Photoelectrochemical Performance Research Articles

(Invited) Design Rules for (Li-mediated) Photoelectrochemical N2 Reduction to NH3

The electrochemically-driven N2 reduction reaction (N2RR) offers an alternative route to the traditional Haber-Bosch method for production of NH3. Electrifying NH3 synthesis promises a route to the decarbonization and decentralization of ammonia production, which currently accounts for >1% of annual CO2 emissions. While there have been many studies examining electrochemically-driven production of NH3 in aqueous electrolytes at low-T (≤ 50o C) and low-P (≤20 bar), lithium-mediated N2 reduction (Li-N2R) in nonaqueous electrolytes at low-T and low-P has emerged as a promising method for obtaining reliable electroreduction of N2 to NH3.With this in mind, our team at SUNCAT and NREL have begun evaluating the opportunity and key design rules necessary for coupling photoelectrochemical methods to the drive the Li-N2R reaction using solar illumination. Nonaqueous, photoelectrochemical Li-N2R promises a route to stable operation that has been a key challenge associated with photoelectrode operation in aqueous electrolytes. Recognizing the energetic constraints associated with the Li-mediated process, we have modeled and mapped the bandgap characteristics necessary for a semiconducting light absorber to drive the Li-N2R reaction and the maximum attainable solar-to-NH3 conversion yields. We have identified III-V based photoelectrodes that meet the modeled requirements and evaluated the surface chemistry at the electrode/electrolyte interface under Li-N2R conditions to understand the how reactive Li-species influence photoelectrochemical performance (e.g., rate, selectivity, stability), how solid-electrolyte interface (SEI) formation and electrolyte selection are mutually influenced by illumination, and how the current density and cycling conditions enforced by solar operation dictate photoelectrochemical N2-to-NH3 performance. We have further extended a neutron-reflectometry technique used for in situ observation of interfacial layer formation to be compatible with light-driven reactions, and with these insights in hand continue our drive toward demonstrating unassisted photoelectrochemical N2-to-NH3 production.

(Invited) Unraveling Hot Carrier Transfer Processes in Plasmonic Catalysis

In the last decade, plasmonic nanoantennas have revolutionized light manipulation and control at the nanoscale. Interestingly, generation of hot carriers in metals upon light absorption have opened new pathways for controlling photo(electro)chemical processes and engineering photocatalysts. Yet, fundamental questions remain about the microscopic details of these complex light-matter interactions.We have recently developed a well-controlled platform for micro-scale plasmonic photoelectrochemistry studies that leverages the unique properties of monocrystalline microflakes [1] as well as precise nanofabrication methods. Interestingly, the microflakes exhibit well-defined crystal facets and can bridge the properties of bulk metals with those of nanoscale plasmonic antennas, accessing ultra-thin film dimensions (sub 15-nm) that are challenging for polycrystalline films. By performing careful absorption measurements, we explore the photoelectrochemical performance of these hot carrier micro-scale photoelectrodes for inner- and outer-sphere reactions [2], concurrently comparing them to cm-scale devices [3]. This allows us to unravel the interplay of hot carrier generation and transport at metal-liquid and metal-semiconductor interfaces and identify bottlenecks for charge transfer.[1] Kiani F., Tagliabue G. - High‐Aspect Ratio Au Microflakes via Gap‐Assisted Synthesis – Chemistry of Materials 34 (3), 1278-1288, 2022[2] Kiani F. et al - Transport and Interfacial Injection of d-band Hot Holes Control Plasmonic Chemistry - ACS Energy Letters, 8 (10), 4242-4250, 2023[3] Ma J., Oh K., Tagliabue G. - Understanding Wavelength-Dependent Synergies between Morphology and Photonic Design in TiO2-Based Solar Powered Redox Cells – Journal of Physical Chemistry C, 127 (1), 11-21, 2022

