Search Results (440)

Industrial effluents containing persistent synthetic dyes represent an important environmental challenge because of their high chemical stability, low biodegradability, and potential adverse effects on aquatic ecosystems. This study evaluates electrochemical advanced oxidation processes (EAOPs) as remediation strategies for dye-contaminated tanery dyes, with particular emphasis on conditions representative of complex industrial effluents. Electrochemical oxidation (EOx), electro-Fenton (EF), and photoelectro-Fenton (PEF) processes using boron-doped diamond (BDD) electrodes were comparatively investigated for the degradation of Violet S4B and a multicomponent mixture containing Violet S4B, Brown DR, and Black NT2. The effects of current density and pollutant concentration were assessed through discoloration, pseudo-first-order kinetics, chemical oxygen demand (COD) removal, and HPLC analysis of oxidation intermediates. For the multicomponent system, PEF achieved approximately 99% discoloration after 120 min, compared with nearly 97% for EF and 95% for EOx, with apparent rate constants increasing in the order EOx < EF < PEF. More importantly, COD analysis demonstrated extensive mineralization during PEF treatment, while HPLC revealed negligible accumulation of oxalic acid, indicating effective oxidation of refractory intermediates. The results demonstrate that combining anodic oxidation, electrochemically generated Fenton chemistry, and photo-assisted reactions enhances the remediation of complex dye mixtures. These findings support BDD-based EAOPs, particularly PEF, as promising technologies for reducing persistent organic pollution associated with tannery dye solutions. Full article

Developing cost-effective photocatalysts with high activity remains a key challenge in photocatalysis. In this study, a low-cost nickel phosphide (Ni₂P) cocatalyst was combined with MIL-53(Fe) to fabricate Ni₂P/MIL-53(Fe) nanocomposites via a simple hydrothermal method. The as-prepared composites were systematically characterized by XRD, FT-IR, SEM, UV-vis DRS, PL, and EIS to evaluate their structural, morphological, optical, and electrochemical properties. The introduction of Ni₂P significantly promoted the separation of photogenerated electron–hole pairs on the MIL-53(Fe) surface, thereby enabling valence band holes (h⁺) to participate in alcohol oxidation, as confirmed by photoelectrochemical analysis. Under optimized conditions, the Ni₂P/MIL-53(Fe) nanocomposite achieved a significant photocatalytic alcohol conversion rate of 74%, which is 7.4-fold and 2.5-fold higher than those of pristine Ni₂P and MIL-53(Fe), respectively. Furthermore, mechanistic studies revealed that valence band holes are primarily responsible for the selective oxidation of aromatic alcohols. Full article

Crystalline oxide microfeatures offer optical, electronic, catalytic, and interfacial functions, but their fabrication often requires templates, patterned scaffolds, or serial machining. A template-free route converted an electrodeposited Cu₂O coating on Au(111)/Si into substrate-supported vertical microfeatures by anodization at a nominal cell voltage of 10 V in 0.002 mol L⁻¹ Na₂S₂O₈ at 277 K. FE-SEM showed progressive widening of the pre-existing intercolumnar network and narrowing of the retained features. This spatially non-uniform removal identifies preferential dissolution along the intercolumnar network as the principal removal pathway at the coating-morphology scale. From 1 to 8 min, the within-image mean and median feature widths decreased by 36.0% and 45.9%, respectively. The dominant out-of-plane Cu₂O(111) diffraction signature was retained while mean visible reflectance decreased. The Cu-H₂O potential-pH framework provides a qualitative thermodynamic guide to possible oxidative pathways that are evaluated against the experimental evidence. C 1s-referenced XPS provides direct ex situ evidence of an anodization-associated Cu(II)/CuO-like contribution at the outermost surface. Chopped photoelectrochemical measurements showed the largest condition-level light–dark current density contrast after short anodization, providing a secondary functional comparison of the completed coatings. Full article

