Electrochemical Anodization Research Articles

Structural and Hydrophilic Properties of Nanoporous Aluminium Oxide Film as a Function of Voltage Anodization

Abstract The impact of voltage on the formation of nanopores through electrochemical anodization of high-purity aluminum was examined. The electrochemical bath was carefully prepared with oxalic acid electrolyte, while a 99.5% pure aluminum electrode served as the cathode and an aluminum template as the anode. The anodization process was conducted at room temperature, with voltage increments ranging from 20V to 65V, which was made possible by the in-house electrochemical cell. Notably, each incremental increase in voltage yielded a significant surge in current density, accompanied by a marked expansion in nanopore size, growing from approximately 35 nm to 125 nm. X-ray diffractometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Rutherford backscattering spectrometry were used to characterize the films. A slight phase change was observed in the aluminum substrate's FCC structure after the anodization process, transitioning to a monoclinic structure at 39° and 45° for all applied potentials. The stoichiometry of the films was determined through RBS analysis. The nano pores' resulting morphology and phase composition were further examined using SEM and EDS, providing insights into their structural characteristics. Furthermore, the water contact angle of the anodized aluminum oxide samples was measured, revealing a range of approximately 85.16 to 61.01 degrees.

Synthesis and Characterization of TiO2 Nanotubes for High-Performance Gas Sensor Applications

In this study, we investigated the fabrication, properties, and sensing applications of TiO2 nanotubes. A pure titanium metal sheet was used to demonstrate how titanium dioxide nanotubes can be used for gas-sensing applications through the electrochemical anodization method. Subsequently, X-ray diffraction indicated the crystallization of the titanium dioxide layer. Scanning electron microscopy and transmission electron microscopy then revealed the average diameter of the TiO2 nanotubes to be approximately 100 nm, with tube lengths ranging between 3 and 9 µm and the thickness of the nanotube walls being about 25 nm. This type of TiO2 nanotube was found to be suitable for NO2 gas sensor applications. With an oxidation time of 15 min, its detection of NO2 gas showed a good result at 250 °C, especially when exposed to a NO2 gas flow of 100 ppm, where a maximum NO2 gas response of 96% was obtained. The NO2 sensors based on the TiO2 nanotube arrays all exhibited a high level of stability, good reproducibility, and high sensitivity.

Study on electrochemical anodization initiation and progression of binderless tungsten carbide (WC) through experimentation and simulation

This article explores the electrochemical anodization of binderless tungsten carbide (WC) using computational simulations and experimental methods. It aims to comprehend the complex relationship between anodization time, surface roughness, elemental composition, and current behavior on polished and non-polished substrates. COMSOL Multiphysics models provide the initial findings by meticulously mapping the electrolyte's potential and the current density vectors. These simulations reveal the fundamental electrochemical behaviors anticipated during anodization, particularly emphasizing the regions near the anode expected to undergo anodization. Experimental observations confirm the simulation results, showcasing how non-polished WC surfaces, replete with inherent imperfections, undergo anodization characterized by fluctuating current densities and compositional changes, highlighting the profound influence of surface defects on electrochemical processes. On the other hand, when WC substrates are polished, they show a more consistent and controlled anodization process. This suggests a close connection between the occurrence of anodization and the surface treatment, ultimately influencing the effectiveness of anodization. This comprehensive study, which combines simulation and experimentation, greatly enhances the understanding of the electrochemical anodization of WC. It suggests potential methods for enhancing surface modifications to expand the range of applications for WC, particularly in precision glass molding, aerospace, and medical industries.

Anodized SLM Ti6Al4V surfaces: influence of surface characteristics on NTs growth and resulted surfaces properties.