Porous Bismuth Vanadate Photoelectrodes for Solar Water Oxidation Reaction

Bismuth vanadate (BiVO4), a material known for its high visible light activity and good stability, is a promising candidate as a photoanode for overall water splitting [1]. Its performance is limited by its relatively short charge carrier diffusion length, which has recently been estimated to be ~15 nm [2]. For these kinds of photo-absorbers, commercial flat transparent conducting oxide (TCO) substrates are unsuitable since the thickness needed to absorb a sufficient amount of light far exceeds the carrier diffusion length. With this in mind, deposition of very thin semiconductor film onto the internal structure of (micro)porous, conducting substrates can ensure sufficient light absorption [3], whilst ensuring the individual film thickness is uniformly lower than the carrier diffusion length. Nanostructured TCO substrates can be fabricated using a convenient template-free technique called glancing angle deposition (GLAD). The glancing angle deposition method can be used to synthesize different variations of highly oriented submicron-sized pillars, ranging from vertical and tilted columns to zig-zag and helical structures with the help of shadowing effects and substrate rotation [4]. The optical and electrical properties of nanostructured TCO’s were found to depend on the type of material and the substrate temperature during deposition. We find that pillars made from tin-doped indium oxide show good conductivity (79 Ohm/sq) and are promising for the fabrication of nanostructured substrates for bismuth vanadate. A recently developed alternative approach is the use of transparent, porous, conducting substrates (TPCS) made from quartz felt, in which the quartz fibers are coated with F-doped SnO2 [5]. We found that a BiVO4 film thickness of 50 nm within these porous substrates is enough to absorb the same amount of light as a compact 400 nm bismuth vanadate film. We will discuss the deposition of BiVO4 into the TPCS substrates and the photoelectrochemical performance of these porous photoanodes.[1] K. Sivula and R. van de Krol, Nat. Rev. Mater. 1, 15010 (2016)[2] M. Schleuning, M. Kölbach, F. F. Abdi, K. Schwarzburg, M. Stolterfoht, R. Eichberger, R. van de Krol, D. Friedrich, H. Hempel, PRX Energy 1, 023008 (2022)[3] U. Björksten, J. Moser and M. Grätzel, Chem. Mater. 6, 858 (1994)[4] M. M. Hawkeye, M. T. Taschuk and M. J. Brett, “Glancing Angle Deposition of Thin Films”, John Wiley & Sons, Ltd., Chichester, UK (2014).[5] M. Caretti, E. Mensi, R.-A. Kessler, L. Lazouni, B. Goldman, L. Carbone, S. Nussbaum, R. A. Wells, H. Johnson, E. Rideau, J.-h. Yum, K. Sivula, Adv. Mater. 35, 2208740 (2023)

Maximizing Quantum Hole Collection on Anatase TiO2 Thin Films with (001) Facets for Photoelectrochemical Oxigen Evolution Reaction Efficiency