Three types of meso-substituted manganese(III) porphyrin complexes with phenyl, propyl, and isopropyl substituents were synthesized to examine their photochemical and electrochemical properties. The distortion of the porphyrin rings and redox potentials depended on the substituents. The fluorescence quantum yields of these porphyrins were significantly low, indicating the rapid deactivation of their singlet excited states. Although weak emissions attributed to higher singlet excited states and charge-transfer states were observed, their quantum yields remained low. Redox potential measurements showed the relatively strong photooxidative ability of these porphyrins from a thermodynamic standpoint. However, photosensitized protein oxidation was barely observed. The rapid deactivation of photoexcited states decreases the probability of photochemical reactions including biomolecule oxidation. These porphyrins suppressed the self-oxidation of photo-irradiated 1-benzyl-1,4-dihydronicotinamide and catalyzed the decomposition of hydrogen peroxide. In conclusion, these manganese(III) porphyrin complexes barely showed photooxidation activity toward biomolecules and demonstrated protective action against phototoxic reactions. Full article

Photoelectrochemical (PEC) energy conversion is a promising approach for solar-to-chemical fuel production, but its practical performance is limited by insufficient visible-light utilization and charge-carrier recombination. Here, poly(3,4-ethylenedioxythiophene) (PEDOT)-centered TiO₂ hybrid electrodes were prepared by electropolymerizing PEDOT on FTO substrates, followed by electrochemical doping/dedoping treatment and coating with commercial TiO₂ as a model oxide semiconductor. SEM, EDS, and LIBS analyses confirmed the successful deposition of TiO₂ onto PEDOT-based films. Four-probe measurements showed that electrochemical doping reduced the apparent resistance of PEDOT-based electrodes, while UV–vis spectroscopy revealed enhanced long-wavelength absorption for doped PEDOT-containing films. PEC measurements using TiO₂, PEDOT, and TiO₂–PEDOT electrodes showed that PEDOT-containing electrodes exhibited much stronger photoresponses than commercial TiO₂ alone under both HER- and OER-relevant conditions. The TiO₂–PEDOT electrode showed stable photocurrent responses under chopped illumination and retained photoresponse under illumination transmitted through a 410 nm UV-cut filter, supporting the primary role of PEDOT in visible-light utilization. Long-term chronoamperometry further showed that TiO₂–PEDOT retained approximately 99.0% of its cathodic current under HER-relevant conditions and 91.9% of its anodic current under OER-relevant conditions after 5200 s of continuous illumination. The improved response of TiO₂–PEDOT compared with PEDOT alone suggests that TiO₂/PEDOT physical contact may assist interfacial charge separation and transport. These findings demonstrate that PEDOT-centered metal oxide/conducting polymer hybrids provide a useful model platform for visible-light-responsive PEC energy-conversion applications. Full article

The development of efficient visible-light-driven semiconductor photocatalysts is essential for scalable and sustainable green hydrogen production. Among ternary metal oxides, MV₂O₆ (M = Zn, Ni, Cu, Mn, Co, etc.) metavanadates have attracted considerable interest because of their narrow band gaps (~1.8–2.5 eV), strong visible-light absorption, and unique edge-sharing VO₆ octahedral framework that promotes charge separation. This review summarizes recent advances in the design, synthesis, and electronic engineering of MV₂O₆-based photocatalysts for solar water splitting. Since direct particulate overall water splitting has only been demonstrated for MnV₂O₆, whereas ZnV₂O₆, NiV₂O₆, and CuV₂O₆ have mainly been investigated as photoelectrodes, both particulate photocatalytic and photoelectrochemical (PEC) systems are critically examined. The review clearly distinguishes these two configurations, highlighting how PEC studies provide valuable insights into charge transport, interfacial processes, and reaction kinetics while recognizing the additional challenges associated with suspension-based photocatalysis. Fundamental crystal structures, electronic band alignments, and charge-transfer characteristics of MV₂O₆ compounds are discussed, followed by recent advances in synthesis strategies, including hydrothermal, sol–gel, and deep eutectic solvent (DES)-assisted methods, together with morphology and defect engineering. Particular attention is given to oxygen-vacancy formation and its influence on visible-light absorption and charge separation. Modification strategies, including elemental doping, cocatalyst loading, and the construction of Z-scheme and step-scheme (S-scheme) heterojunctions, are critically evaluated for improving photocatalytic efficiency. Finally, the review discusses the key challenges that limit practical applications, including unfavorable band-edge positions, rapid carrier recombination, sluggish surface reaction kinetics, photostability, and the need to establish composition–structure–activity relationships. Future perspectives emphasize rational materials design through advanced characterization, theoretical calculations, and scalable synthesis approaches to accelerate the development of efficient MV₂O₆ photocatalysts for solar-driven hydrogen production. Full article