TiO2 nanotubes (NTs) obtained via electrochemical anodization (EA) on conventionally machined titanium surfaces are reported to be promising for achieving mucointegration in dental implant therapy. Dental abutments, manufactured by selective laser melting (SLM), combined with thermal post-treatment, present a promising alternative to conventionally machined titanium. Based on an original protocol, this study aims to investigate how the characteristic microstructure of the α + β phases in post-heated SLM Ti6Al4V can influence the growth of NTs and the resulting physical and chemical surface properties. Ti6Al4V-SLM discs were fabricated, heat post-treated and mechanically polished. The samples were then subjected to EA under different voltage conditions (10, 20 and 30 V). The specimens' surfaces were characterized at the same location, before NTs formation by electron backscatter diffraction (EBSD), and after by scanning electron microscopy (SEM). Then, roughness and wettability were studied to determine how EA affects surface properties compared to conventionally machined and polished titanium surfaces without NTs (reference). Surface reactivity was evaluated through chemical analysis and collagen binding capacities. The self-organized TiO2 layer was developed on the α phase only and the β phase was preferentially dissolved. The characteristic dimensions of the nanotubes (diameter, length and wall thickness), measured by SEM image analysis, increased proportionally with the rise in voltage but were not affected by the crystallographic orientation of the underlying α grain. Micro-roughness was the same for nanotubular and reference surfaces. Wettability was improved, as was surface reactivity towards collagen, which may contribute to improved bioactivity of titanium surfaces in dentistry.

A Study on Cu Decorated Anodic TiO2 Nanotubes for Non-Enzymatic Glucose Sensing and Photoelectrochemical Water Splitting Application

Free-standing, surface-modified TiO2 nanotubes(TNTs) decorated with copper nanostructures have been extensively studied as promising materials for their application in biosensing and photo-electrochemical splitting of water. Here, the TNTs are prepared by electrochemical anodization followed by modification with copper nanostructures via UV-assisted photo-reduction technique. Field-emission scanning electron microscopy and X-ray diffraction studies confirmed the structural and morphological properties of the TNTs, along with their tubular architecture and mixed-phase composition of Anatase-Rutile. Energy-dispersive spectroscopic analysis verified the successful deposition of copper. Diffuse reflectance spectroscopy revealed an electronic band gap of 3.2 eV. The copper-modified TNTs showed an enhanced sensitivity in the sensing of glucose to the tune of 0.52 mA mM−1 cm−2 with a high linear range of 0.5 to 7 mM and showed superior selectivity against interferents. It was found that the modified TNTs exhibited a higher photocurrent response of 1.09 mA cm−2 compared with pristine TNTs (0.69 mA cm−2). These findings indicate the promising potential of copper-modified TNTs for continuous glucose monitoring and photo-electrochemical applications.

On the Optimization of Roughness and Corrosion Resistance of Laser Beam Powder Bed Fusion Fabricated Ti–6Al–4V Parts—An Electrochemical Approach

Laser beam powder bed fusion is emerging as a technology for fabricating components made of advanced alloys, such as Ti–6Al–4V. However, it suffers from rough as‐built (AB) surfaces, necessitating postprocessing for desired quality and performance. Electrochemical methods such as electrochemical polishing (ECP) and anodization (AN) are promising postprocessing methods; ECP can effectively smoothen surfaces irrespective of their complexity and hardness, while AN enhances the material's corrosion resistance. However, literature lacks research that discusses combined ECP and AN treatment on surface texture evaluation and corrosion behavior. This work presents a detailed study on the effects of different processing factor levels using a Taguchi design of experiment (DOE) approach and discusses the underlying process mechanisms. The optimized treatment conditions to achieve highest roughness improvement and best corrosion resistance are discussed and the most influential postprocessing factors are revealed and ranked. The treatment that achieved smooth surfaces and high corrosion resistance is ECP at 20 V and 15 °C for 20 min, followed by AN at 15 V for 5 min. This treatment achieves a 72% roughness improvement, providing an arithmetic areal surface roughness of 2.63 μm and a corrosion current density of 0.09 μA cm−2, which is almost similar to the AB part.

