Applications In Photoelectrochemistry Research Articles

Engineering intrinsic defects in CuO NWs through laser irradiation: Oxygen vs copper vacancies

Defect engineering in CuO nanomaterials has been extensively investigated because this technology can greatly improve the performance of CuO components in a variety of applications. While many previous studies have focused on the role of oxygen vacancies, (VO), in CuO, little attention has been paid to that of copper vacancy centers, (VCu), since the presence of these defects is often difficult to quantify. As a result, the specific roles played by these different vacancy centers on the measured properties of CuO have not been studied systematically. In this article, we show that the concentration of both VO and VCu centers can be engineered in CuO NWs through nanosecond (ns) laser irradiation. The identification of these vacancies was achieved through X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Absorption spectra and diffuse reflectance spectra of laser-processed samples show that increasing the concentration of VO centers enhances the optical absorption of CuO in the visible region. Data obtained from Mott-Schottky and Nyquist plots, together with measured I-V characteristics, show that laser-induced VCu centers can enhance the carrier concentration in CuO NWs. These data, in addition to O 1s XPS spectra on laser-processed and unprocessed samples as well as cyclic voltammetry, also indicate that laser irradiation can significantly enhance surface adsorption for applications in photo-electrochemistry and electrochemistry. To demonstrate the efficacy of this laser irradiation technique for potential electrochemistry applications, the role of laser-induced VCu and VO defect centers in CuO NWs on the non-enzymatic sensing of glucose has also been investigated. We find that the introduction of VO centers in CuO NWs enhances the current response for glucose sensing while the presence of VCu centers inhibits this response.

Cu2−xSe/FeSe2 Z-type heterojunction demonstrate versatile boosting photoelectrochemical, electrocatalytic and photocatalytic properties

A multi valence state Cu2−xSe/FeSe2 (CFS) Z-type heterojunction catalyst was constructed by hydrothermal synthesis of 0D Cu2−xSe nanoparticles supported on 1D FeSe2 nanorods. In the catalysts, the Cu2−xSe shows multi valence as Cu2+ and Cu+ as well as FeSe2 had two valence states: Fe2+ and Fe3+. This multivalent state is conducive to electron transport, will reduce its resistivity, and change among different valence states in electrochemical reactions, resulting in improve its photoelectrochemical and electrocatalytic performance. Moreover, this Z-type heterojunction catalyst exhibited good oxidation and reduction ability which reveals the appropriate 0D/1D structure improves the carrier transport. That has been confirmed by photoelectrochemical, electrocatalytic and photocatalytic tests. Under the optimal composited ratio, the degradation rate (k) and photocurrent density of the heterojunction photocatalyst were 1.35 and 3.65 times higher than those of Cu2−xSe, respectively. The detected superoxide radical (O2-•) could prove the formation of Z-type heterojunction. This work provides a new strategy for developing a multifunctional boosted catalyst and reveals their promising applications in photoelectrochemistry, electrocatalysis, and photocatalysis.

Effect of Titanium Matrix Structure on Growth Morphology of Anodized TiO2 Nanotube Arrays for Applications in Photoelectrochemical Performances

In the application of a solar cell and photocatalytic system, anodized titanium dioxide nanotube arrays (TNTs) have one-dimensional highly ordered nanotube structure, so they have attracted much attention. In order to form ordered TNTs, many factors, such as voltage, anodizing time, solvent type, and so on, need to be controlled. However, these factors have mainly focused on the effect of external conditions, while the effect of internal factors such as the crystal structure of the titanium substrate on the growth of nanotubes have been less investigated. In this paper, the titanium substrate tissue structure with a (002) preferred orientation was obtained by a rolling treatment. On this basis, TNTs with highly ordered structure were constructed, and the effect of the titanium substrate structure on the nanotube growth morphology was investigated. The changes in morphology were characterized by scanning electron microscopy, and the relationship between the changes in the crystal structure and morphology of TNTs was systematically analyzed by combining metallographic structure and X-ray diffraction data. The changes in the electrochemical behavior of the titanium substrates after rolling were examined through electrochemical methods. The above results show that there are a large number of dislocations and microscopic internal stresses in the grain structure of the titanium substrate after rolling, which leads to improvement of the corrosion resistance of the materials. The changes in the microstructure of these materials make the nanotube arrays have highly ordered structure and better photoelectrochemical properties, which provides an idea for improving their applications in photoelectrochemistry.