Hydrogen production from water, a key element in the renewable energy portfolio, offers a solution to reduce reliance on fossil fuels. Photoelectrochemical (PEC) hydrogen production, using light-absorbing semiconductors and catalysts, offers a clean and cost-effective method for harnessing solar energy. To enhance the efficiency of PEC, this study explores the use of anatase TiO2 thin film photoelectrodes as an alternative to expensive and rare catalysts, aiming to generate hydrogen as a clean fuel with oxygen as a byproduct.Anatase titanium dioxide is a well-established functional material widely applied in the fields of environment and energy. Recognized as one of the premier materials for photocatalysis and a promising photoanode material for water splitting, titanium dioxide (TiO2) finds use in diverse applications such as dye-sensitized solar cells, perovskite-based solar cells, and cleaning devices. Its band gap of 3.2 eV, stability, strong absorption in the UV region, and energetics of the valence and conduction band edges make anatase particularly suitable for PEC water splitting, especially for the oxygen evolution reaction (OER).Our research focuses on the development of anatase thin films with strong [001] texture and (001) facets at the surface of the film. The (001) facets are known to accumulate photogenerated hole states while the [001] orientation imparts a negative flat band potential. We hypothesize that these two properties, (001) facets and [001] texture, are ideal for OER. This study combines these two structural characteristics within the semiconductor TiO2 layer to enhance PEC performance and maximize the efficiency of hole collection during water oxidation.Anatase TiO2 thin films with (001) facets and [001] orientation were hydrothermally synthesized on a fluorine-doped tin oxide (FTO) substrate and annealed at 500°C. The films exhibited [001] orientation and (001) faceting as shown by grazing incidence X-ray diffraction (GI-XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Photoelectrochemical measurements via cyclic voltammetry in a 0.1 M KOH and Na2SO3 solution demonstrated the films' hole collection efficiency under a 365 nm UV light source. The photoelectrochemical (PEC) and oxygen evolution reaction (OER) characteristics of anatase thin films were observed both under dark and light conditions. Prior to illumination, only the Ti3+/Ti4+ redox couple was observed with an onset potential of 0.01 V (RHE) and negligible OER at anodic potentials. When UV irradiated, the TiO2 thin films exhibited a photocurrent that increased through the anodic scan. The onset potential of photocurrent, measured in the presence of the hole scavenger, exhibited a negative shift ranging from -100 to -200 mV compared to the KOH onset potential. This shift is attributed to the film surface's limited efficiency in collecting holes for water oxidation at low potentials, as rapid recombination kinetics compete with water oxidation. Interestingly, the photocurrent observed with Na2SO3 electrolyte was 0.15 to 0.3 times more than what we saw with KOH electrolyte. Our preliminary results indicate a current density of ~2.0-2.5 mA cm-2 at 1.8 V and a hole collection efficiency of ~84 % at 1.23 V vs RHE, the thermodynamic water oxidation potential. In summary, we have made significant progress toward enhancing the PEC activity of anatase TiO2 thin films by optimizing the film structure for both reactivity and charge transport.

Oxidation of Ethylene Glycol into Valuable Chemical Using BiVO4 Photoanode

Introduction Plastic photoreforming using photocatalysts is a solar-powered technology that facilitates the generation of hydrogen (H2) from water while simultaneously breaking down plastic waste into valuable organic products. While the focus in the past few decades has predominantly centered on enhancing the H2 production efficiency, recent attention has shifted towards selective plastic oxidation reactions (U. Nwosu, et al. Renew. Sust. Energ. Rev. , 2021, 148, 111266). However, the investigation of effective cocatalysts for selective oxidation of plastic compounds has not been well studied.The photoelectrochemical (PEC) system offers a promising approach by segregating the anodic and cathodic processes, thereby enabling a more concentrated focus on the oxidation reaction in the design of reactions. In this study, we evaluate the BiVO4 photoanode modified with various cocatalysts, for example, cobalt phosphate (Co-Pi) for the oxidation of ethylene glycol (EG), a crucial component in the formation of polyethylene terephthalate (PET). Additionally, we introduce acetonitrile (MeCN) into the reactant mixture to suppress the oxygen evolution reaction (OER), which otherwise competes with the ethylene glycol oxidation reaction (EGOR), creating a more conducive reaction environment for enhanced efficiency. Materials and Methods The BiVO4 photoanode on fluorine doped tin oxide (FTO) glass was fabricated as previously reported (V. Andrei, et al. Adv. Energy Mater , 2018, 8, 1801403). Briefly,BiOI precursor was electrochemically deposited on the FTO glass and then drop-casted a vanadyl acetylacetonate [VO(acac)2] solution onto the surface and heated at 723 K for 60 min. The deposition of the Co-Pi cocatalyst onto BiVO4 was achieved by photoassisted electrodeposition method. The obtained photoanodes were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). PEC measurements were carried out using a three-electrode configuration under simulated solar irradiation (100 mW cm− 2, AM 1.5G). The experiments were performed in various solutions containing 1 M EG: 0.5 M Na2SO4 in H2O, 0.1 M NaClO4 in MeCN, and the mixed solution of MeCN and H2O. Product analysis was performed using proton nuclear magnetic resonance (1H NMR). Results and discussion According to the XRD and SEM results, the formation of nanoporous BiVO4 film on FTO glass was confirmed. To assess the PEC performance for EGOR using BiVO4 electrode, we carried out the experiments under conditions with and without the EG substrate (Figure (a)). With the addition of EG, a notable shift of the onset potential from 0.6 VRHE to 0.5 VRHE was observed. In addition, the photocurrent density at 1.2 VRHE increased from 0.67 mA/cm2 to 0.92 mA/cm2. This result indicates that EGOR is more favorable on the BiVO4 surface compared to OER. The Co-Pi cocatalyst deposition on the BiVO4 notably increased the current under both conditions, with and without the EG substrate. Although Co-Pi is commonly recognized for its catalytic role in OER, our experiment surprisingly revealed its positive impact on EG performance as well. The Co-Pi/BiVO4 photoanode exhibited a negative shift of the onset potential to 0.3 VRHE and an enhancement of photocurrent density to 2.04 mA/cm2 at 1.2 VRHE for EGOR compared to bare BiVO4. Additionally, the Co-Pi/BiVO4 photoanode showed 16.9% and 2.7% faradaic efficiencies (FE) for formate and glyoxal production, respectively, while bare BiVO4 exhibited 10.6% FE for formate and no glyoxal production.Under aqueous conditions, the FE for EGOR is currently low due to the competition between OER and EGOR. To overcome this challenge and enhance the EGOR efficiency, we introduced MeCN into the aqueous solution because MeCN has higher (more positive) anodic oxidation potential than the aqueous medium (L. M. Reid, et al. Sustainable Energy Fuels , 2018, 2, 1905-1927). In the MeCN-water mixed solution (MeCN:water = 9:1), OER was effectively suppressed to 0.33 mA/cm2, while EGOR was significantly enhanced to 2.50 mA/cm2 at 1.2 VRHE potential (Figure (b)). This MeCN-water mixed solvent created a more favorable environment for EGOR on bare BiVO4, resulting in a notable increase in FE for formate to 19.8% and FE for glyoxal to 13.2%, which represents a 1.87 and 4.89 times improvement, respectively, compared to the pure aqueous condition. Conclusions The deposition of Co-Pi cocatalyst on the BiVO4 film improved the photocurrent density and FE for formate production. Moreover, the introduction of MeCN in the solvent created a more favolable reaction condition for EGOR, suppressing OER and increasing the EGOR activity. Figure 1

