PEC System Research Articles

Modelling and experimental study on pipeline defect characterisations using a pulsed eddy current measurement

ABSTRACT Pipelines are widely used as the main transportation method in petrochemical and metallurgical industries. However, the special nature of the materials transported in pipelines means they are often subjected to high temperature, high pressure and corrosive conditions. This can lead to defects, such as thinning and cracking, resulting in pipeline failure and causing serious economic losses. Therefore, regular non-destructive testing of pipelines is particularly important. This paper uses the non-destructive testing method with pulsed eddy current technology to characterise pipeline thinning and defects. A preliminary study is conducted on the pulsed eddy current detection signal patterns for pipeline crack defects with varying orientations and quantities. A more portable pulsed eddy current detection device with an extended wall thickness detection range is developed. It can achieve measurements with a maximum thickness of 30 mm for detections of pipelines with rectangular defects and thickness-stepped reduced. The experimental results are consistent with modelling results, and the accuracy for pipelines with insulation layer is also investigated. On-site measurements using the PEC system are conducted on equipment sections with pipe thickness within 20 mm in a petrochemical plant. It is confirmed that the developed PEC inspection device can accurately characterises the thickness of pipelines with 0–50 mm cladding.

Degradation of tetracycline hydrochloride through g-C3N4/TiO2 nanotube arrays for photoelectrocatalytic activation of PMS system: Performance and mechanistic analysis

To enhance the pollutant degradation ability of TiO2 nanotube arrays (TNAs) in a photoelectrocatalytic system (PEC), g-C3N4/TNAs photoanode was synthesized using anodic oxidation-slow evaporation method. Then, peroxymonosulfate (PMS) was incorporated and the resulting PEC-PMS system was applied to degrade tetracycline hydrochloride (TCH). The results from SEM, XRD and UV–vis DRS analyses indicated that g-C3N4 was successfully loaded onto the surface of TNAs, reducing the forbidden bandwidth from 3.10 eV to 2.89 eV. I-t and EIS curves demonstrated that the loading of g-C3N4 increased the electron transfer rate of TNAs. The photoanode prepared with a g-C3N4 solution (concentration of 100 mg L−1) exhibited the best degradation performance for TCH. The degradation rate of TCH by the PEC-PMS system reached 95.69 % at a TCH concentration of 10 mg L−1, pH of 9, PMS dosage of 2 mM, and voltage of 2 V, significantly higher than that of the PEC system without PMS (35.14 %). The contribution of active radicals to the system was in the order of SO4·- > h+ > ·O2- > ·OH. Three possible pathways for TCH degradation were proposed based on the experimental results. In conclusion, this work provides a theoretical basis for the preparation of photoelectrodes responsive to visible light and their application in the degradation of pollutants by the PEC-PMS system.

Novel dual-photoelectrode Z-scheme PEC system for efficient TBBPA removal and debromination: Performance and promoting mechanism

Herein, a novel dual-photoelectrode Z-scheme photoelectrocatalytic system is created to achieve efficient synergistic anodic oxidation and cathodic reduction for TBBPA degradation and debromination. Based on the polydopamine-modified N-doped TiO2 nanotubes (PN-TNTs) photoanode and polydopamine-modified Cu2O nanowires (PC-CNWs) photocathode, the degradation, debromination and mineralization were 99.4%, 77.7% and 52.1% at 0.7 V under visible light for 2 h. The introduction of PDA enhances the visible light absorption by the TiO2 photoanode and protects the Cu2O photocathode from photocorrosion. The main active species identified by electron paramagnetic resonance (EPR) and scavenger experiments as •OH and e− were found to promote the degradation and debromination of TBBPA by oxidation and reduction, respectively. The degradation pathway of TBBPA was determined by Density Functional Theory (DFT) calculations and HPLC-MS analyses. Comparing the intermediates of single and dual chambers, it demonstrated that the photocathode was able to achieve the continuous debromination of TBBPA and intermediates, which reduced the toxicity. Finally, the stability, reusability and energy consumption were evaluated, confirming the feasibility of the system.

Customized Photoelectrochemical C−N and C−P Bond Formation Enabled by Tailored Deposition on Photoanodes

AbstractPhotoelectrochemistry (PEC) is burgeoning as an innovative solution to organic synthesis. However, the current PEC systems suffer from limited reaction types and unsatisfactory performances. Herein, we employ efficient BiVO4 photoanodes with tailored deposition layers for customizing two PEC approaches toward C−N and C−P bond formation. Our process proceeds under mild reaction conditions, deploying easily available substrates and ultra‐low potentials. Beyond photocatalysis and electrocatalysis, customized PEC offers high efficiency, good functional group tolerance, and substantial applicability for decorating drug molecules, highlighting its promising potential to enrich the synthetic toolbox for broader organic chemistry of practical applications.

