Enhanced Photoelectrochemical Activity Research Articles

A novel photoelectrochemical aptasensor based on 3D flower-like g-C3N4/BiOI p-n heterojunction for the sensitive detection of kanamycin

BackgroundKanamycin (KAN) residues in animal-derived foods continuously enter the human body, which will pose serious threats to human health such as hearing loss, nephrotoxicity and other complications. Therefore, to sensitively detect KAN residues by a reliable technology is extremely urgent in food quality and safety. Compared with traditional methods being limited by cost and complexity, photoelectrochemical (PEC) biosensors benefit from some merits such as rapid response, excellent sensitivity and good stability. In this study, the construction of a highly efficient PEC platform to realize KAN residues detection is discussed. ResultsHerein, a novel p-n heterojunction consisting of flower-like BiOI microspheres and graphite carbon nitride (g-C3N4) nanoflakes was developed to establish a PEC aptasensor for KAN detection at 0 V. The prepared g-C3N4/BiOI heterostructure showed not only significantly enhanced PEC activity due to the larger specific surface area but also greatly increased charge separation efficiency owing to the strong internal electric field. Meanwhile, using g-C3N4/BiOI as a highly efficient photoactive material for binding amine-functionalized aptamers to capture KAN, the photocurrent signals showed a ‘turn off’ mode to achieve the sensitive detection of KAN. The proposed PEC aptasensor exhibited linear response for KAN from 5 × 10−9 to 3 × 10−7 mol L−1 with a low detection limit of 1.31 × 10−9 mol L−1, and satisfactory recoveries (97.44–107.38 %) were obtained in real food samples analysis. SignificanceThis work presented a novel p-n heterojunction-based PEC aptasensor with strong selectivity and stability, rendering it allowed to detect KAN in animal-derived foods including milk, honey and pork. Additionally, the detection range satisfied the MRLs for KAN specified by the national standards, demonstrating the potential application for food analysis. The study provides a new insight into the development of efficient and practical biosensors for antibiotic residues detection.

Oxygen-doped ZnIn2S4 as a highly active and etchable photoactive material for chlorpyrifos detection

The development of a high-performance photoactive material and an effective and efficient analysis strategy are important for photoelectrochemical (PEC) analysis. We report here the enhanced PEC activity and etchable property of oxygen-doped ZnIn2S4 (O-ZnIn2S4) and its application for PEC detection of organophosphorus pesticides (OPs). O-ZnIn2S4 prepared by thermally treating ZnIn2S4 in air atmosphere can show much higher PEC activity than pristine ZnIn2S4, because oxygen doping can decrease the band gap and thereby increase the visible-light absorption. It is found that O-ZnIn2S4 can be etched by hydrogen peroxide, so O-ZnIn2S4 can be used for PEC analysis based on the etching strategy. Enzymatic reactions catalyzed by acetylcholinesterase and choline oxidase can produce hydrogen peroxide to etch the O-ZnIn2S4 modified on photoelectrode, so a “signal-off” state is achieved. OPs can inhibit the activity of acetylcholinesterase, and the etching of O-ZnIn2S4 is weakened, enabling “signal-on” PEC detection of OPs. Chlorpyrifos is selected as a model for PEC detection of OPs. The detection limit for chlorpyrifos detection is 2 × 10−4 mg L−1 with a linear range from 0.001 to 50 mg L−1. The present study not only develops a high-performance photoactive material for PEC analysis but also provides an efficient PEC sensing strategy based on ZnIn2S4 etching.