Construction of heterojunctions with in situ growth of ZnIn2S4 nanosheets on the surface of atomically dispersed Cu-modified MOFs for high-performance visible-light photocatalytic antibiotic degradation

Metal-organic frameworks (MOFs) are ideal candidates for obtaining composites with excellent photocatalytic properties due to their reasonable band gaps and high specific surface area. In this study, Cu@UiO-66-NH2@ZnIn2S4 nanocomposites were prepared by a two-step photoinduction method and hydrothermal method. The prepared catalysts in a range of ratios showed high visible light degradation of tetracycline hydrochloride (TC). Among them, 10%-Cu@UIO-66-NH2/ZnIn2S4 showed the best catalytic activity and photoelectrochemical performance. In this catalytic system, the high specific surface area and porosity of UIO-66-NH2 provide sites for the high dispersion of Cu. In addition, the introduction of Cu also reduces the band gap, which is conducive to the electron transfer between the interfaces, which results in the formation of type II heterojunctions with a unique and highly efficient electron transfer mechanism, and also enables the photocatalytic process to generate more active radicals (O2–, OH, h+). In addition, the stability of the catalyst was tested, as well as the possible degradation pathways were hypothesized to evaluate its toxicity. Thus, this study provides a strategy for the preparation of stable and efficient photocatalysts..

Ternary nanostructure of CdS-rGO-Ag for enhanced photoelectrochemical application.

In the present study, we have synthesized the ternary nanostructure of CdS-rGO-Ag by using the solvothermal method for the enhanced photocatalytic as well as electrocatalytic activity of the material. The optical properties of the prepared samples were characterized by using UV-visible spectroscopy and photoluminescence (PL) spectroscopy. A decline in the energy gap of CdS-rGO-Ag nanostructure to 1.90 ± 0.05 from 2.40 ± 0.08eV (CdS) is observed and may be attributed due to the rGO-Ag-induced creation of trap states in between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of CdS. The observed significant PL quenching also confirms the inclusion of trap states in the prepared nanostructure CdS-rGO-Ag, suggesting efficient photoactivity. The enhanced photocatalytic activity of CdS-rGO-Ag for methylene blue (MB) dye degradation supports the photocatalytic activity of prepared nanostructures. Furthermore, the photoelectrochemical catalytic activity of the CdS-rGO-Ag catalyst investigated by using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) depicts the improved current density, lowering of overpotential. The decrement in charge transfer resistance and enhancement in photocurrent density under light illumination indicates the better photoelectrochemical performance of CdS-rGO-Ag.