H2O2-assisted photo-electrocatalytic and photocatalytic degradation of methyl violet by CuO-modified TiO2 nanotube arrays

Photoelectrocatalytic degradation is an environmental friendly and efficient technique providing solutions for the dire issue of water pollution. TiO2 nanotubes are widely used as the photocatalyst but its efficiency is restricted by the wide band gap. This study deals with the fabrication of CuO-modified TiO2 nanotubes by electrochemical anodization following the hydrothermal method to enhance the photocatalytic degradation. Optical studies revealed a reduction in the bandgap (2.12 eV) of CuO-modified TiO2 nanotubes, which plays an important role in increasing the photocatalytic activity. The effect of CuO loading on TiO2 nanotubes in photocatalytic degradation as well as the effect of bias and H2O2 on photo-electrocatalytic degradation were studied. In photocatalytic degradation, 0.05 M CuO–TiO2 photocatalyst produced a maximum degradation of 49.5 % in 8 h. Compared with the pristine TiO2 nanotubes, the photodegradation of CuO-loaded TiO2 nanotubes increased by 16 %. Furthermore, when an external bias was applied, the photodegradation efficiency increased by 36 %. In addition of H2O2 to the PEC system, 0.05 CuO–TiO2 photocatalyst produced 100 % degradation of methyl violet in 2.5 h. Reusability studies showed that the photocatalysts are stable and can therefore be used for practical applications such as photocatalytic degradation and photoelectrochemical degradation of methyl violet.

Enhanced Degradation of Carbamazepine from Constructed Wetlands with a PEC System Based on an Anode of N-TiO2 Nanocrystal-Modified TiO2 Nanotubes and an Activated Carbon Photocathode

Enhanced Degradation of Carbamazepine from Constructed Wetlands with a PEC System Based on an Anode of N-TiO2 Nanocrystal-Modified TiO2 Nanotubes and an Activated Carbon Photocathode

The impact of suspended particulate matters on metals removal from water using a three-combined-dimensional photo-electrocatalytic reactor (case study: Sefidrud dam)

The Sefidrud dam's water contamination poses a significant health risk to millions of people. A study aimed to investigate the impact of water impurities (mostly emerging as suspended matter particles) and redox potential on the removal of heavy metals like copper, zinc, cadmium, and arsenic through a photo-electrocatalytic process. A three-dimensional photo electrocatalytic reactor with microparticles of Ti/TiO2 was used for experiments. Central Composite Design (CCD) response surface methodology was employed for optimization. The results showed removal rates of 78 % for copper, 68 % for zinc, 57 % for cadmium, and 38 % for arsenic under optimal conditions. The removal rates increased to 94 %, 86 %, 65 %, and 52 % for copper, zinc, cadmium, and arsenic in response to increased dissolved oxygen. Redox potential was found to be a governing parameter during the photo electrocatalytic removal of zinc. Furthermore, microparticles improved the removal percentage of copper and arsenic in acidic environments. Finally, chemical fractional analysis revealed that the presence of suspended matter particles (SPMs) has a detrimental impact on the performance of PEC systems. This was attributed to the desorption of metals from exchangeable and Fe-Mn bounds of SPMs during the PEC process.

Rational Design of CoOOH/α-Fe2O3/SnO2 for Boosted Photoelectrochemical Water Oxidation: The Roles of Underneath SnO2 and Surface CoOOH.

Hematite (α-Fe2O3) photoanode is a promising candidate for efficient PEC solar energy conversion. However, the serious charge recombination together with the sluggish water oxidation kinetics of α-Fe2O3 still restricts its practical application in renewable energy systems. In this work, a CoOOH/α-Fe2O3/SnO2 photoanode was fabricated, in which the ultrathin SnO2 underlayer is deposited on the fluorine-doped tin oxide (FTO) substrate, α-Fe2O3 nanorod array is the absorber layer, and CoOOH nanosheet is the surface modifier, respectively. The resulting CoOOH/α-Fe2O3/SnO2 exhibited excellent PEC water splitting with a high photocurrent density of 2.05 mA cm-2 at 1.23 V vs RHE in the alkaline electrolyte, which is ca. 3.25 times that of bare α-Fe2O3. PEC characterizations demonstrated that SnO2 not only could block hole transport from α-Fe2O3 to FTO substrate but also could efficiently enhance the light-harvesting property and reduce the surface states by controlling the growth process of α-Fe2O3, while the CoOOH overlayer as cocatalysts could rapidly extract the photogenerated holes and provide catalytic active sites for water oxidation. Benefiting from the synergistic effects of SnO2 and CoOOH, the efficiency of the charge recombination and the overpotential for water oxidation of α-Fe2O3 are obviously decreased, resulting in the boosted PEC efficiency for water oxidation. The rational design and simple fabrication strategy display great potentials to be used for other PEC systems with excellent efficiency.