Enhanced Photoelectrochemical Activity Realized from WS2 Thin Films Prepared by RF‐Magnetron Sputtering for Water Splitting

AbstractWe report the synthesis of tungsten sulfide (WS2) films using RF‐magnetron sputtering at different RF powers. X‐ray diffraction (XRD) data confirm the hexagonal crystal structure of WS2 with an average crystallite size of ∼44.54 Å. With increased RF power, the preferred orientation of WS2 crystallites shifts from (002) to (100). Linear sweep voltammetry (LSV) was used to assess the Photoelectrochemical (PEC) activity of WS2 films. The film deposited at 150 W demonstrated the highest photocurrent density of 5.44 mA/cm2. The 150 W film also showed a lower Tafel slope of ∼0.374 V/decade, indicating superior PEC activity. Mott Schottky's (MS) analysis revealed a notable shift in the flat band potential towards the negative side, suggesting a shifting of the Fermi level towards the conduction band. WS2 film grown at 150 W demonstrated a majority charge carrier density of 6.2×1021 cm−3 and a depletion layer width of 1.54 nm. The observed low charge transfer resistance of 155 Ω contributed to the enhanced PEC activity with a relaxation time constant of 37 ms. These properties suggest that WS2 can be suitable for PEC water splitting.

Encapsulation of few-layered MoS2 on electrochemical-treated BiVO4 nanoarray photoanode: Simultaneously improved charge separation and hole extraction towards efficient photoelectrochemical water splitting

Bismuth vanadate (BiVO4) photoanode shows great potential for photoelectrochemical (PEC) water splitting but still suffers from the sluggish surface reaction kinetic and high charge loss. Further strengthening the intrinsic charge transport for the improvement of solar-to-hydrogen conversion becomes the top priority. Herein, an innovative highly-oriented E-BiVO4/MoS2 heterojunction photoanode is rationally designed and fabricated via directly encapsulating few-layered MoS2 nanosheets on electrochemical-treated BiVO4 (E-BiVO4) nanopyramid arrays. Systematic studies reveal that the electrochemical reduction process can create oxygen vacancies on BiVO4 lattice, thereby increasing the overall carrier concentration, and boosting the bulk and surface charge separation efficiencies. Meanwhile, the introduction of MoS2 as a heterojunction helps build the unidirectional charge transfer channels for further facilitated surface hole extraction and oxidation kinetics, synergistically devoting to the significantly enhanced PEC activity and photostability. As a result, the optimized E-BiVO4/MoS2 photoanode exhibits the highest photocurrent density of 2.11 mA/cm2 at 1.23VRHE and incident photon-to-electron conversion efficiency (IPCE) of 40.6 %, which are approximately 4.6 and 4.9 times higher than the pristine BiVO4. The present work demonstrates a feasible collaborative strategy to develop photoanodes with simultaneously improved charge separation and hole transport for efficient PEC water splitting application.

MoS2 modified NiFe LDH hierarchical structure as efficient photoanode towards photoelectrochemical water splitting

Designing effective photo electrode for photo-electrochemical (PEC) water splitting is highly demanded yet challengeable because of the limited sunlight utilization and retarded redox reaction kinetics. This work introduces a feasible one-pot hydrothermal strategy of fabricating MoS2/NiFe LDH p-n heterojunctions on conductive porous nickel foam as an efficient photoanode for PEC water splitting. A great enhancement for PEC water oxidation is achieved because of the improved sunlight absorption and the increased photo-excited charge separation. The optimal 10% MoS2/Ni0.9Fe0.1 LDH/nickel foam photoanode demonstrates 3.8 times enhanced PEC activity than the Ni0.9Fe0.1 LDH/NF counterpart and a low Tafel plot of 54 mV dec−1. The bandgap modulation and the Z-scheme charge transfer dynamics due to the formation of MoS2/NiFe LDH p-n heterostructure, along with the high conductivity of porous nickel foam account for the increased photo-current conversion efficiency and the boosted charge transfer.

Enhanced photoelectrochemical water splitting in ternary layered chalcogenide ZnIn2S4 coupled with MWCNT

Layered hexagonal zinc indium sulfide coupled with multiwalled carbon nanotubes (MWCNT/H-ZnIn2S4) nanocomposites were prepared via using the hydrothermal method and investigated its photoelectrochemical (PEC) water-splitting properties. A series of MWCNT/H-ZnIn2S4 nanocomposites with different concentrations of MWCNT have been synthesized. The effects of the addition of different concentrations of MWCNT on the PEC performance of H-ZnIn2S4 material are studied. The outcomes showed that the maximum value of photocurrent density is obtained for 20 wt% MWCNT/H-ZnIn2S4, which is ∼3.8 times higher as compared to the H-ZnIn2S4 photoanode under visible light illumination. The enhancement in the current density is because of the electron-accepting behavior of MWCNT that helps in the effective separation and transfer of charges at the interface. The ability of MWCNT to accept and transport electrons offers a better path to regulate the movement of photogenerated charge carriers, extending the lifetime of the photogenerated charges produced in the semiconductors. A plausible mechanism for observed enhanced PEC activity of MWCNT/H-ZnIn2S4 nanocomposites is provided, which is supported by impedance spectroscopy and Mott-Schottky results.