CuO nanoparticles for enhanced photoelectrochemical HER activity

Cupric oxide nanoparticles are a p-type semiconductor that can be used as a hole transport layer material in perovskite solar cells owing to their high electrical conductivity and stability. In the present work, CuO nanoparticles are synthesized using the hydrothermal technique, and their photoelectrochemical properties are studied through cyclic voltammetry. The X-ray diffraction patterns of the nanoparticles were analyzed for phase formation, revealing the monoclinic phase and further verified by the Rietveld Refinement. Thermogravimetric analysis shows a total weight loss of 13.47%. Transmission electron microscopy analysis suggests the formation of nanoparticles with an average size of 34 nm. The selected area electron diffraction analysis reveals the crystalline structure of the nanoparticles. The absorbance spectra of the nanoparticles were analyzed by UV–visible measurement, and Tauc's relation was used to estimate the optical bandgap. The XPS results align with the XRD results, indicating the formation of pure CuO nanoparticles. The developed catalyst's photoelectrochemical performance was investigated in the neutral solution for the hydrogen evolution reaction activity, and a high photocurrent density of −41.57 mA/cm2 was observed versus −0.6 V vs. RHE.

Electrolyte and interfacial engineering for self-formation of In₂S₃/In₂O₃ heterojunction with an enhanced photoelectrochemical activity

Electrolyte and interfacial engineering of photoanodes has become a crucial approach to enhance photoelectrochemical water-splitting performance. By optimizing both the electrolyte and the interfacial properties of the photoanode, the synergistic effects of the heterojunction and electrolyte can be leveraged to improve efficiency. In this work, we explore the crucial role of electrolyte and interfacial engineering in optimizing photoanode performance. By engineering an In2O3 film in a polysulfide electrolyte to form an in-situ In₂S₃/In₂O₃ heterojunction interface, we demonstrate a significant increase in anodic photocurrent compared to traditional aqueous Na2SO4 or NaOH electrolytes. This enhancement is attributed to both the thermodynamically favorable oxidation of sulfide and sulfite, and the unique electronic structure developed at the In₂S₃/In₂O₃ junction, which significantly improves charge separation and overall performance. Based on this finding, an efficient In₂S₃/In₂O3 heterojunction interface through optimal anion exchange with sulfur was developed, leading to a maximum photocurrent density of 5.57 mA cm−2 in the polysulfide electrolyte. In addition, detailed structural, optical, and photoelectrochemical properties of the In₂S₃/In₂O₃ interface providing insights into the mechanisms underlying the enhanced water-splitting performance have also been discussed.

Regulating coordinatively unsaturated Co active sites in TA@ZIF-L(Co) via tannic acid for efficient photoelectrochemical water oxidation

Metal-organic frameworks (MOFs) as a cocatalyst can enhance the photoelectrochemical (PEC) water oxidation performance to a certain extent, but still suffer from deficient exposure of active sites and low electron mobility. In this work, 2D Leaf-like zeolitic imidazolate frameworks (ZIF-L) were selected as a precursor for the generation of defective structures by tannic acid (TA) functionalization-assisted etching, and then coupling it with BiVO4 to prepare a novel and highly efficient TA@ZIF-L(Co)/BiVO4 photoanode by a simple impregnation method. The photocurrent density of TA@ZIF-L(Co)/BiVO4 composite photoanode achieves 4.21 mA cm−2 at 1.23 VRHE under AM 1.5 G illumination, which is superior to that of ZIF-L(Co)/BiVO4, and three times that of the bare BiVO4, with a charge injection efficiency of up to 80 %, and its stability is also remarkably improved. Experimental results and DFT calculations showed that the introduction of TA not only improved the light absorption efficiency, but also exposed more active sites, increased the electron density of the coordinatively unsaturated Co active sites, and enhanced the polarized electric field on the surface, thus accelerating electron mobility. This work demonstrates that TA as a surface modifier has great potential to activate metal sites and change the electronic environment of MOFs for BiVO4-based photoanode in PEC water oxidation, providing valuable insights into the rational design of photoanodes.

