (In,Ga)N nanowires (NWs) has been proposed and demonstrated successfully. With deionized water solution, the (In,Ga)N NWs are stable and the PEC PD is eco-friendly. The PEC PD has a good stability in terms of good on/off switching behaviors after continuously working for a few hours. The PD exhibits a high sensitivity under very low light illumination intensity of 6.4 μW/cm2. A fast rise/fall time of ∼54/55 ms with good symmetry can also be achieved. Moreover, the NW core-shell structure is proposed to provide an additional way for electron-hole carrier transport, which could play a key role in accelerating the response speed. This work paves a way to develop high-performance PEC PDs for the wide applications in wireless visible photodetection and communication.

Heterostructure between WO3 and metal organic framework-derived BiVO4 nanoleaves for enhanced photoelectrochemical performances

The BiVO4/WO3 heterojunction is one of the most promising photoanode materials for water splitting. Designing BiVO4/WO3 nanostructures that can provide more active sites and suppress charge recombination is essential for improving the photoelectrochemical (PEC) performance. In this study, BiVO4 nanoleaves (NLs) with a high surface area were synthesized on either the surface of WO3 thin films (TF) or on nanorods (NRs) via metal organic framework (MOF)-templated synthesis. The growth of the CAU-17 template and its subsequent reaction with vanadium sources at high temperatures enabled the preparation of BiVO4 NLs with highly uniform compositions. At 1.23 V vs. RHE, the photocurrent densities of BiVO4-NLs/WO3-TF and BiVO4-NLs/WO3-NRs were 1.45 and 2.83 mA/cm2, respectively, where both values are significantly higher than achieved with the bare WO3 counterparts. The high PEC performance is due to the enhanced absorption of visible light by the BiVO4 NLs and efficient charge separation at the type II heterojunction between BiVO4 and WO3. Moreover, the PEC performance of BiVO4-NLs/WO3-NRs demonstrated that the formation of more heterointerfaces via the morphological design of the WO3 bottom layer can further enhance the photoanode efficiency. The MOF-derived synthesis of BiVO4 NLs provides a novel strategy for designing uniform and highly efficient heterostructure photoanodes.

Fabrication of multilayer 1D TiO2/CdS/ZnS with high photoelectrochemical performance and enhanced stability

Nano TiO2 is a basic photoanode material in the application of new type solar cell for its appropriate bandgap and photoemission. However, traditionally TiO2-based photoanode films are limited in weak photoresponse and effortless recombination. Herein, we increase light absorption range through combined the uniform CdS quantum dots (QDs) by successive ionic layer adsorption reaction (SILAR) method and decrease the recombination of photo-generated electrons/holes through ZnS passivation layer overlaying on TiO2/CdS. Photocurrent response (i-t), photocurrent density-voltage (J-V) curves of TiO2/CdS/ZnS demonstrated the photovoltaic conversion efficiency (η) has been reaching 3.43%, which has 230% and 33% improvement than pure TiO2 and TiO2/CdS.

A bridging coordination of urea tailoring metal hydroxides oxygen evolution catalysts promotes stable solar water splitting

Stability is one of essential factors for evaluating the photoelectrochemical (PEC) water splitting performance on photocorroded semiconductors for practical applications. Cocatalyst decoration can only maintain the stability for several hours, and organic/inorganic hybrid photoelectrodes (e.g. polymer coated photoelectrodes) also has a limited durability. Therefore, it is challenging to develop a facile but effective approach for stabilizing the photoelectrodes. In this work, we induced a handful of cheap urea into the Ni,Fe-based hydroxides as robust and conformal OECs layers, deposited on the BiVO4 photoanodes by an one-step impregnation process. Urea, an assisted nitrogen/carbon source, played an active role on the uniform growth of ultrathin OEC layer, replacing the complex organic cocatalyst. The thickness of urea induced Ni,Fe-based OEC could be modified by tuning the amount of urea, thereby improving the carrier dynamics and protecting photoelectrodes from photocorrosion. The presence of urea facilitates to deposit a homogeneous cocatalyst layer with higher electron transfer than the absence of urea, resulting in a high electrocatalytic OER and PEC performance. The optimized urea-NiFeOOH/BiVO4 photoanode showed a photocurrent density of 4.8 mA cm−2 at 1.23 VRHE with impressive stability over 40 h at a potential of 0.8 VRHE, which is one of the best PEC stabilities using NiFe-based OECs on BiVO4. Benefiting from the strong coordination bond between the metal ions and urea, the C and N elements remained stable in the OEC layer before and after PEC test. This work presents a potential application using cheap, non-precious metal based electrocatalysts to overcome the bottle-necks limiting a long-term stability of PEC water splitting.