Mind the Interface Gap: Exposing Hidden Interface Defects at the Epitaxial Heterostructure between CuO and Cu2O.

Well designed and optimized epitaxial heterostructures lie at the foundation of materials development for photovoltaic, photocatalytic, and photoelectrochemistry applications. Heterostructure materials offer tunable control over charge separation and transport at the same time preventing recombination of photogenerated excitations at the interface. Thus, it is of paramount importance that a detailed understanding is developed as the basis for further optimization strategies and design. Oxides of copper are nontoxic, low cost, abundant materials with a straightforward and stable manufacturing process. However, in individual applications, they suffer from inefficient charge transport of photogenerated carriers. Hence, in this work, we investigate the role of the interface between epitaxially aligned CuO and Cu2O to explore the potential benefits of such an architecture for more efficient electron and hole transfer. The CuO/Cu2O heterojunction nature, stability, bonding mechanism, interface dipole, electronic structure, and band bending were rationalized using hybrid density functional theory calculations. New electronic states are identified at the interface itself, which are originating neither from lattice mismatch nor strained Cu-O bonds. They form as a result of a change in coordination environment of CuO surface Cu2+ cations and an electron transfer across the interface Cu1+-O bond. The first process creates occupied defect-like electronic states above the valence band, while the second leaves hole states below the conduction band. These are constitutional to the interface and are highly likely to contribute to recombination effects competing with the improved charged separation from the suitable band bending and alignment and thus would limit the expected output photocurrent and photovoltage. Finally, a favorable effect of interstitial oxygen defects has been shown to allow for band gap tunability at the interface but only to the point of the integral geometrical contact limit of the heterostructure itself.

Novel 0D/2D Bi2WO6/MoSSe Z-scheme heterojunction for enhanced photocatalytic degradation and photoelectrochemical activity

The catalytic activity of a single catalyst could be optimized by constructing a Z-scheme heterojunction structure with another adaptive material. 0D Bi2WO6 nanoparticles exhibit good oxidation ability, while 2D MoSSe nanoplates with low internal resistance show excellent reduction ability. Herein, novel 0D/2D Bi2WO6/MoSSe Z-scheme heterojunction catalysts (BMSS) with different Mo: Bi molar ratios were developed by combining the advantages of pure Bi2WO6 and MoSSe. The matched energy bands may provide the possibility to construct heterojunction, and the internal electric fields could facilitate the separation and transmission of internal carriers. Energy band structure analyses and electron spin resonance (ESR) results have further confirmed the existence of the above Z-scheme heterojunction structure and internal electric field. More importantly, as-prepared BMSS catalysts were proved to have excellent oxidation and reduction ability from photocatalytic and photoelectrochemical results. With an optimized MoSSe loading ratio of 3.66%, the BMSS3 catalyst showed 4.13 times of photocurrent density than that of pure Bi2WO6 and displayed an excellent degradation rate (0.0377 min−1). It can be concluded that BMSS catalysts will have promising applications in photoelectrochemistry and photocatalysis.

Semiconducting eutectic materials for photocatalysis and photoelectrochemistry applications: a perspective.

The world of semiconductors has drastically improved human lifestyle due to its versatile applications. The demand for new efficient semiconductors is increasing day by day, giving birth to the idea of new synthesis methods. Here, the importance of semiconductor eutectic materials has been presented, as one of the potential candidates for solar-based devices such as photo-anodes for water splitting, along with the micro (μ) pulling method (as a synthesis method for semiconductor eutectic materials). A comparison of the efficiency of the present devices with the eutectic composites has been made, showing semiconductor eutectic materials as a better alternative. In addition, possible changes that can be achieved using the μ-pulling method to enhance the photo(electro)chemical (PEC) properties have focused on semiconducting eutectic materials in this article.

Enhanced electricity generation in photoelectrochemical cell using Sn-doped BiOCl photoanode

Photoanode material, due to its wide applications in photoelectrochemistry, has attracted much attention. In this work, tin-doped BiOCl (BiOCl-Sn) is prepared through a simple and effective method. A photoelectrochemical cell system with BiOCl-Sn as the photoanode is constructed. The short circuit current (Jsc) and open circuit voltage (Voc) are measured to be 0.0516 mA·cm−2 and 0.26 V. Both Mott–Schottky curve and valence band spectra prove that Sn doping leads to a shift of the conduction band minimum downward. Meanwhile, the results of photocurrent and impedance measurements reveal that the Sn doping accelerates the photocarriers separation. The photocatalytic redox properties of BiOCl-Sn are investigated by rhodamine B degradation and nitrogen fixation.