Dehydrogenative cyclization of 2-arylbenzoic acid and 2-arylbenzamide with hydrogen evolution in a photoelectrochemical cell.

This paper describes photoelectrochemical dehydrogenative cyclization of 2-arylbenzoic acid and 2-arylbenzamide in a PEC cell consisting of a mesoporous WO3 photoanode and Pt cathode. The cyclization reaction is effectively driven by this PEC system at room temperature with blue LED irradiation under external oxidant- and metal-free conditions, delivering a series of benzolactones and benzolactams in up to 95% isolated yields. Meanwhile, hydrogen is released as the only byproduct of this process.

Unassisted photoelectrochemical hydrogen peroxide production over MoOx-supported Mo on a Cu3BiS3 photocathode

MoOx-supported Mo enhances peroxide adsorption strength and electron transport, enhancing H2O2 production efficiency in Cu3BiS3-based photocathode. Finally, unbiased PEC–PEC system coupled with perovskite photoanode shows efficient H2O2 production.

Barriers and facilitators for developing a prehospital emergency care system evaluation tool (PEC-SET) for low-resource settings: a qualitative analysis

ObjectivesStrengthening of emergency care systems, including prehospital systems, can reduce death and disability. We aimed to identify perspectives on barriers and facilitators relating to the development and implementation of a...

Design and investigation of photoelectrochemical water treatment using self-standing Fe3O4/NiCo2O4 photoanode: In-situ H2O2 generation and fenton-like activation

Photoelectrocatalytic advanced oxidation processes (PEC AOPs) show great promise for solar-driven water treatment due to their energy efficiency and environmental compatibility. This study focuses on two key aspects: 1) creating an efficient photoanode and 2) utilizing the cathodic process simultaneously to enhance water treatment. Herein, a self-standing photoanode with stemmed nanospikes made from Fe3O4@NiCo2O4 (FNCO) was developed and seamlessly integrated into a PEC system. FNCO photoanode significantly improves PEC cell performance, using half the energy (12 Wh/g-pollutant) and achieving a four-fold higher rate constant (7.9×10−2 s−1) compared to NiCo2O4 (NCO). The in-situ generation of H2O2 and its Fenton-like activation amplifies the generation of reactive oxygen species (ROS), contributing to the PEC degradation activity. Detailed analysis reveals that the presence of surface-Fe3O4 enhances surface hydrophilicity and contributes to the high density of catalytically active sites in FNCO. We conducted a comprehensive investigation into the in-situ formation and activation pathways of H2O2 molecules through a series of experiments. The designed PEC water treatment system achieved almost 60 % total organic carbon (TOC) removal efficiency with consistent performance across a range of real-world water treatment scenarios, underscoring its versatility and robustness.

Controlled crystal facet of tungsten trioxide photoanode to improve on-demand hydrogen peroxide production for in-situ tetracycline degradation

Advanced oxidation processes utilizing hydrogen peroxide (H2O2) are widely employed for the treatment of organic pollutions. However, the conventional anthraquinone method for H2O2 synthesis is unsuitable for this application owing to its hazardous and costly nature. Alternative approaches involve a photoelectrochemical method. Herein, tungsten trioxide (WO3) photoanode has been used for the conversion of H2O into H2O2 through oxidation reaction from a PEC system, simultaneously utilizing in-situ generated hydroxyl (OH•) radicals for tetracycline degradation. By manipulating the ratio of crystal facets between (020) and (200) of the WO3 photoanode, a significant improvement in H2O2 production has been achieved by increasing the proportion of (020) facet. The production rate of WO3 photoanode enriched with the (020) facet is approximately 1.9 times higher than that enriched with (200) facet. This enhanced H2O2 production performance can be attributed to the improved formation of OH• radicals and the accelerated desorption of H2O2 on the (020) facet. Simultaneously, the in-situ generated OH• radicals are applied for tetracycline degradation. Under illumination of sunlight stimulator for 180 min, the optimal photoanode achieves a degradation rate of 86.7% for tetracycline. Furthermore, the resulting chemicals have been analyzed, revealing that C8H10O and C7H8O were formed as the primary products. Notably, these products exhibit significantly lower toxicity compared to tetracycline. This study presents a promising approach for the rational design of WO3 based photoanodes for oxidation reaction, including not only H2O2 production but also the efficient degradation of organic pollutants.