Advancing wastewater treatment: The efficacy of carbon-based electrochemical platforms in removal of pharmaceuticals

The study addresses the efficiency of innovative biochar- and g-C3N4-coated electrochemical platforms in removing selected pharmaceuticals and their metabolites from wastewater, with a focus on cost-effective and scalable materials. Analysis of effluent from the wastewater treatment plant revealed significant concentrations of 25 pharmaceuticals, highlighting the plant’s limited treatment efficacy. Notably higher levels of Telmisartan, Tramadol, and Diclofenac were found. The novelty of this work lies in the use of biochar- and g-C3N4-coated Raschig rings and glass beads as efficient electrochemical anodes offering high degradation capabilities. Adsorption-only tests (without voltage load) confirmed that no significant pharmaceutical removal occurs without electrochemical activation, highlighting the importance of electrochemical degradation. For the first time, we observed the formation of hydroxyl radicals (•OH) and singlet oxygen (1O2) during the electrochemical degradation process using g-C3N4-coated anodes, significantly enhancing degradation efficiency. The biochar-coated Raschig rings achieved over 80 % removal efficiency for all tested pharmaceuticals, with a power consumption of 85.2 kWh/m3. In comparison, biochar-coated beads exhibited a removal efficiency ranging from 9 % to 99 %, consuming 75 kWh/m3, while g-C3N4-coated rings showed the lowest performance at an energy consumption of 45 kWh/m3. These findings demonstrate the potential of both, biochar- and g-C3N4-based electrochemical platforms as a viable, scalable solution for advanced wastewater treatment, particularly for pharmaceutical degradation.

Electrodeposited ZnO Nanostructures on ITO Surfaces: Exploring Their Efficacy for Cholesterol Biosensing Applications

In this study, ZnO nanostructures were prepared by electrochemical anodization of electrodeposited Zn on ITO/glass substrates for cholesterol detection. The efficiency of the developed ZnO nanostructures in the detection of the Cholesterol oxidase (ChOx) enzyme was determined by the cyclic voltammetry method. The XRD and SEM results confirmed the synthesis of ZnO nanostructures prepared by the anodization method with various parameters. The effect of electrodeposition and anodization time on the morphology was observed. Cyclic voltammetry of ZnO/Zn/ITO/glass and Pt/ZnO/Zn/ITO/glass electrodes in electrolytes with various cholesterol concentrations was performed. The detection limit of the obtained Pt/ZnO/Zn/ITO/glass structured electrode was calculated as 0.965x10-3M. The resulting material with a layered structure may have potential applications in electrochemical sensors and biosensors in biomedical applications. In addition to biosensing performance, this study proposes a new approach for the development of ZnO-based biosensors that does not require expensive infrastructure and raw material costs, making it possible to develop high-sensitivity biosensor electrodes with lower detection limits with improvements to be made in future studies.

TiO2 nanotubes zeolite nanophotocatalyst performance efficacy toward the photocatalytic degradation of triclocarban in bathroom greywater

Triclocarban (TCC) is persistent in aquatic environments, where it can remain stable for extended periods. It can cause long-term exposure, potentially affecting ecosystems and human health through contaminated fish or water. Therefore, this study aims to investigate the degradation of TCC in bathroom greywater by the application of TiO2 nanotubes coated with zeolite (TNZPC) in photocatalytic degradation. Electrochemical anodization (ECA) and electrophoretic deposition (EPD) were applied to form TNZPC. Field Emission-Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), and X-ray Fluorescence (XRF) verified the characterization of TNZPC accordingly and the degradation kinetics of TCC followed the pseudo-first-order model of Hinshelwood. The highest degradation rate, reaching 95.2%, was observed at pH 11, while the lowest rate was at pH 3, with a degradation efficiency of only 72.6% after 60 minutes of irradiation with utilization of 0.75 cm2 of TNZPC. The mechanism study has verified eleven intermediate products were produced during TCC degradation by the process of oxidation, ozonation, hydroxyl radical (*OH), and dichlorination. The study suggests that finding the optimum conditions such as photocatalyst modification, cationic material, light sources, TCC initial concentration, pH, and TNZPC size play crucial roles in significant TCC photocatalytic degradation.