Aquaculture has rapidly expanded, surpassing capture fisheries and playing a vital role in global food security. However, this growth raises environmental concerns, especially regarding nitrogen waste accumulation in recirculating aquaculture systems (RASs). Nitrogen compounds from uneaten feed and fish excreta, mainly ammonia (NH₃) and nitrite (NO₂⁻), lead to water pollution, eutrophication, and greenhouse gas emissions. This study describes the setup and the efficiency of a new photo-electrocatalytic (PEC) system in reducing nitrogen waste in a high-density RAS for rainbow trout (30 kg/m³). The PEC system, an evolution of a pure photocatalytic system, was integrated in the units of the RAS and tested for the first time in field conditions, combining photocatalysis and electrochemical oxidation to convert toxic nitrogen species (NH₃) into less harmful nitrogen forms (NO₃⁻ and N₂), aiming to mitigate both water and atmospheric pollution. Over a 4-week period, water nitrogen compounds, ammonia and greenhouse gases (carbon dioxide, nitrous oxide and methane) emitted by water were continuously monitored in two groups of three tanks (PEC vs. control). Each tank was equipped as an independent RAS unit. PEC treatment led to significantly lower NH₃ concentrations (0.96 ± 0.2 mg/L vs. 1.78 ± 0.2 mg/L, p < 0.01), lower NO₂⁻ levels and higher NO₃⁻ levels (61.77 ± 2.14 mg/L vs. 53.10 ± 2.14 mg/L, p < 0.01) in water, indicating efficient nitrogen oxidation. Gaseous emissions were also reduced: NH₃ (1.49 vs. 2.64 mg/m²/day, p < 0.05) and N₂O (1.44 vs. 2.88 mg/m²/day, p < 0.05). These results support PEC technology as a promising solution for improving nitrogen management in intensive aquaculture. Although challenges remain in optimizing energy use and scalability, PEC offers a valuable strategy for reducing environmental impact while sustaining productivity in the aquaculture industry. Full article

Copper oxide (CuO) is a narrow-bandgap p-type semiconductor promising for visible-light photocatalysis, yet it suffers from rapid charge recombination and low carrier transfer efficiency. In this study, two distinct CuO photocatalysts were fabricated via different routes: two-dimensional CuO nanosheets derived from annealing a CuBDC metal–organic framework (MOF) precursor, and oriented one-dimensional CuO nanoflower arrays prepared by electrochemical deposition, followed by annealing. The crystal structure, morphology, optical absorption, and photoelectrochemical properties were systematically characterized by XRD, SEM, XPS, UV-Vis spectroscopy, transient photocurrent response, EIS, and PL spectroscopy. The CuO nanoflower thin film exhibits a broad visible-light absorption, a markedly higher photocurrent density (42.25 μA cm⁻²), and lower charge-transfer resistance compared to CuO nanosheets. When evaluated for visible-light photocatalytic degradation of methylene blue (MB), rhodamine B (RhB), and malachite green (MG), the CuO thin film completely degraded MB within 15 min, with an apparent rate constant of 20.15 h⁻¹—approximately three times that of CuO nanosheets. It also showed 1.2- and 1.28-fold higher activity for RhB and MG, respectively. The enhanced performance is attributed to the oriented nanoflower architecture that provides continuous charge transport pathways, suppresses carrier recombination, and extends light propagation via multiple reflections. This work demonstrates that microstructural engineering is an effective strategy to overcome the intrinsic limitations of CuO photocatalysts for wastewater treatment. Full article