Development of ABO4‐type photoanodes for photoelectrochemical water splitting

AbstractPhotoelectrochemical (PEC) water splitting with zero carbon emissions is a promising technology to solve the global issues of energy shortage and environmental pollution. However, the current development of PEC systems is facing a bottleneck of low solar‐to‐hydrogen (STH) efficiency (<10%), which cannot meet the demand of large‐scale H2 production. The development of low‐cost, highly active, and stable photoanode materials is crucial for high STH efficiency of PEC water splitting. The recent development of BiVO4 as photoanode materials for PEC water splitting has been a great success, and ABO4‐type ternary metal oxides with a similar structure to BiVO4 have high development potential as efficient photoanodes for high‐performance PEC water splitting. The design and development of ABO4 photoanodes for PEC water splitting are critically reviewed with special emphasis on the modification strategies and performance improvement mechanisms of each semiconductor. The comprehensive analysis in this review provides guidelines and insights for the exploration of new high‐efficiency photoanodes for solar fuel production.

(Invited) P-Doped Hematite for Efficient Photoelectrochemical Water Splitting

In this talk, I would like to discuss about how a simple in-situ phosphorus (P) doping strategy improves the overall PEC performance of hematite. By introducing enriched FePO4 regions on the Ti-doped FeOOH surface and subsequent high-temperature annealing, P,Ti co-doped Fe2O3 (P,Ti-Fe2O3) nanorods were fabricated. P,Ti-Fe2O3 not only increased the conductivity by creating oxygen vacancies but also generated a porous structure inside the hematite. Benefiting from the efficient P doping effects, the resulting P,Ti-Fe2O3 photoanode exhibited 94% improved photocurrent density compared to that of Ti-Fe2O3 (@ 1.23 VRHE) under 1 sun illumination. After applying the co-catalyst, NiFeOx/P,Ti-Fe2O3showed significantly enhanced photocurrent density (3.54 mA cm-2 at 1.23 VRHE) with a 108 mV cathodic shift. Our study suggests a new approach for achieving porous hematite and a highly efficient PEC system by a simple and cost-effective nonmetal P-doping method.

Dielectric relaxation and ionic conduction in solid polymer electrolyte based on a random copolymer of ethylene carbonate and ethylene oxide

Broadband dielectric spectroscopy (BDS) is a powerful technique for studying the dielectric and ion-conductive behavior of solid polymer electrolytes (SPE). In this study a random copolymer of ethylene carbonate (EC) and ethylene oxide (EO), P(EC/EO), was used as a polymer host for SPE, and the correlation between dielectric relaxation and ionic conduction in P(EC/EO)-LiFSI electrolytes was studied. BDS measurements revealed that the DC conductivity for P(EC/EO) electrolytes is higher than for the PEC system at all salt concentrations. This is due to the much higher a-relaxation frequency, indicating that the randomly introduced EO units can provide fast segmental motion with no formation of any stable coordination structures with Li ions. FT-IR analysis indicated that the peak fraction of C = O interacting with Li ions was small, less than 10% in the 10 mol% electrolyte, but in concentrations above 40 mol% the proportion was nearly saturated at around 60–70%. A small CO-C peak interacting with Li ions appears at 1080 cm−1, but no change in peak intensity is observed, implying no formation of stable coordination structures that reduce the glass transition temperature.

Photovoltaic-Assisted Photo(electro)catalytic Hydrogen Production: A Review

The idea of supporting the Sustainable Development Goals (SDGs) has inspired researchers around the world to explore more environmentally friendly energy generation and production methods, especially those related to solar and hydrogen energy. Among the various available sustainable energy technologies, photo(electro)catalytic hydrogen production has been competitively explored, benefiting from its versatile platform to utilize solar energy for green hydrogen production. Nevertheless, the bottleneck of this photo(electro)catalytic system lies within its high voltage required for water electrolysis (>1.23 V), which affects the economic prospects of this sustainable technology. In this regard, coupling the photo(electro)catalytic system with a solar-powered photovoltaic (PV) system (PV-PEC) to unleash the fascinating properties and readiness of this system has heightened attention among the scientific community. In this context, this review begins by elucidating the basic principles of PV-PEC systems, followed by an exploration of various types of solar PV technology and the different types of semiconductors used as photocatalysts in the PEC system. Subsequently, the main challenges faced by the PV-PEC system are presented, covering areas such as efficiency, stability, and cost-effectiveness. Finally, this review delves into recent research related to PV-PEC systems, discussing the advancements and breakthroughs in this promising technology. Furthermore, this review provides a forecast for the future prospects of the PV-PEC system, highlighting the potential for its continued development and widespread implementation as a key player in sustainable hydrogen production.