Electrochemical Engineering of Anode with Zincophilic Polymer Interface for Reversible Zinc Battery

AbstractAqueous rechargeable zinc‐ion batteries are emerging as green and safe energy devices owing to their high energy density and eco‐friendliness. The bottleneck is the inhomogeneous nucleation resulting in the growth of Zn dendrites and the parasitic side reactions at the anode. Herein, an electrochemical anode engineering strategy is demonstrated to curb the uncontrolled dendritic growth and side reactions. It involves the in situ generation of a solid‐electrolyte interface based on a Zn nanoparticle‐embedded poly(acrylic acid) hybrid layer (PAA‐nZn) on the anode. The homogeneously distributed polar functionalities and porous nature of the polymer regulate the uniform zinc ion flux, and the embedded zinc particle serves as nucleation sites for zinc plating. The hybrid layer reduces the nucleation overpotential and promotes instantaneous nucleation. The symmetrical cell made with PAA‐nZn@Zn has a lifecycle of >860 h with a voltage gap of 28 mV. The full cell fabricated by pairing the engineered anode with α‐MnO2 cathode showed a high discharge specific capacity of 238.3 mAh g−1 at 0.2 A g−1 with a capacity retention of 81.76% after 200 cycles and a long lifecycle. The electrochemical engineering of the anode suppresses the dendritic growth and protects the anode from unwanted side reactions and passivation.

Coupling between the photoactivity and CO2 adsorption on rapidly thermal hydrogenated vs. conventionally annealed copper oxides deposited on TiO2 nanotubes

AbstractHighly ordered spaced titanium dioxide nanotubes were fabricated via electrochemical anodization and modified with titania nanoparticles and copper oxides. Such materials were rapidly annealed in hydrogen atmosphere or conventionally in a tube furnace in air, in which the temperature slowly increases. Applied synthesis procedure can be considered as simple, cost-effective, and environmentally friendly as it allows for reduction in used materials and enhances sustainable engineering. Manipulating the chemical composition of materials by different thermal treatments resulted in various photoelectrochemical activities and density of CO2 adsorption sites. Rapidly annealed nanotubes decorated by copper oxides exhibit excellent electrochemical properties where one electrode combines both: solar to electricity conversion (photocurrent under visible light 30 µA/cm2) and CO2 adsorption systems (18 times higher current after CO2 saturation). Rapidly thermal hydrogenated TiO2 nanotubes with copper oxides had 17 times higher photocurrent and wider absorption band (380–780 nm) than conventionally annealed ones. Furthermore, the crystal planes such as Cu (111), Cu (220), Cu2O (110), CuO (002) and Cu0, Cu+, Cu2+ oxidation states, and oxygen vacancies were recognized for hydrogenated sample. It should be highlighted that thermal annealing conditions significantly affects ability of copper oxide to CO2 adsorption and CO2 reduction reaction for hydrogenated electrode. Graphical abstract

Inflammatory or Reparative? Tuning Macrophage Polarization Using Anodized Anisotropic Nanoporous Titanium Implant Surfaces

Modulating macrophage phenotype based on implant surface characteristics, including topography and chemistry, has been employed to enhance osseointegration and long‐term functional outcomes for titanium (Ti)‐based implants. An excessive and/or prolonged M1 macrophage response can lead to damaging immune‐inflammatory reactions, negatively influencing the fate of the implant, and hence, modulating these responses via nanoscale implant surface modification is an emerging paradigm. Herein, an anodized titanium implant surface based on single‐step electrochemical anodization, with preserved underlying microfeatures and superimposed nanopores (50 and 70 nm), compared with irregular rough and microrough (machined‐like) surfaces, is investigated for its effect on the functions of primary macrophages in vitro. Significantly reduced macrophage proliferation and increased tissue‐reparative M2 phenotype polarization are confirmed for the nanopores, which are more pronounced for 70 nm diameter. Moreover, osteoclastogenesis is reduced while osteogenic differentiation of osteoblasts is enhanced for the nanopores (higher for 70 nm pores). Advanced nanoengineered Ti implants can enhance titanium implant tissue integration by modulating the inflammatory response at the implant–cell interface.