Enhanced photoactivity towards bismuth vanadate water splitting through tantalum doping: An experimental and density functional theory study

The activation of hole trap states in bismuth vanadate (BiVO4) is considered an effective strategy to enhance the photoelectrochemical (PEC) water-splitting activity. Herein, we propose a theoretical and experimental study of tantalum (Ta) doping to BiVO4 leading to the introduction of hole trap states for the enhanced PEC activity. The doping of Ta is found to alter the structural and chemical surroundings via displacement of vanadium (V) atoms that cause distortions in the lattice via the formation of hole trap states. A significant enhancement of photocurrent to ∼4.2 mA cm−2 was recorded attributing to the effective charge separation of efficiency of ∼96.7 %. Furthermore, the doping of Ta in the BiVO4 lattice offers improved charge transport in bulk and decreased charge transfer resistance at the electrolyte interface. The Ta-doped BiVO4 displays the effective production of hydrogen (H2) and oxygen (O2) under AM 1.5 G illumination with a faradaic efficiency of 90 %. Moreover, the density functional theory (DFT) study confirms the decrease in optical band gap and the activation of hole trap states below the conduction band (CB) with a contribution of Ta towards both valence and CB that increases the charge separation and majority charge carrier density, respectively. The findings of this work propose that the displacement of V sites with Ta atoms in BiVO4 photoanodes is an efficient approach for enhanced PEC activity.

Enhancement of the Solar Water Splitting Efficiency Mediated by Surface Segregation in Ti-Doped Hematite Nanorods.

Band engineering is employed thoroughly and targets technologically scalable photoanodes for solar water splitting applications. Complex and costly recipes are necessary, often for average performances. Here, we report simple photoanode growth and thermal annealing with effective band engineering results. By comparing Ti-doped hematite photoanodes annealed under nitrogen to photoanodes annealed in air, we found a strongly enhanced photocurrent of more than 200% in the first case. Using electrochemical impedance spectroscopy and synchrotron X-ray spectromicroscopy, we demonstrate that oxidized surface states and increased density of charge carriers are responsible for the enhanced photoelectrochemical (PEC) activity. Surface states are found to be related to the formation of pseudo-brookite clusters by surface Ti segregation. Spectro-ptychography is used for the first time at the Ti L3 absorption edge to isolate Ti chemical coordination arising from pseudo-brookite cluster contribution. Correlated with electron microscopy investigation and density functional theory calculations, the synchrotron spectromicroscopy data unambiguously prove the origin of enhanced PEC activity of N2-annealed Ti-doped hematite nanorods. Finally, we present here a handy and cheap surface engineering method beyond the known oxygen vacancy doping, allowing a net gain in the PEC activity for the hematite-based photoanodes.

Ti-doped Fe2O3 photoanodes on three-dimensional titanium microfiber felt substrate for photoelectrochemical oxygen evolution reaction