Improving the photoelectrochemical performance of spin-coated WO3/BiVO4/ZnO photoanodes by maximizing charge transfer using an optimized ZnO decoration layer

The photoelectrochemical (PEC) method has potential for harvesting solar energy to eventually resolve the fossil fuel crisis owing to its green and renewable characteristics and inherently low conversion efficiency. Herein, we introduce a controlled ZnO decoration layer on a WO3/BiVO4 type II heterojunction array using a facile spin-coating method to enhance the PEC performance of photoelectrodes. The ZnO decoration layer plays a crucial role in attaining superior charge transfer, reduced charge recombination, and stable photoactivity in the composite WO3/BiVO4/ZnO systems. An optimally decorated ZnO layer with oxygen vacancies in the WO3/BiVO4/ZnO photoanode allows extended light absorbance in the UV and visible wavelength regions with a narrow band gap and passivates the underlying WO3/BiVO4 type II heterojunction surfaces by covering the defect sites. Thus, the optimized WO3/BiVO4/ZnO-3 photoanode exhibits the highest photocurrent density (190 μA cm−2 at 1.23 VRHE) with the lowest onset potential (0.41 VRHE), reproducible photo-reaction under chopped light, the smallest charge transfer resistance in the Nyquist plot (1755 Ω), the highest quantum efficiencies for ABPE, IPCE, and APCE (0.036% at 0.92 VRHE, 6% at 380 nm at 1.23 VRHE and 11% at 380 nm, respectively), the highest reliability (30% decay after 1500 s), and high charge injection (63%) and charge separation (7.3%) efficiencies. These findings demonstrate that the component optimization in WO3/BiVO4/ZnO-x composite photoelectrodes is crucial in achieving high PEC performance by improving charge separation and reducing charge recombination.

Influence of Applied Potential on Electrodeposited ZnSe/ZnO Nanostructured Films for Photoelectrochemical Cell

Zinc oxide (ZnO) nanorods is widely investigated due to its high photoelectrochemical conversion performance. Further enhancement may be afforded by introducing a metal chalcogenide sensitization layer such as zinc selenide (ZnSe). In this study, ZnO nanorods were electrodeposited with ZnSe at potential range from -0.5 V to -0.9 V vs Ag/AgCl reference electrode. Structural, morphological and optical properties of ZnSe electrodeposited were investigated as a function applied potential by using X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), and ultraviolet-visible spectroscopy (UV-Vis). ZnSe electrodeposited for 15 minutes at -0.7 V showed crystallite size of 20.13 nm with the lowest band gap energy of 2.97 eV. The existence of ZnSe particles with the size of 41.8 nm were proven by FESEM images, after ZnSe particles were electrodeposited onto ZnO nanorods that have an average diameter of 62.6 nm and length of 1.6 µm. The photocurrent density generated by samples were measured in a three-electrodes cell incorporated with halogen lamp. The photocurrent generated increased between -0.5 V to -0.7 V before dropped at higher applied potential due to hydrogen evolution process which affected the thin film quality, ultimately affecting photoconversion performance. The highest photocurrent density of 0.2621 mAcm-2 was recorded for samples prepared at -0.7 V vs Ag/AgCl.