Tunable Photodetectors via In Situ Thermal Conversion of TiS3 to TiO2.

In two-dimensional materials research, oxidation is usually considered as a common source for the degradation of electronic and optoelectronic devices or even device failure. However, in some cases a controlled oxidation can open the possibility to widely tune the band structure of 2D materials. In particular, we demonstrate the controlled oxidation of titanium trisulfide (TiS3), a layered semicon-ductor that has attracted much attention recently thanks to its quasi-1D electronic and optoelectron-ic properties and its direct bandgap of 1.1 eV. Heating TiS3 in air above 300 °C gradually converts it into TiO2, a semiconductor with a wide bandgap of 3.2 eV with applications in photo-electrochemistry and catalysis. In this work, we investigate the controlled thermal oxidation of indi-vidual TiS3 nanoribbons and its influence on the optoelectronic properties of TiS3-based photodetec-tors. We observe a step-wise change in the cut-off wavelength from its pristine value ~1000 nm to 450 nm after subjecting the TiS3 devices to subsequent thermal treatment cycles. Ab-initio and many-body calculations confirm an increase in the bandgap of titanium oxysulfide (TiO2-xSx) when in-creasing the amount of oxygen and reducing the amount of sulfur.

Recent Progress and Development in Inorganic Halide Perovskite Quantum Dots for Photoelectrochemical Applications.

Inorganic halide perovskite quantum dots (IHPQDs) have recently emerged as a new class of optoelectronic nanomaterials that can outperform the existing hybrid organometallic halide perovskite (OHP), II-VI and III-V groups semiconductor nanocrystals, mainly due to their relatively high stability, excellent photophysical properties, and promising applications in wide-ranging and diverse fields. In particular, IHPQDs have attracted much recent attention in the field of photoelectrochemistry, with the potential to harness their superb optical and charge transport properties as well as spectacular characteristics of quantum confinement effect for opening up new opportunities in next-generation photoelectrochemical (PEC) systems. Over the past few years, numerous efforts have been made to design and prepare IHPQD-based materials for a wide range of applications in photoelectrochemistry, ranging from photocatalytic degradation, photocatalytic CO2 reduction and PEC sensing, to photovoltaic devices. In this review, the recent advances in the development of IHPQD-based materials are summarized from the standpoint of photoelectrochemistry. The prospects and further developments of IHPQDs in this exciting field are also discussed.

Improving photoelectric performance of MoS2 photoelectrodes by annealing

Semiconductor photoelectrochemistry (PEC) technology has attracted wide interest as it not only reveals the photoelectric properties of advanced materials, but also promotes energy conversion from the sunlight based on these materials. Herein, we investigated photoelectric properties of annealed and unannealed liquid phase exfoliated few-layer molybdenum disulfide (MoS2) photoelectrodes by PEC measurement. The linear sweep voltammograms and photoelectric response I-t curves demonstrate enhanced performance of MoS2 films after annealing. Nyquist impedance and Bode phase plots demonstrate a higher charge transfer property and a longer charge lifetime after annealing. The enhancement due to annealing could come from the increase of the crystalline and compact density of MoS2 nano-sheets, which is proved by X-ray diffraction and Raman spectroscopy in line with the absorption spectroscopy. Our results pave the way for the improvement of two-dimensional material based photoanodes for high performance of PEC applications by a simple method.

Photoelectrochemistry and sensor of NO based on a supramolecular system composed of polyhydroquinone and fullerene

An electron donor–acceptor linked supramolecular system composed of polyhydroquinone (PH2Q) and fullerene (C60) was prepared and characterized by different techniques like TEM, UV–vis, XRD and photoelectrochemical photocurrent detection techniques. The photoelectrochemical properties of nitric oxide (NO) were first investigated. An enhanced cathodic photocurrent response was obtained on the PH2Q-C60 modified ITO electrode under visible light radiation with NO as electron acceptor. The photoelectrochemical process of NO was discussed and a novel photoelectrochemical sensor of NO was developed. The influence of the main interferents, especially the significant interfering species NO2− was proved to be negligible. The photoelectrochemistry of NO and the new NO sensor may have potential applications in photoelectrochemistry and biological analysis field.