Construction of 0D Ti3C2Tx MXene nanoparticles sensitized 1D TiO2 nanotube arrays for enhanced photocatalytic and photoelectrochemical properties

Developing efficient photocatalysts with highly active facets and appropriate cocatalyst hybridization to form heterostructure is a valid way to expedite the separation of photoexcited electron-hole pairs. Herein, a novel 0D/1D Ti3C2Tx MXene/TiO2 photocatalyst was fabricated for photoelectrochemical (PEC) water splitting and tetracycline antibiotic photocatalytic degradation. Meanwhile, highly-exposed TiO2 nanotube arrays were prepared by electrochemical anodizing method, and Ti3C2Tx nanoparticles with mixed terminal group were uniformly grown on the surface of TiO2 through the hydrothermal and solvothermal process, respectively. Compared with pure TiO2, the Ti3C2Tx/TiO2 heterostructure exhibited different degrees of enhancement in PEC and photocatalytic degradation activities under simulated sunlight. The TNT/M-h sample yielded a photocurrent density of 1.77 mA cm−2 at 0 V (vs. SCE) and achieved a 95.57 % photocatalytic removal rate of tetracycline within 140 min. The excellent performance originated from the strong interfacial contact and work function discrepancy between the ordered tubular structure of TiO2 and 0D Ti3C2Tx nanoparticles, which realized the high-efficiency photogeneration and transfer of electron-hole pairs.

Enhanced properties of TiO2 nanotubes through α-Fe2O3 surface decoration: Synthesis, characterization, and performance evaluation

Electrochemical anodization, under a constant voltage of 45 V and for 15, 30, and 45 min, was performed to fabricate highly ordered TiO2 nanotubes. Depending on the processing paramters, the diameter of the TiO2 nanotubes was found to be around 95 ± 6 nm, while the thickness of TNT layer exhibited a change with anodizing time, varying from 1 to 4 μm. Subsequent to the anodization α-Fe2O3/TiO2 heterogeneous structure was created by the spin coating of iron precursor based solutions on TiO2 nanotubes. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis were utilized to ascertain the phase structure and morphology of TiO2 nanotubes. The change of optical band gap values depending on the processing parameters was calculated using UV–Vis spectrophotometer data. The photocatalytic performances of the samples, namely the degradation rates and kinetics, were evaluated by examining the photodegradation of methylene blue (MB). The (TC15) sample, obtained by anodizing for 15 min and decorated with α-Fe2O3, exhibited the highest photocatalytic activity, with a degradation efficiency of 70 % at the end of 7 h of light exposure. On the other hand, the inhibition percentages of bacterial growth were examined and it was seen that the TC30 sample with the highest value was 88.89 % for E.coli bacteria and 70.57 % for S.aureus. To assess the mechanism of antimicrobial activity, ROS (Reactive Oxygen Species) Analysis were perfomed on T30 and TC30 groups and the ROS amount of TC30 was higher than T30. According to the results of the L929 mouse fibroblast cytotoxicity experiment with indirect contact according to ISO 10993-5 standards, all samples showed a successful performance in terms of cell viability. The cell viability of TC15 was higher in comparison to the control group.

Fabrication of arrayed V-shape micro-nano hierarchical structures for dew collection

Planer 2D nanopore arrays of porous anodic alumina can be unfolded to designed 3D arrayed micro-nano hierarchical structures by a programmed anisotropic electrochemical anodization, which consists of programed polymer masking and stepped anodization. Arrayed symmetrical and asymmetrical V-shape tiered micro grooves with nanotip-capped nanopore structures are respectively custom tailored to obtain high-efficiency dew collection. It is found that symmetrical V-shape tiered micro grooves with nanotip-capped nanopore structures show collection efficiency (36.176 ± 3.832 mg cm−2 h−1) twice as much as that of pure nanostructured surface, where the environment temperature is ∼18 °C, the relative humidity is ∼86 % and the sample temperature is ∼5 °C. Owning to the larger dew nucleation area, low solid-liquid adhesion and faster dew growth rate, the jumping micro-dews quickly gather and growth to big dews at the bottom of the V-shape tiers as the samples horizontally placed, which can easily fall off as turn the samples to vertical. Due to the simple equipment, low cost and large-area fabrication ability, these arrayed micro-nano hierarchical structures not only have potential to become high efficiency dew collector but also could be a platform for the controlled preparation of 3D complicated micro-nano structures of various materials with advanced functions.