High photoelectrochemical performance of a p‐type reduced grapheneoxide‐copperoxide/Cu foil (rGO‐CuO/Cu) photoelectrode prepared by a one‐pot hydrothermal method

High photoelectrochemical performance of a p‐type reduced graphene<scp>oxide‐copper</scp>oxide/Cu foil (<scp>rGO‐CuO</scp>/Cu) photoelectrode prepared by a one‐pot hydrothermal method

Mo-doped ZnV2O6/reduced graphene oxide photoanodes for solar hydrogen production

We report the fabrication and characterization of molybdenum (Mo)-doped ZnV2O6/reduced graphene oxide (rGO) composite and its use as photoanode for photoelectrochemical (PEC) hydrogen production. Compared to pure ZnV2O6, Mo ions act as electron donor in the ZnV2O6:Mo lattice increasing charge carrier concentration and subsequently mobility in the bulk by the polaron transport. We measured the hole transfer efficiency for the pure and Mo-doped ZnV2O6 electrodes and revealing a substantial increase from 16 to 25%. The mechanism of enhanced photoactivity of Mo-doped ZnV2O6 was studied by density functional theory calculations. Moreover, electrochemical impedance spectroscopy measurements show that graphene modification improves carrier separation and transfer across the electrode/electrolyte interface. Therefore, the combination of the two strategies triggers a synergistic enhancement in PEC performance in terms of incident photon-to-current efficiency, which is 17% at 370 nm, being 4.5- and 3.6-times greater than those of pristine ZnV2O6 and ZnV2O6:Mo photoanodes, respectively. With photocurrent onset potentials of 0.6 V and photocurrent densities of 2.07 mA/cm2 at 1.23 V vs. RHE, ZnV2O6:Mo/rGO photoanodes are of interest for the design of high performance PEC visible-light-induced water-splitting devices.

Ultra-sensitive photoelectrochemical aptamer biosensor for detecting E. coli O157:H7 based on nonmetallic plasmonic two-dimensional hydrated defective tungsten oxide nanosheets coupling with nitrogen-doped graphene quantum dots (dWO3•H2O@N-GQDs)

Light absorption and interfacial engineering of photoactive materials play vital roles in photoexcited electron generation and electron transport, and ultimately boost the performance of photoelectrochemical (PEC) biosensing. In this work, a novel high-performance photoelectrochemical (PEC) biosensing platform was fabricated based on nonmetallic plasmonic tungsten oxide hydrate nanosheets (WO3•H2O) coupling with nitrogen doped graphene quantum dots (N-GQDs) by a facile one-step hydrothermal approach. The localized surface plasmon resonance (LSPR) properties were achieved by oxygen vacancy engineered WO3·H2O (dWO3•H2O), which could greatly extend the light absorption from visible light to near-infrared light. Moreover, by coupling with N-GQDs, the as-fabricated heterojunction (dWO3•H2O@N-GQD) provided a much enhanced photoelectric response due to the efficient charge transfer. By conjugation with E.coli O157:H7 aptamer, a novel PEC aptasensor based on dWO3•H2O@N-GQD heterojunction was fabricated with a high sensitivity for detection of E.coli O157:H7. The limit of detection (LOD) of this PEC aptasensor is 0.05 CFU/mL with a linear detection range from 0.1 to 104 CFU/mL. Moreover, high reproducibility and good accuracy could also be achieved for analysis in milk samples. This work could provide a promising platform for the development of PEC bioanalysis and offer an insight into the non-metallic plasmonic materials based heterojunctions for high-performances PEC biosensing.

Engineering Nanostructure-Interface of Photoanode Materials Toward Photoelectrochemical Water Oxidation.

Photoelectrochemical (PEC) water oxidation based on semiconductor materials plays an important role in the production of clean fuel and value-added chemicals. Nanostructure-interface engineering has proven to be an effective way to construct highly efficient PEC water oxidation photoanodes with good light capture, carrier transport, and water oxidation kinetics. However, from theoretical and application perspectives, the relationship between the nanostructure and interface of photoanode materials and their PEC performance remains unclear. In this review, the PEC water oxidation reaction mechanism and evaluation criteria are briefly presented. The theoretical basis and research status of the nanostructure-interface engineering on constructing high-performance PEC water oxidation photoanodes are summarized and discussed. Finally, the current challenges and the future opportunities of nanostructure-interface engineering for the PEC reactions are pointed out.