Rare earth oxide Y2O3 modified g-C3N4 for efficient photocatalytic hydrogen production: photocatalytic performance and electron transfer channels

This work used a one-step calcination process to prepare g-C3N4 composites with varying Y2O3 loading. XRD, TEM, and XPS verified the structure and morphology of the composite photocatalyst, and its photoelectrochemical and hydrogen production performance were studied. According to the experimental results, it is found that the composite structure between Y2O3 and g-C3N4 effectively suppresses the photoelectron–hole complex and enhances the photocatalytic hydrogen production properties of g-C3N4. Under the irradiation of a 300 W xenon lamp, YCN-3 had superior photocatalytic hydrogen generation performance, achieving a rate of 1079.61 μmol g−1 h−1, which was 2.3 times greater than that of g-C3N4 in its unmodified state. After three consecutive photocatalytic operations, satisfactory stability and reusability were obtained. Finally, the possibility of a mechanism for the photocatalytic charge transfer pathway is discussed, which provides an effective way for g-C3N4 photocatalytic hydrogen production.

Improving light harvesting and charge carrier separation enabling enhanced photoelectrochemical hydrogen production by Sb2S3-decorated TiO2 nanotube arrays on porous Ti-photoanodes

The Ag + ions doped TiO2 nanotube arrays fabricated on Ti mesh through an electrochemical anodization process, and n/n heterostructure formed by coating the TiO2 nanotube array photoanode with an n-type stibnite (Sb2S3) layer improve photoelectrochemical water splitting reaction by enhancing light harvesting and charge carrier separation. Sb2S3 is chosen because of its suitable band gap position and strong visible light response. The Ag + ion incorporated TiO2 nanotube array coated with Sb2S3 exhibits a photocurrent density of 6.5 mA cm−2 vs. RHE, whereas bare TiO2 nanotube array coated with Sb2S3 and pristine TiO2 nanotube array exhibit photocurrent densities of 3.6 and 0.27 mA cm−2, respectively, under the same conditions, which is nearly 1.8 and 24 times greater than the TiO2 nanotube array coated with Sb2S3 and pristine TiO2 nanotube array photoanodes. The applied bias photon-to-current efficiency of Ag + ion incorporated TiO2 nanotube array coated with Sb2S3 is 3.6% and the improved Photoelectrochemical performance of Ag + ion doped TiO2 nanotube array coated with Sb2S3 is attributable to higher conductivity of TiO2 nanotube array caused by increased oxygen vacancies and broad optical activity of Sb2S3. The 1-dimensional TiO2 nanotube array device structure in the Ti mesh improves charge separation and light harvesting while reducing photogenerated charge carrier recombination and the potential of this novel device structure for advanced energy conversion applications is highlighted in this study.

Facile Exfoliation of Few-Layer Sn-Based Nanosheets for Self-Powered Photo-Electrochemical and All-Optical Modulation Applications.

Few-layer tin (Sn)-based nanosheets (NSs) with a thickness of ≈2.5nm are successfully prepared using a modified liquid phase exfoliation (LPE) method. Here the first exploration of photo-electrochemical (PEC) and nonlinear properties of Sn NSs is presented. The results demonstrate that the PEC properties are tunable under different experimental conditions. Additionally, Sn NSs are shown to exhibit a unique self-powered PEC performance, maintaining a good long-term stability for up to 1 month. Using electron spin resonance, active species, such as hydroxyl radicals (·OH), superoxide radicals (·O2 -), and holes (h+), are detected during operations, providing a deeper understanding of the working mechanism. Furthermore, measurements of nonlinear response reveal that Sn NSs can be effective for all-optical modulation, as it enables the realization of all-optical switching through excitation spatial cross-phase modulation (SXPM). These findings present new research insights and potential applications of Sn NSs in optoelectronics.