The macroporous structure of conductive substrates with large surface areas is crucial for fabricating semiconductor electrodes that offer better photoelectrochemical (PEC) performance in the water-splitting reaction. In this study, three-dimensional (3D) titanium microfiber felt (Ti felt) was used as a conductive substrate to prepare a Ti-doped Fe2O3 photoanode via a hydrothermal method with a two-step annealing treatment in air and argon atmospheres. Compared to conventional two-dimensional (2D) substrates, such as fluorine-doped tin oxide (FTO)-coated glass and Ti sheets, the loading amount of Fe2O3 on Ti felt was 2–5 times higher for a similar substrate geometric area. The thickness of Fe2O3 on the Ti felt (∼0.6 µm) was less than that on the 2D substrates. Ti-doped Fe2O3 on Ti felt (Ti-felt/Ti-Fe2O3) exhibits a higher photocurrent density than FTO/Ti-Fe2O3 and Ti-sheet/Ti-Fe2O3. Mott–Schottky analysis shows that the donor density of Ti-felt/Ti-Fe2O3 (8.58 × 1021 cm−3) was more than 10 times higher than that of FTO/Ti-Fe2O3 and Ti-sheet/Ti-Fe2O3. Analyses of the incident photon-to-current conversion efficiency (IPCE) and Faradaic efficiency indicated that Ti-felt/Ti-Fe2O3 showed higher PEC activity for the oxygen evolution reaction (OER) than FTO/Ti-Fe2O3. The enhanced PEC activity is ascribed to the higher donor density and moderate thickness of the Ti-doped Fe2O3 layer, which contribute to a short electron transport distance. Furthermore, the high loading of Fe2O3 on the Ti-felt substrate increased the photoabsorption in the UV and visible light regions and the photocurrent response at wavelengths near the band edge, even at low light intensities. This study provides new insights for preparing hematite photoanodes with higher PEC activity for the OER using a 3D porous substrate, rather than conventional 2D substrates.

Boosting Charge Mediation in Ferroelectric BaTiO3−x‐Based Photoanode for Efficient and Stable Photoelectrochemical Water Oxidation

Oxygen evolution reaction (OER) is a bottleneck to photoelectrochemical (PEC) water splitting; however, there remains an impressive challenge for intrinsic charge transport for the development of integrated photoanodes. Herein, covalent triazine frameworks as conjugated molecules are grafted on the surfaces of ferroelectric BaTiO3−x (CTF/BTO) nanorod array, and then oxyhydroxide oxygen evolution cocatalyst (OEC) is constructed as an integrated photoanode. The OEC/CTF/BTO array not only achieves a high photocurrent density of 0.83 mA cm−2 at 1.23 V versus reversible hydrogen electrode (vs RHE) and low onset potential of ≈0.23 VRHE, but also optimizes outstanding stability. To disclose the origin, the enhanced PEC activity can be contributed to the integration of CTF and OEC, enhancing light‐harvesting capability, boosting charge carrier mediation, and promoting water oxidation kinetics through electrochemical analysis and density functional theory calculations. This study not only provides an alternative to accelerate charge transfer, but also paves the rational design and fabrication of integrated photoanodes for boosting PEC water splitting performance.

Role of conductive channels via CQDs on NiO/g-C3N4 Z-scheme composite as a bi-functional photocatalyst

Herein, an innovative graphitic carbon nitride (g-C3N4) based nanocomposite with nickel oxide (NiO) is modified with carbon quantum dots (CQDs) to fabricate CQD/NiO/g-C3N4 ternary composites. The effect of various concentrations of CQDs is investigated for photo electrochemical (PEC) water splitting and photocatalytic degradation of methyl orange (MO). XRD pattern of CQDs/NiO/g-C3N4 composite showed the distinctive peaks of g-C3N4 and NiO. The reduction of band-gap values from 2.62 to 1.8 eV in UV–Visible spectra of nanocomposites confirmed an improvement toward red shift. The existence of required functional groups and successful fabrication of nanosheets of g-C3N4 and its nanocomposites are confirmed by FTIR. PL confirms the decrease in electron-hole recombination in binary and ternary composites. CQDs/NiO/g-C3N4 (4.0 mL) showed enhanced PEC activity and photocatalytic performance in visible light exposure. CQDs/NiO/g-C3N4 (4.0 mL) showed an obvious enhancement in current density of ∼-19 mAcm−2 at potential 0.39 V during hydrogen evolution reaction (HER) and high current density of ∼ 15 mAcm−2 at 1.42 V in oxygen evolution reaction (OER) than all others. The highest degradation rate of MO by CQDs/NiO/g-C3N4 (4.0 mL) was noted due to availability of plenty of active sites and conductive channels provided by CQDs. Incorporated CQDs in samples affect the overall water splitting response and photocatalytic activity by acting as electron conduction bridge for the quick electron transfer from the composite materials to reaction sites on its surface. This combination is active for efficient PEC water splitting and photo degradation purposes.