(Invited) Novel Anodic Oxide Nanotube Array Architectures for Solar Photoelectrochemical Fuel Generation

Electrochemical anodization has progressed from its level as a low-cost commercial technique to fabricate corrosion and abrasion resistant compact oxide coatings to the status of an effective method for growing a variety of oxide nano-architectures, particularly nanorods, nanowires, nanotubes, nanoporous films, and nanoflowers. Among these structures, self-organized vertically aligned nanotubes of oxide semiconductors have been demonstrated to possess interesting electrical, optical and mechanical properties. As in the case of most low dimensional materials, these structures also possess high surface area. Nevertheless, their unique properties applicable to solar energy conversion processes such as photoelectrochemical (PEC) fuel generation arise primarily from their vertical orientation, their ability to keep the charge carriers always in the vicinity of the surface and the pathways they offer for facile charge transport. They can form heterostructures with other low dimensional materials and function synergistically to enhance the efficiency of the PEC processes. Anodic nanotube arrays of only a few oxide semiconductors have been discovered so far; however, expanding the list further has been proven difficult. Recently, we have developed a few novel nanotubular semiconductors promising for PEC fuel generation. This presentation provides the details of their fabrication process and performance as photocatalysts for solar fuel generation.

(Invited) Engineering of Nanostructured Aluminum-Based and Polymer-Based Platforms for SERS Sensing

There has been great hope for ultrasensitive detection methods with the application of Surface Enhanced Raman Spectroscopy (SERS) because of its impressive advancements. Nevertheless, a major challenge is the creation of large-scale, controllable, and reproducible substrates with high SERS activity [1]. As a basis for SERS detection, we report here the fabrication of different types of aluminum-based and polymer-based SERS platforms with the synthesis of gold nanoparticle (AuNP) arrays on them. The tunability of the AuNPs size and distribution is achieved by methodically controlling the aluminum substrates nanostructuration and the subsequent processes for the synthesis of the AuNP. This research presents a scalable and dependable approach for creating ordered Au patterns on nanostructured aluminum and polymer substrates.For both aluminum-based and polymer-based platforms, the initial formation of nanoporous anodic alumina (NAA) on an aluminum substrate by electrochemical anodization [2] is essential. The electrolytes used (sulphuric, oxalic, or phosphoric acid) and its respective concentration determines the ideal voltage for anodization and the electrolyte temperature [3,4]. The formed NAA layer is chemically removed obtaining a nanostructured aluminum substrate with a hexagonally ordered distribution of nanoconcavities [5,6]. The distance between nanocavities ranges from tens to hundreds of nanometers depending on the electrolyte used [7]. The polymer-based nanostructured substrates are formed with the deposition of the selected polymer on the obtained aluminum nanoconcavities substrates and peeled off when dried. Instead of nanoconcavities, it presents a distribution of