Green light all the way: Triple modification synergistic modification effect to enhance the photoelectrochemical water oxidation performance of BiVO4 photoanode

The recombination of photogenerated electron-hole pairs of the photoanode seriously impairs the application of bismuth vanadate (BiVO4) in photoelectrochemical water splitting. To address this issue, we prepared a Yb:BiVO4/Co3O4/FeOOH composite photoanode by employing drop-casting and soaking methods to attach Co3O4/FeOOH cocatalysts to the surface of ytterbium-doped BiVO4. The prepared Yb:BiVO4/Co3O4/FeOOH photoanode demonstrates a high photocurrent density of 4.89 mA cm−2 at 1.23 V versus the reversible hydrogen electrode (RHE), which is 5.1 times that of bare BiVO4 (0.95 mA cm−2). Detailed characterization and testing demonstrated that Yb doping narrows the band gap and significantly enhances the carrier density. Furthermore, Co3O4 serves as a hole transfer layer to expedite hole migration and diminish recombination, while FeOOH offers additional active sites and minimizes surface trap states, thus boosting stability. The synergistic effects of Yb doping and Co3O4/FeOOH cocatalyst significantly improved the reaction kinetics and overall performance of PEC water oxidation. This work provides a strategy for designing efficient photoanodes for PEC water oxidation.

A photoelectrochemical immunosensor based on cobalt corrole sensitized carbon nitride for human norovirus detection

Norovirus (NoV) stands as the prevailing etiological agent behind childhood gastroenteritis and foodborne illness, garnering significant attention due to its high infectivity pathogenicity. Protruding domain within the capsid protein (VP1) emerges as the primary antigenicity determinant and a hypervariable region, presenting a potential target site for detecting NoV infection. Herein, a label-free photoelectrochemical (PEC) immunosensor was proposed to achieve high sensitivity toward VP1, utilizing Co-Corrole sensitized carbon nitride (Co-Corrole/CN). Co-Corrole combines with CN through covalent bonds, and the strong binding effect accelerates the directional transport of electrons from CN to Co-Corrole. Co-Corrole acts as a photosensitizer, enhancing light harvesting in the visible region. The well-defined interfacial contact in Co-Corrole/CN heterojunction facilitates the electron-hole pairs separation and transfer. The strong light utilization and efficient carrier migration improve the PEC performance to amplify the photocurrent. This developed immunosensor platform demonstrated a wide range (0.75 pg mL–1-150 ng mL–1) with a notably low limit of detection (0.25 pg mL–1), exhibiting excellent stability and selectivity for other viruses. Moreover, this sensor detected clinical samples with remarkable accuracy and practicability. This research develops a facile and label-free diagnostic analytical technology for highly sensitive detection of NoV VP1 and offers promising prospects for improved diagnostic capability.

G-C3N4 hollow tubes decorated with SnO2 quantum dots for photoelectrochemical applications

Graphitic carbon nitride (g-C3N4) has been widely used to improve photoelectrochemical (PEC) activity owing to its outstanding photoresponse and strength. In this study, g-C3N4 hollow tubes decorated with SnO2 quantum dots were prepared by combining hydrothermal and post-annealing approaches. In particular, different characterization techniques such as Fourier transform infrared, photoluminescence, ultraviolet–visible, and X-ray photoelectron spectroscopies were employed to investigate the electrical and optical behaviors of the samples. The prepared samples exhibited considerable photoresponse and excellent PEC performance, producing hydrogen. Furthermore, the heterostructures among SnO2 and g-C3N4 encouraged carrier separation, improving the PEC ability. In addition, the applied voltage showed numerous effects on generating charge carriers for the anodes in a 0.1 M sodium hydroxide electrolyte. Therefore, the proposed approach is simple and effective and can be used to enhance the performance of the PEC activity.