Unveiling the activity and stability of BiVO4 photoanodes with cocatalyst for water oxidation

Developing low-cost and efficient cocatalyst is highly desirable for photoelectrochemical (PEC) water oxidation. FeOOH is one of the most typical cocatalysts, the active sites of FeOOH in PEC remain unclear. Herein, the FeOOH was deposited on BiVO4 photoanodes through electrodeposition. A series of experimental evidence shows that the Bi–O–Fe bond is beneficial to the improvement of water oxidation activity, while the FeOOH can not restrain the dissolution of V5+ and improve the stability of the photoelectrode. In order to further improve the activity and stability of BiVO4/FeOOH photoanode, a low-cost metal-organic coordination composed of tannic acid coordinated with Ni ions (TANi) was assembled on the BiVO4/FeOOH (denoted as BiVO4/FeOOH/TANi). Under AM 1.5 G illumination, an impressive current density of 4.6 mA cm−2 (1.23 V vs. RHE) was obtained for BiVO4/FeOOH/TANi photoanode. Systematic studies reveal that the enhanced PEC activity comes from the protection of BiVO4 and enhancement of charge separation efficiency. This work provides a strategy for designing cocatalysts to construct efficient and stable PEC water oxidation.

Fabrication of tin‐doped hematite modified with NiFe‐LDH nanoflakes for highly efficient solar water splitting

Photoelectrochemical (PEC) water splitting is widely regarded as an effective process for sustainable storage of solar energy as chemical energy in the form of H2. The efficiency of this process depends upon the light absorption, charge injection, and charge separation efficiency of the photoanode material used. In this work, doping hematite with 1% tin and loading with NiFe-layered double hydroxide (LDH) co-catalyst has been done to improve the charge transport properties. To enhance the PEC performance and study the effect of precursor concentration, NiFe-LDH at two different concentrations (low and high) was coated on Sn-doped hematite. A high photocurrent density ca. 2.9 mA/cm2 at 1.8 V vs reversible hydrogen electrode (RHE) and a 170 mV cathodic shift in onset potential compared to pristine hematite (0.22 mA/cm2 at 1.8 V vs RHE) was recorded for Sn-doped hematite coated with low precursor concentration. The enhanced PEC activity can be attributed to the synergistic effect of Sn doping and NiFe-LDH co-catalyst on hematite, which contributes to an efficient separation of the photogenerated charge carriers and reduces hole accumulation at the surface. However, for the high precursor concentration case, the formation of a thick film of NiFe-LDH results in a comparatively lower current density (0.85 mA/cm2 at 1.8 V vs RHE). The results obtained show that NiFe-LDH can be used as an effective co-catalyst to significantly enhance the charge transport properties of tin-doped hematite. A charge transfer mechanism of the developed photoanodes is also discussed in detail.

A versatile synthesis strategy and band insights of monoclinic clinobisvanite BiVO4 thin films for enhanced photoelectrochemical water splitting activity

Monoclinic clinobisvanite BiVO4 is one of the promising and extensively researched material for photoelectrochemical (PEC) water splitting. However, no substantial progress has been made to tune the morphology and to explore a wide range of dopants to BiVO4 and heterojunction systems that could affect its PEC activity. Given this, here we propose a versatile BiVO4 thin film synthesis strategy that allows morphology tunability, the feasibility of doping, and heterojunction formation in a single step. The presence of the monoclinic phase was confirmed, and detailed PEC and spectroscopic properties were evaluated to explore water splitting activity and band edge insights. The strategy was extended to fabricate different nanostructures by changing the capping agents and demonstrated the feasibility of Al doping and heterojunction formation with WO3 nanostructure for enhanced PEC activity. Importantly, the proposed strategy could be exploited using new capping agents and dopants for simultaneously obtaining doped BiVO4 in heterojunction systems having unique morphology.