nanosemispheres that corresponds to the imprinting of the aluminum nanoconcavities on the polymer.The final SERS platforms are obtained with the gold sputtering on the nanoconcavities aluminum substrates and the polymer substrates, followed by a thermal annealing process [8]. The result is a scalable, ordered and controlled distribution of AuNPs on the nanostructured substrates (Fig. 1). An evaluation of the sputtering time and the thermal annealing paramenters (time and temperature) is presented. Over a large surface area of several square centimeters, the AuNPs size, shape, and interparticle spacing may be controlled by using the flexible manufacturing method discussed in this work.All these AuNPs nanostructured platforms have shown high and interesting amplifications of the Raman signal demonstrating its suitability for SERS detection of several molecules like 4-Mercaptopyridine, rhodamine, streptavidine, melamine, etc. Acknowledgments This work was supported by the Spanish Ministerio de Ciencia e Innovación (MICINN/FEDER) PDI2021-128342OB-I00, by the Agency for Management of University and Research Grants (AGAUR) ref. 2021-SGR-00739 and by the Catalan Institution for Research and Advanced Studies (ICREA) under the ICREA Academia Award. Has also received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 945413. References Di Anibal, Carolina V., Lluís F. Marsal, M. Pilar Callao, and Itziar Ruisánchez. "Surface Enhanced Raman Spectroscopy (SERS) and multivariate analysis as a screening tool for detecting Sudan I dye in culinary spices." Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy87 (2012): 135-141.Macias, Gerard, Laura P. Hernández-Eguía, Josep Ferré-Borrull, Josep Pallares, and Lluís F. Marsal. "Gold-coated ordered nanoporous anodic alumina bilayers for future label-free interferometric biosensors." ACS applied materials & interfaces5, no. 16 (2013): 8093-8098.Kumeria, Tushar, Abel Santos, Mohammad Mahbubur Rahman, Josep Ferré-Borrull, Lluís F. Marsal, and Dusan Losic. "Advanced structural engineering of nanoporous photonic structures: Tailoring nanopore architecture to enhance sensing properties." Acs Photonics1, no. 12 (2014): 1298-1306.Santos, Abel, Josep M. Montero-Moreno, Julien Bachmann, Kornelius Nielsch, Pilar Formentín, Josep Ferré-Borrull, Josep Pallares, and Lluís F. Marsal. "Understanding pore rearrangement during mild to hard transition in bilayered porous anodic alumina membranes." ACS applied materials & interfaces3, no. 6 (2011): 1925-1932.Hernández-Eguía, Laura P., Josep Ferré-Borrull, Gerard Macias, Josep Pallarès, and Lluís F. Marsal. "Engineering optical properties of gold-coated nanoporous anodic alumina for biosensing." Nanoscale Research Letters9 (2014): 1-8.Palacios, R., P. Formentín, J. Ferré‐Borrull, J. Pallarés, and L. F. Marsal. "Polymer nanopillars using self‐ordered nanoporous alumina templates." physica status solidi c6, no. 7 (2009): 1584-1586.Vojkuvka, Lukas, Lluís F. Marsal, Josep Ferré-Borrull, Trifon Trifonov, and Josep Pallarés. "Fabrication of self-ordered nanoporous alumina for optical and structural characterization." Contributions to science4, no. 2 (2008): 219-222.Dar, Gohar Ijaz, Elisabet Xifre‐Perez, and Lluis F. Marsal. "Fabrication of Au‐Decorated Al Nanoconcavities Platform for Augmented SERS." Advanced Materials Interfaces(2023): 2300560. Figure 1