Extremely Thin Photoelectrode Architectures for Photocatalysis

Introduction Concepts from metamaterials, plasmonics and nanophotonics are highly promising to improve the design of future solar energy conversion devices. Here, I will describe how we use these concepts to design advanced photoelectrode architectures for driving two challenging photocatalytic reactions: water splitting and CO2 reduction. We focus on the light management aspect in extremely thin absorber structures and in plasmonic metal nanostructures, to achieve broadband omnidirectional solar light absorption while carefully choosing materials systems that allow for efficient charge separation and catalytic activity. Such thin-film absorber photoelectrodes hold promise for achieving enhanced charge carrier extraction, increased photovoltages, and the possibility to exploit hot carriers for purposes of driving chemical reactions. In addition, architectures made from two-dimensional materials building blocks allow us to tailor new electronic, catalytic and optical properties by engineering materials one layer at a time. However, light absorption in single-layer materials is generally small, and efficient photoconversion structures require nanophotonic concepts to enhance their optical properties. Experimental We are exploiting nanophotonics concepts to realize extreme light absorption in two-dimensional (2D) transition metal dichalcogenides. I will discuss the analytical models and three-dimensional electromagnetic simulations that we employ to engineer light absorption in these 2D materials and in plasmonic metal nanostructures, and describe our progress towards the experimental realization and characterization of such structures. Complementing these materials and device design efforts, we are developing an experimental characterization toolbox, including photoelectrochemical and spectroscopic techniques. Materials We have designed both plasmonic- and dielectric-based ultrathin photoelectrode structures 1. To create centimeter-scale nanostructured photoelectrodes, we have developed the synthesis of Anodic Aluminum Oxide (AAO) templates as generic deposition masks for plasmonic and non-plasmonic materials. The AAO masks can be transferred to a wide range of substrates (including rough transparent conducting oxides and metal oxides) and e-beam evaporation of metals of various sizes, shapes and periodicities can be accomplished. The AAO templates can also be used for lateral nanostructuring of two-dimensional materials. Sample characterization were performed by SEM, XRD, AFM. Photoelectrochemical measurements of water splitting were performed on plasmonic nanostructures, combined with suitable metal oxides for efficient charge separation. Results and Discussion Full-field electromagnetic simulations of our absorber structures suggest that they are suitable to substantially enhance the optical absorption over a broad wavelength range, covering regions of the solar spectrum that contain a large portion of the solar energy flux. The ultrathin nature of our structures also renders them relatively immune to efficiency reductions under non-normal incidence illumination. We will discuss first results on photoelectrode fabrication, and their materials-, optical and photoelectrochemical characterization. Conclusions This work is aimed at developing and characterizing advanced photoelectrode architectures for two challenging photocatalytic reactions, water splitting and CO2 reduction. Such structures will ultimately allow the deployment of solar-based approaches for driving large-scale applications in photoelectrochemistry and photocatalysis, and may hold promise for new generations of opto-electronic devices.

Mesoporous CdS-sensitized TiO2 nanoparticle assemblies with enhanced photocatalytic properties: Selective aerobic oxidation of benzyl alcohols

Mesoporous TiO2-based semiconductors with visible-light response are promising materials for photocatalytic and photoelectrochemistry applications. In this work, we have used surfactant-assisted aggregating assembly of CdS and TiO2 nanocrystals to assemble mesoporous binary CdS-TiO2 heterostructure. The product features a three-dimensional network of interconnected CdS quantum dots and anatase TiO2 nanoparticles and exhibits large internal BET surface area (157m2g−1) and uniform pores (ca. 7.5nm). Catalytic experiments showed an exceptionally high catalytic activity of these mesophases under UV–visible light oxidation of various para-substituted aryl alcohols, using molecular oxygen as oxidant. Moreover, product analysis and kinetic results indicated that these photooxidation reactions proceed via an electron transfer route from alcohol substrate to the excited states of the catalyst.

Preparation, characterization and photoelectrochemical property of ultrathin MoS2 nanosheets via hydrothermal intercalation and exfoliation route

A simple but effective hydrothermal intercalation and exfoliation route is developed to prepare ultrathin MoS2 nanosheets in high yield. The morphologies and microstructures of as prepared products are characterized by X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy and atomic force microscopy. It is found that zerovalent lithium is readily intercalated between the layers of MoS2 using ethylene glycol as both reductant and solvent in hydrothermal process. Subsequently ultrathin MoS2 nanosheets with good quality are obtained by the removing of lithium via the exfoliating process in water. The obtained ultrathin MoS2 nanosheets exhibit preferable photoelectrochemical and photoresponse activity under the illumination of simulated sunlight compared to bulk MoS2. Our results indicate that ultrathin MoS2 nanosheets have promising applications in photo-electrochemistry, heterogeneous catalysis, sensors and optoelectronic nanodevices.