Flexible BiVO4/WO3/ITO/Muscovite Heterostructure for Visible-Light Photoelectrochemical Photoelectrode

Flexible electronics has recently captured extensive attention due to its intriguing functionalities and great potential for influencing our daily life. In addition, with the increasing demand for green energy, photoelectrochemical (PEC) water splitting is a clean process that directly converts solar energy to chemical energy in the form of hydrogen. Thus the development of flexible green energy electronics represents a new domain in the research field of energy harvesting. In this work, we demonstrate the BiVO4 (BVO)/WO3/ITO/muscovite heterostructure photoelectrode for water splitting with flexible characteristics. The performance of BVO was modified by specific crystal facets, and the BVO/WO3 bilayer exhibited superior performance of 33% enhanced PEC activity at 1 V vs Ag/AgCl compared with pure BVO due to the proper staggered band alignment. Moreover, excellent mechanical stability was verified by a series of bending modes. This study demonstrates a pathway to a flexible photoelectrode for developing innovative devices for solar fuel generation.

Ternary Cu2SnS3: Synthesis, Structure, Photoelectrochemical Activity, and Heterojunction Band Offset and Alignment.

Ternary Cu2SnS3 (CTS) is an attractive nontoxic and earth-abundant absorber material with suitable optoelectronic properties for cost-effective photoelectrochemical applications. Herein, we report the synthesis of high-quality CTS nanoparticles (NPs) using a low-cost facile hot injection route, which is a very simple and nontoxic synthesis method. The structural, morphological, optoelectronic, and photoelectrochemical (PEC) properties and heterojunction band alignment of the as-synthesized CTS NPs have been systematically characterized using various state-of-the-art experimental techniques and atomistic first-principles density functional theory (DFT) calculations. The phase-pure CTS NPs confirmed by X-ray diffraction (XRD) and Raman spectroscopy analyses have an optical band gap of 1.1 eV and exhibit a random distribution of uniform spherical particles with size of approximately 15–25 nm as determined from high-resolution transmission electron microscopy (HR-TEM) images. The CTS photocathode exhibits excellent photoelectrochemical properties with PCE of 0.55% (fill factor (FF) = 0.26 and open circuit voltage (Voc) = 0.54 V) and photocurrent density of −3.95 mA/cm2 under AM 1.5 illumination (100 mW/cm2). Additionally, the PEC activities of CdS and ZnS NPs are investigated as possible photoanodes to create a heterojunction with CTS to enhance the PEC activity. CdS is demonstrated to exhibit a higher current density than ZnS, indicating that it is a better photoanode material to form a heterojunction with CTS. Consistently, we predict a staggered type-II band alignment at the CTS/CdS interface with a small conduction band offset (CBO) of 0.08 eV compared to a straddling type-I band alignment at the CTS/ZnS interface with a CBO of 0.29 eV. The observed small CBO at the type-II band aligned CTS/CdS interface points to efficient charge carrier separation and transport across the interface, which are necessary to achieve enhanced PEC activity. The facile CTS synthesis, PEC measurements, and heterojunction band alignment results provide a promising approach for fabricating next-generation Cu-based light-absorbing materials for efficient photoelectrochemical applications.

Sulfur-doped graphitic carbon nitride incorporated bismuth oxychloride/Cobalt based type-II heterojunction as a highly stable material for photoelectrochemical water splitting

Cobalt incorporated sulfur-doped graphitic carbon nitride with bismuth oxychloride (Co/S-gC3N4/BiOCl) heterojunction is prepared by an ultrasonically assisted hydrothermal treatment. The heterojunction materials have employed in photoelectrochemical (PEC) water splitting. The PEC activity and stability of the materials are promoted by constructing an interface between the visible light active semiconductor photocatalyst and cocatalysts. The photocurrent density of Co-9% S-gC3N4/BiOCl has attained 393.0 μA cm−2 at 1.23 V vs. RHE, which is 7-fold larger than BiOCl and ~3-fold higher than 9% S-gC3N4/BiOCl. The enhanced PEC activity can be attributed to the improved electron-hole charge separation and the boosted charge transfer is confirmed by photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) analysis. The fabricated Co/S-gC3N4/BiOCl nanohybrid material has exhibited high stability of up to 10,800 s (3 h) at 1.23 V vs. RHE during PEC water splitting reaction and the obtained photo-conversion efficiency is 3.7-fold greater than S-gC3N4/BiOCl and 17-fold higher than BiOCl. The FESEM and HRTEM images have revealed the formation of heterojunction interface between S-gC3N4 and BiOCl and the elemental mapping has confirmed the presence of cobalt over S-gC3N4/BiOCl. The heterojunction interface has facilitated the photo-excited charge separation and transport across the electrode/electrolyte interface and also the flat-band potential, which is confirmed by Mott-Schottky analysis.