Totally Tubular TiO2 Nanotubes as Semiconducting Material for Dye-Sensitized Photoelectrodes

The use of chemical bonds to store solar energy is a promising approach to address the intermittency of the sun by harnessing sunlight to drive chemical transformations. One strategy to drive these processes is to use a bespoke semiconductor surface implemented in a photoelectrode to absorb light and generate charge carriers that can drive redox reactions such as the direct oxidation of adsorbed species on the photoanode. To minimize recombination of photogenerated electron-hole pairs, molecular donor-chromophore-acceptor (D-C-A) systems can be used to sensitize wide bandgap semiconductors for visible light absorption and to generate (high energy) long-living charge separated states. Such assemblies represent a photoelectrode for dye-sensitized photoelectrochemical cells (DS-PECs). Presented here are recent findings using molecularly sensitized TiO2 nanotubes as a nanohybrid architecture for DS-PECs. The highly ordered and oriented 1D-nanostructures are purpose-grown using a self-organizing electrochemical anodization approach. The nanotube mouth is functionalized with a Cu(I)-based donor-chromophore-acceptor system by direct assembly at the surface. The resulting photoanodes are investigated against different water oxidation catalysts (e.g., [Cp*Ir(pyalk)OH], pyalk = 2-(pyridine-2-yl)propan-2-ol; CoOx) for their ability to generate oxidizing equivalents that can subsequently drive follow-on oxidation reactions. A more common TiO2 nanostructure morphology (e.g., nanospheres) and simpler Cu(I)-based chromophores are also examined for comparative purposes to highlight the advantages of the proposed assembly.It is well understood that the role of the semiconductor is to connect the molecular components and transfer/store charge carriers from the excited dye to drive redox processes. The TiO2 nanotubes used here are synthesized by self-organized electrochemical anodization (SOA); a process Involving an anode/cathode arrangement where Ti is used as the anode. This process is a balance between the electrochemical formation of TiO2 and simultaneous chemical dissolution in fluoride-containing electrolytes. The resulting semiconducting film is found to be a vertically oriented, size-controlled, and back-contacted nanostructured array of TiO2 on a foil of titanium. In addition to this composition inheriting high chemical stability, the morphology can grant added benefits such as two-dimensional confinement, directional charge transport and orthogonal charge separation.[1]A crucial limiting factor for the performance of this system is the recombination of the electron-hole pairs. By using a transition metal complex or chromophore (C) that is covalently linked with electron donating (D) and electron accepting (A) moieties, the energy levels can be aligned for charge-transfer processes between the electroactive groups for directional electron transport and formation of a charge-separated state.[2] Copper(I) D-C-A assemblies are also of interest when taking into consideration the low-cost and photophysical properties when compared to typical ruthenium(II) polypyridine chromophores used in these types of cells. Transient photocurrent measurements of the photoelectrode suggest that the TiO2 nanotubes’ mouths generate a base photocurrent, which could be associated with graphitic-like carbon impurities extending light absorption for photoactivity. Furthermore, once the surface is decorated with the copper(I) D-C-A assembly, the photocurrent is significantly increased, enabling light-driven oxidation of CoOx photoelectrochemically deposited on the surface of the photoelectrode.REFERENCES[1] Nguyen, N. T.; Altomare, M.; Yoo, J. E.; Taccardi, N.; Schmuki, P. Noble Metals on Anodic TiO2 Nanotube Mouths: Thermal Dewetting of Minimal Pt Co-Catalyst Loading Leads to Significantly Enhanced Photocatalytic H2 Generation. Adv. Energy Mater. 2016, 6, 1501926. DOI: 10.1002/aenm.201501926[2] Singh, Z.; Kamal, S.; Majewski, M. B. Copper(I) Donor−Chromophore−Acceptor Assembly for Light-Driven Oxidation on a Zinc Oxide Nanowire Electrode. J. Phys. Chem. C. 2022, 126, 39, 16732-16743. DOI: 10.1021/acs.jpcc.2c04652 Figure 1

Research on solar cell preparation technology for cutting-edge technology

Flexible dye-sensitized solar cells are highly valued as a practical technology with low production costs. In this paper, we study flexible dye-sensitized solar cells consisting of nanocrystalline TiO2 thin-film electrodes based on titanium metal and counter electrodes based on conductive coated polymers. In order to improve the photoelectric conversion efficiency, nanocrystalline TiO2 film electrodes and TiO2 nanotube film electrodes based on titanium metal and TiO2 nanotube film electrodes are prepared by DC low-field electrophoretic deposition, electrochemical anodizing and screen printing under DC and pulse voltages combined with high-temperature sintering methods; and platinum-carrying counter electrodes and carbon counter electrodes based on conductive coated polymers are prepared by low-temperature techniques, such as constant-current electrochemical deposition and chemical reduction. The mechanisms and characteristics of different preparation methods and optimization techniques are analyzed and discussed, and the performances of nanocrystalline TiO2 thin film electrodes and counter electrodes prepared by different methods are compared. On this basis, the all-flexible solar cell is developed, and the maximum photoelectric conversion efficiency reaches 6.74%.

Cobalt-doped TiO2 by one-step anodization and with a HCl-based solution for the study of hardness and adherence

TiO2 was doped with cobalt through electrochemical anodizing and the use of HCl as the base solution. EDS corroborated the presence of cobalt in the anodized film with an atomic percentage of 0.26 %. FE-SEM revealed the formation of collapsed and/or deformed TiO2 nanotubes. Diffraction patterns revealed the presence of anatase and rutile after treatment, with compressive stresses by cobalt. The Vickers microhardness increased with respect to temperature until reaching a maximum value of 9.27 GPa. Using Microscratch it was possible to observe how ductility, crystalline structure, and thickness have a considerable effect on the critical loads, the depth of the scratches, and the quality of the adhesion of the films.