Elucidating structure–activity relationships in semiconductor photocatalysis has been significantly impeded by the inherent limitations of ensemble-averaged characterization techniques, which obscure the spatiotemporal heterogeneity intrinsic to catalytic surfaces. Single-molecule fluorescence microscopy (SMFM) surmounts this bottleneck by offering nanometer-scale spatial resolution coupled with the capacity to resolve single-turnover events. Herein, we provide a comprehensive overview of the State-of-the-Art applications of fluorogenic probe-coupled SMFM in deciphering the microscopic mechanisms governing photocatalysis. We begin by delineating the operational principles of total internal reflection fluorescence (TIRF) microscopy and categorizing the response mechanisms of three distinct classes of fluorogenic probes: oxidative (e.g., Amplex Red, APF), reductive (e.g., Resazurin, DN-BODIPY), and acidic (e.g., furfuryl alcohol, thiophene) reporters. Subsequently, we highlight seminal studies wherein SMFM has been leveraged to visualize facet-dependent charge separation on model photocatalysts—including TiO₂, BiOBr, and InSe—to map the dynamic activity associated with surface defects and to precisely locate active sites during photoelectrochemical water splitting. Finally, we critically assess the prevailing technical challenges, such as limitations in probe specificity and background interference, while offering a perspective on prospective avenues for methodological refinement. This review is intended to serve as a methodological cornerstone for advancing mechanistic understanding in photocatalysis and for guiding the rational design of high-performance catalysts. Full article

In this study, polyhedral self-assembled spherical titania (TS) photocatalyst was successfully synthesized via a one-step hydrothermal method from titanium chloride, sodium dodecyl sulfate and sulfuric acid. Titania modification with iron was carried out through the same procedure by the addition of different amounts of iron(III) chloride to the substrate mixture. Various methods were applied for sample characterization, e.g., XRD, SEM, TEM, XPS, UV-vis DRS, and photo-electrochemical measurements, such as EIS, CV, transient photocurrent, whereas photocatalytic activity was investigated for hydrogen evolution under UV/vis and oxidative decomposition of antibiotics under UV and/or vis, including also tests with scavengers. It has been found that iron was both incorporated in the titania structure (doping) and adsorbed on its surface. Although iron presence has hardly influenced the properties (slight changes in morphology, bandgap energy, and crystallite size), the photocatalytic activity has increased significantly. Therefore, it is proposed that iron might work as an electron sink, hindering the charge carriers’ recombination. Linear evolution of hydrogen, recycling experiments and characterization of samples after recycling have confirmed a good stability of iron-modified titania. Full article

The concurrent accumulation of plastic waste and CO₂ emissions poses a critical environmental challenge while presenting a compelling opportunity for integrated carbon management. Coupled plastic waste reforming and CO₂ conversion has recently emerged as a promising strategy to valorize these abundant waste streams into fuels and value-added chemicals, enabling a closed carbon cycle. This review systematically summarizes recent advances in integrated electrochemical and photoelectrochemical systems for the co-conversion of plastic waste and CO₂. Fundamental reaction pathways, including plastic depolymerization, reforming, and oxidation, are discussed in conjunction with their thermodynamic and kinetic coupling to CO₂ reduction. Particular emphasis is placed on paired electrochemical processes, such as plastic-derived alcohol oxidation coupled with CO₂ reduction processes, all of which offer enhanced energy efficiency. Photoelectrochemical approaches driven by renewable energy are further highlighted for their potential to operate under mild conditions. In addition, key design strategies for catalysts and electrodes—focusing on earth-abundant materials, redox stability, interfacial engineering, and selectivity control—are critically evaluated. Finally, current challenges and future opportunities are outlined to accelerate the development of scalable, efficient, and sustainable technologies for circular chemical manufacturing. Full article

To minimize the influence of interface states and surface damage, by inserting a gate oxide layer, the photoelectrochemical oxidation method was utilized to directly grow the gate oxide layer while simultaneously creating the gate-recessed regions onto gallium nitride (GaN)-based single-gate and dual-gate metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs). Compared to the single-gate structure, the two-dimensional electron gas (2DEG) channel layer was also modulated by the auxiliary gate, in addition to being modulated by the main gate. Consequently, a wider transconductance range, larger saturation drain-source current, lower gate leakage current, and higher drain-source breakdown voltage were the benefits derived from the auxiliary gate functionality in the dual-gate devices. Moreover, the low-frequency noise characteristics of the GaN-based MOS-HEMTs could also be improved by the dual-gate structure. These experimental results demonstrated that incorporating a dual-gate structure and directly grown gate oxide layers onto GaN-based MOS-HEMTs is a promising alternative for GaN-based low-noise, high-power, and high-frequency applications. Full article