Graphene and its derivatives for the development of solar cells, photoelectrochemical, and photocatalytic applications

Due to its unique atom-thick 2D structure and remarkable physicochemical properties, graphene has been making a profound impact in many areas of science and technology. In particular, a great deal of recent attention has been attracted to explore graphene and its derivatives for photoelectrochemical applications, with the potential to harness graphene's excellent properties for opening up new opportunities in next generation photoelectrochemical systems. Over the past few years, much work has been done in the design and preparation of novel graphene-based materials for a wide range of applications in photoelectrochemistry, ranging from photoelectrochemical solar cells, photocatalytic decomposition of organic pollutants, photocatalytic splitting of H2O, photocatalytic conversion for fuels, and so on. In this review article, we summarize the state of research on graphene-based materials from the standpoint of photoelectrochemistry. The prospects and further developments in this exciting field of graphene-based materials are also discussed.

Increasing the Open-Circuit Voltage of Photoprotein-Based Photoelectrochemical Cells by Manipulation of the Vacuum Potential of the Electrolytes

The innately highly efficient light-powered separation of charge that underpins natural photosynthesis can be exploited for applications in photoelectrochemistry by coupling nanoscale protein photoreaction centers to man-made electrodes. Planar photoelectrochemical cells employing purple bacterial reaction centers have been constructed that produce a direct current under continuous illumination and an alternating current in response to discontinuous illumination. The present work explored the basis of the open-circuit voltage (V(OC)) produced by such cells with reaction center/antenna (RC-LH1) proteins as the photovoltaic component. It was established that an up to ~30-fold increase in V(OC) could be achieved by simple manipulation of the electrolyte connecting the protein to the counter electrode, with an approximately linear relationship being observed between the vacuum potential of the electrolyte and the resulting V(OC). We conclude that the V(OC) of such a cell is dependent on the potential difference between the electrolyte and the photo-oxidized bacteriochlorophylls in the reaction center. The steady-state short-circuit current (J(SC)) obtained under continuous illumination also varied with different electrolytes by a factor of ~6-fold. The findings demonstrate a simple way to boost the voltage output of such protein-based cells into the hundreds of millivolts range typical of dye-sensitized and polymer-blend solar cells, while maintaining or improving the J(SC). Possible strategies for further increasing the V(OC) of such protein-based photoelectrochemical cells through protein engineering are discussed.

Epitaxial Growth of α-Fe<sub>2</sub>O<sub>3</sub> Thin Films on <i>c</i>-Plane Sapphire Substrate by Hydrothermal Method

Thin films of hematite find extensive applications in photoelectrochemistry, photocatalysis, and gas sensors. c-axis oriented hematite films have been directly grown on c-plane sapphire substrate using chemical method via hydrolysis of ferric cations. X-ray diffraction (XRD) reveals that the crystalline phases of the films and corresponding sediment produced in the solution were α-Fe2O3 and pure β-FeOOH, demonstrating the promotion of nucleation of hematite on sapphire substrate as a result of lowered interface energy. Phi-scan results indicate that the hematite films are grown with (0001) planes parallel to c-plane of Al2O3. Scanning electron microscopic observation shows that the hematite films are composed of pyramid-shaped nanocrystals with smooth surface facets.

Application of Photoelectrochemistry and Impedance Measurements to the Study of Passive Films on AlSl 304 Stainless Steel

Application of Photoelectrochemistry and Impedance Measurements to the Study of Passive Films on AlSl 304 Stainless Steel

ChemInform Abstract: Photoelectrochemical Studies of Passive Films

AbstractReview: (90 refs.

Interfaces between electronically and ionically conducting polymers: Applications to ultra high-vacuum electrochemistry and photoelectrochemistry

Interfaces between ionically conducting polymers as solid electrolytes and electronically conducting polymers as electrode materials are discussed both from the point of view of fundamental materials studies and the device potential of the structures. A new technique has been developed that allows both electrochemical synthesis and reduction/oxidation of conducting polymers in situ in ultra-high vacuum using thin-film polymer solid electrolytes, concurrent with the application of photoelectron spectroscopy techniques. Interfaces between thin-film polymer electrolytes and conducting polypyrole are also shown to have potential applications in photoelectrochemistry.