Synergy effect of Ag plasmonic resonance and heterostructure construction enhanced visible-light photoelectrochemical sensing for quercetin

A novel heterojunction, on the basis of Ag doped zinc oxide nanorods (Ag–ZnO NRs) coupled with nickel cobalt layered double hydroxides (NiCo-LDHs), has been designed and prepared via a hydrothermal method followed by electrodeposition technique on F-doped SnO2 conducting glass (FTO) substrates. The morphology, compositions, optical and photoelectrochemical (PEC) performance were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, UV–vis spectroscopy, infrared spectroscopy, photoluminescence spectroscopy and PEC technique. The prepared NiCo-LDHs/Ag-ZnO NRs/FTO electrode exhibited a significantly enhanced PEC activity owing to the synergy effect of the surface plasmonic resonance of Ag nanoparticles and the heterostructure construction. The as-prepared electrode showed enhanced PEC quercetin (Qu) sensing performance under visible light irradiation. A broad linear range for Qu was obtained in the range of 1.0 × 10−10~5.0 × 10−6 mol/L and the detection limit was lowered to 0.075 nmol/L. Additionally, the PEC sensing platform for Qu exhibited advanced performances with high selectivity, good reproducibility and stability. The present work provides a new approach for the design of a PEC sensor for the detection of Qu in the practical applications.

Promoting Photoelectrochemical Activity and Stability of WO3/BiVO4 Heterojunctions by Coating a Tannin Nickel Iron Complex

Achieving enhanced photoelectrochemical (PEC) activity and stability of a photoanode remains as a formidable challenge. In this study, a porous tannin nickel iron complex coated WO₃/BiVO₄ heterojunction (WO₃/BiVO₄@TANiFe) is constructed to achieve enhanced PEC activity and stability. The in situ construction of a type-II heterostructure is highly beneficial for broad visible light utilization and efficient separation of photogenerated carriers. In addition, the intact coating of ultrathin tannin nickel iron nanolayer could not only accelerate the reaction kinetics of water oxidation but also safeguard the semiconductors from photocorrosion during the PEC reaction. As a result, the as-designed WO₃/BiVO₄@TANiFe ternary photoelectrode exhibits an outstanding photocurrent density of 3.7 mA cm–² at 1.23 V vs RHE with substantially enhanced running durability at high photocurrent density. The present study would provide a rational route for developing highly active and stable photoanodes for solar-energy conversion applications.

Efficient BiVO4 photoanode decorated with Ti3C2TX MXene for enhanced photoelectrochemical sensing of Hg(II) ion

A highly sensitive photoelectrochemical (PEC) sensing platform was constructed for Hg2+ determination based on the Schottky heterojunction between an emerging 2D material Ti3C2TX MXene and a promising semiconductor material BiVO4. Through simply spin-coating the single-layer Ti3C2TX onto the surface of BiVO4 film, the modified electrode exhibited significantly enhanced PEC activity. However, the boost in photocurrent could be noticeably suppressed due to the consumption of hole-scavenging agents (reduced glutathione) by the added Hg2+. Owing to the selective decrease in the photocurrent with the addition of Hg2+, the PEC sensor based on BiVO4/Ti3C2TX displayed a wide linear range from 1 pM to 2 nM with the limit of detection down to 1 pM. Moreover, the PEC sensor also exhibited satisfactory accuracy and repeatability in practical sample water, the Yangtze River water, demonstrating the great potential for monitoring heavy metal ions in natural water resources.