Graphene oxide (GO) was employed as an additive to improve the electrochemical activity of zinc oxide (ZnO) used as both a photoelectrocatalyst for water splitting and an electrochemical sensor for detection of diclofenac. To comprehend the influence of a small amount of GO on the electrochemical activity of ZnO, a series of ZnO/xGO (x = 0, 0.1, and 0.5) particles was synthesized by microwave processing of Zn(OH)₂ precipitate in the presence of 0.1 and 0.5 wt.% of previously prepared GO. The phase composition and crystal structure ordering of ZnO/xGO particles were investigated by XRD and Raman spectroscopy. The optical properties were studied by UV–Vis DRS and PL spectroscopy. The particle morphology was inspected by FE–SEM while the textural properties were analyzed by the low-temperature nitrogen adsorption–desorption method. The (photo)electrocatalytic and electrochemical sensing activities were examined on the ZnO/rxGO modified glassy carbon electrodes (GCEs) prepared by in situ reduction of the ZnO/xGO modified GCEs for 120 s. The electro- and photoelectrocatalytic activity of ZnO/rxGO modified GCEs for water splitting was tested in dark conditions and after 60 min under illumination, respectively, employing linear sweep voltammetry in 0.1 M NaOH and 0.1 M H₂SO₄ as electrolytes. The electrochemical sensing activity of ZnO/rxGO modified GCEs was tested for detection of diclofenac in aqueous solution. The improvement in the electrochemical activity of ZnO was correlated with the added amount of GO, structural defects, and particle morphology. Full article

A ternary CdS–MoS₂–rGO photocathode was developed to enhance visible light-driven hydrogen evolution through interfacial heterostructure engineering. The composite was fabricated via a solution-based deposition method followed by thermal conversion, resulting in crystalline CdS and MoS₂ phases that were uniformly integrated within a conductive reduced graphene oxide (rGO) framework. Structural and surface analyses (XRD and XPS) confirmed the coexistence of Cd²⁺, Mo⁴⁺, and S²⁻ chemical states without detectable secondary phases. Photoelectrochemical measurements revealed that the ternary architecture significantly improves charge separation efficiency and interfacial charge-transfer kinetics compared to binary and single-component films. The CdS–MoS₂–rGO photocathode exhibited the highest photocurrent density, reduced charge-transfer resistance, and favorable Tafel slope under visible-light irradiation (0.25 sun, neutral electrolyte). Gas chromatography measurements verified that these electrochemical enhancements translate into increased hydrogen production rates, following the trend: CdS–MoS₂–rGO > CdS–rGO > MoS₂–rGO >> rGO. Applied bias photon-to-current efficiency (ABPE) analysis further confirmed improved photon utilization efficiency in the ternary system. The enhanced performance is attributed to synergistic integration of CdS (light harvesting), rGO (rapid electron transport), and MoS₂ (catalytic edge sites), which suppresses recombination and accelerates proton reduction kinetics. These findings demonstrate that rational multi-component heterostructure design is an effective strategy for improving hydrogen evolution rate under mild operating conditions. Full article

Hydrogen peroxide (H₂O₂) is an important green oxidant, and developing efficient visible-light-driven routes for its synthesis is highly desirable. Herein, a CN/Zn_V-ZCS composite photocatalyst was constructed by coupling g-C₃N₄ (CN) with Zn-vacancy-containing ZnCdS (Zn_V-ZCS) for photocatalytic H₂O₂ production. The optimized CN/Zn_V-10 delivered 44.58 mmol g⁻¹ H₂O₂ within 60 min under 425 nm LED irradiation, outperforming pristine CN, ZCS, Zn_V-ZCS, and vacancy-free CN/ZCS, with good cycling stability. Trapping and EPR results identify O₂ as the key electron acceptor and ·O₂⁻ as an important intermediate. Structural characterization and XPS results indicate successful Zn-vacancy introduction, intimate heterointerface formation, and interfacial electron redistribution. Combined VB-XPS, photoelectrochemical, and reactive-species analyses suggest that Zn vacancies are favorable for O₂ adsorption/activation, whereas the CN/Zn_V-ZCS heterointerface promotes charge separation and migration. Based on the available evidence, a Z-scheme interfacial charge-transfer pathway is established in the CN/Zn_V-ZCS system. Full article