MoSe2 nanoflakes decorated ZnO nanorods: An effective photoelectrode with S-scheme heterojunction for photoelectrocatalytic degradation of tetracycline and rhodamine B

Photoelectrocatalysis has been extensively used as one of the most widely known advanced oxidation processes (AOPs) owing to its superiority over photocatalytic systems with regards to the reduced recombination of charge carriers. ZnO demonstrates profound performance in PEC systems, and to overcome the obstacle of its limited visible light utilization, heterojunction formation of transition metal dichalcogenides (TMDs) with this classical semiconductor is proposed. Herein, MoSe2 was introduced onto ZnO nanorods to widen its visible light absorption and consequently boost the PEC ability of the proposed composite in omitting model organic contaminants in water. The as-synthesized nanocomposite was immobilized onto FTO by Electrophoretic deposition (EPD) technique which is then represented as the working electrode in the three-electrode PEC system. The characterization of the proposed nanocomposite was attained by techniques including: XRD, FESEM, FTIR, DRS and EDX. Moreover, electrochemical characterization was conducted to study its electrochemical properties. The PEC activity of the samples was studied by the degradation of Rhodamine B dye (62.3%) and tetracycline pharmaceutical (70.2%) under irradiation. The results indicated a much higher PEC ability for ZnO NR/MoSe2/FTO photoelectrode than its bare parent samples as well as its recyclability. To study the impact of the operational parameters, the electrolyte's concentration, initial pH, external bias voltage and initial concentration of the contaminant were investigated. By means of the scavenging tests, electrons and holes have the highest and the lowest importance in the PEC reaction, respectively. The S-scheme mechanism of degradation was proposed based on the cumulative experimental data.

Bimetallic systems of ZnO/Al/Ag applied on cell PEC and photocatalytic system

The synthesis of bimetallic systems of ZnO/Al/Ag deposited on glass substrate was carried out by the combination of sol-gel and spin-coating methods, used as an easy and simple alternative to prepare this kind of films, in comparison with other reported methods. Structural parameters and morphology on the surface of bimetallic films were determined by analytic techniques. While band gap value was calculated by Tau graph through UV–Vis analysis. Photocatalytic and photoelectrochemical tests were also carried out to analyze the behavior of the films and the effect provided by the metallic elements. Results showed that films with bimetallic elements have an improved behavior in terms of charge transfer observed in the PEC cell, where values of up to 0.8 mA/cm2 were obtained for ZnO with 80 wt% of Al and 20 wt% of Ag (ZnO/80/20). In fact, this film produces the highest amount of hydrogen reaching 53 μmol of H2 after 3 h of reaction because of the synergy presented by the metallic elements, which increases the electron transport due to the longer service life and fast diffusion rate, but also diminish the depletion layer allowing that electrons will have to travel a smaller distance before reacting.

Incorporating Mesoporous Anatase TiO2 Spheres to Conductive Carbon Black Filled PVDF Membrane for Self-Cleaning Photo(electro)catalytic Filtration

Polyvinylidene fluoride (PVDF) membranes have been widely used for micro/ultrafiltration. However, their hydrophobicity leads to serious membrane fouling over time during the process of dye decolorization, which limits their practical application. Herein, PVDF, mesoporous TiO2 spheres (MTS, ∼460 nm), and carbon black (CB) are strategically hybridized via a polyvinylpyrrolidone (PVP)-assisted phase inversion method. The fabricated PVDF/CB/TiO2 conductive membrane prepared by optimal low-molecular-weight PVP (10 kDa) shows a highly porous structure with macro-voids, and MTS are firmly incorporated into the PVDF/CB membrane matrix with a morphologically intact structure, rendering the ternary and conductive membranes with excellent PEC properties. The decolorization rate of 0.50 mg/L methylene blue (MB) reaches 98.6% under the condition of 1.0 V bias potential and simulated solar light irradiation in a continuous cross-flow filtration process. The •O2– and •OH radicals and photogenerated holes (h+) are mainly responsible for MB decolorization in the PEC system. Our work provided a sustainable and efficient method for dye decolorization by combining the PEC system and membrane technology.