Anchoring Cu2O onto WO3 by adsorption-ascorbic acid reduction: A p-n junction with improved photocatalytic and photoelectrochemical properties

Tungsten trioxide is a promising photoelectric material owing to its abundant structures and unique properties, but the serious photogenerated charge recombination limits its photocatalytic and photoelectrochemical performance. Herein, 0D Cu2O was anchored onto 3D WO3 in-situ via a facile adsorption-ascorbic acid reduction method at room temperature. The coupling of WO3 with Cu2O produces improved charge separation efficiency, thereby the photocatalytic degradation rate and transient photocurrent of optimal WO3/Cu2O are 2.7 and 1.6 times higher than those of WO3, respectively. The enhanced performance is ascribed to the formation of a p-n heterojunction, which was demonstrated by experimental characterizations and theoretical calculation.

Plasmon-induced electron transportation in heterostructure N-rGO/NiFe-LDH@Au with enhanced photoelectrochemical water oxidation

Facile design and fabrication of an ideal heterointerface model is considered as a significant advancement towards photoelectrochemical (PEC) water splitting efficiency. Here, we detail the incorporation of plasmonic Au nanoparticles into N-doped reduced graphene oxide/NiFe-layered double hydroxide (N-rGO/NiFe-LDH) interface by cost-effective coprecipitation-photoreduction method and photoelectrode assemblage via drop casted technique for enhanced PEC water oxidation. Au nanoparticles efficiently harvest the light energy upon plasmonic excitation and transfer the energy towards contacted NiFe-LDH and N-rGO, thereby promoting PEC performances. In comparison to N-rGO/NiFe-LDH, the as-obtained N-rGO/NiFe-LDH@Au composite exhibits 1.46 fold times enhancement in photocurrent density (5.7 mA/cm2 at 1.23 V vs RHE) and considerable cathodic shift of 20 mV at onset potential of 0.18 V for PEC water oxidation. Additionally, N-rGO/NiFe-LDH@Au exhibits incident photon to current conversion efficiency (IPCE) of 10 % and better photostability of more than 6 h for boosted water splitting. The incorporation of Au nanoparticles significantly augmented the photoactivity as apparent from the photocurrent density assessment. The improved PEC performance of N-rGO/NiFe-LDH@Au photoelectrode is accredited to the surface plasmon resonance (SPR) induced electron transfer process and heterostructure configuration holding numerous defect sites for smooth charge transportation. This fabrication approach is quite a simplistic method to enlarge the optical behavior and effective performance of the PEC system and also provide guidance to assemble other sophisticated materials suitable for the energy conversion process.

Optical, dielectric and photoelectrochemical performances of the CeO2/silicon nanowire system: Studying the silicon nanowire length effect on the photodegradation of rhodamine B

Optical, dielectric and photoelectrochemical performances of the CeO2/silicon nanowire system: Studying the silicon nanowire length effect on the photodegradation of rhodamine B

Tetragonal/orthorhombic phase Bi2WO6 homojunction for photoelectrochemical degradation of rhodamine B with high efficiency

Photoelectrochemical (PEC) degradation of organic pollutants to CO2 and H2O is a promising strategy to solve the growing environmental problems. Bismuth tungstate (Bi2WO6) has attracted much attention due to its good chemical stability and moderate conduction band valence band position. However, the PEC activity of Bi2WO6 catalysts is greatly limited due to its rapidly complex electron-hole. This article reports a rational low-cost design that successfully prepares tetragonal/orthorhombic Bi2WO6 homojunction on FTO conductive glass substrates through a simple two-step solvothermal method, significantly enhancing the PEC performance. The study investigated the effectiveness of photoelectrochemical degradation of the recalcitrant organic pollutant Rhodamine B (RhB) and conducted an in-depth exploration of the photoelectrocatalytic reaction process and mechanism. The experimental results indicate that the homojunction achieves a degradation rate of up to 100 % for the recalcitrant organic pollutant RhB within 30 minutes, significantly surpassing that of single-phase Bi2WO6, and at the same time the sample maintains good stability after five cycles of operation. Further analysis of the capture experiments indicates that holes (h+) and superoxide radicals (·O2⁻) are the primary active species responsible for RhB degradation. This study not only provides new insights into the design of high-efficiency photoelectrode, but also offers new solutions for environmental pollution control.