Search Results (427)

In this study, we have investigated heterostructural TiO₂/BiVO₄ anodes to determine the effect of the amount and form of BiVO₄ nanoparticles on TiO₂ on the response of photoanodes under UV and visible illumination. BiVO₄ nanopowders were prepared and annealed at temperatures ranging from 200 to 500 °C. Structural and optical characterization indicates that as the annealing temperature is increased, a phase transition from a weakly ordered to a dominant monoclinic BiVO₄ phase is observed, which is accompanied by an increase in visible light absorption. Subsequently, the most crystalline powder was utilized to deposit BiVO₄ on nanostructured TiO₂ either as a compact overlayer (drop-casting) or as a progressively grown nanoparticle (TiO₂@S series) in the successive ionic layer adsorption and reaction process (SILAR). Photoelectrochemical measurements were performed, revealing a morphology-dependent photocurrent response under UV and visible illumination. A further increase in the number of cycles systematically increases the photocurrent in the visible light range while limiting the response to UV radiation. The TiO₂@d photoanode demonstrates the highest relative activity within the visible range; however, it also generates the lowest absolute photocurrent, indicating the presence of significant transport and recombination losses within the thick BiVO₄ layer. The results demonstrate that the presence of BiVO₄ nanoparticles on TiO₂ exerts a substantial influence on the separation of charge between semiconductors and the synergistic utilization of photons from the UV and visible ranges. This research yielded a proposed scheme of mutual band arrangement and charge carrier transfer mechanism in TiO₂@BiVO₄ heterostructures. Full article

Hetero-multicomponent metal oxide catalysts are attracting increasing attention for wastewater remediation due to their tunable band structures, synergistic redox activity, and enhanced stability. This review thoroughly evaluates recent progress in the synthesis and application of such catalysts, highlighting Ti–Cu–Zn nanostructures as a representative case study. We examine synthesis approaches—including hydrothermal, biosynthesis, precipitation, and spray-based methods, with additional insight into sol–gel and other less commonly applied techniques—with emphasis on their suitability for constructing layered and multicomponent heterostructures. Mechanistic aspects of photocatalysis, Fenton and Fenton-like processes, adsorption, and electrochemical routes are discussed, with particular focus on charge separation, reactive oxygen species (ROS) generation, and pollutant-specific degradation pathways. Comparative performance metrics against antibiotics, pesticides, dyes, and fertilizers are analyzed, alongside considerations of leaching, reusability, and scale-up potential. Importantly, while significant progress has been made for organic micropollutants, applications in heavy metal remediation remain scarce, highlighting an urgent research gap. By situating Ti–Cu–Zn systems within the broader class of multicomponent catalysts, this review not only synthesizes current advances but also identifies opportunities to expand their role in sustainable wastewater management, including field deployment, regulatory compliance, and integration into decentralized treatment systems. Full article

Two-dimensional carbide crystals (MXenes) are emerging as a promising platform for the development of novel gas sensors, offering advantages in energy efficiency and tunable analyte selectivity. One of the most effective strategies to enhance and tailor their functional performance involves forming hetero-structured composites with metal oxides. In this work, we explore a chemiresistive effect in double-metal MXene of Ti_0.2V_1.8C and its composites with 2 mol. % SnO₂ and Co₃O₄ nanocrystalline oxides toward feasibility tests with alcohol and ammonia vapor probes. The materials were characterized by simultaneous thermal analysis, X-ray diffraction analysis, Raman spectroscopy, and scanning/transmission electron microscopy. Gas-sensing experiments were carried out on composite layers deposited on multi-electrode substrates to be exposed to the test gases, 200–2000 ppm concentrations, at an operating temperature of 370 °C. The developed sensor array demonstrated clear analyte discrimination. The distinct sensor responses enabled a selective identification of vapors through linear discriminant analysis, demonstrating the further potential of MXene-based materials for integrated electronic nose applications. Full article

In situ preparation routes have become central to advancing lead sulfide (PbS) quantum dots (QDs) for solar-energy conversion, owing to their ability to create strongly coupled QD/oxide interfaces that are difficult to achieve with ex situ colloidal methods, along with their simplicity and potential for low-cost, scalable processing. This review systematically examines the fundamental mechanisms, processing levers, and device implications of the dominant in situ approaches successive ionic layer adsorption and reaction (SILAR), voltage-assisted SILAR (V-SILAR), and chemical bath deposition (CBD). These methods enable conformal QD nucleation within mesoporous scaffolds, improved electronic coupling, and scalable low-temperature fabrication, forming the materials foundation for high-performance PbS-based architectures. We further discuss how these in situ strategies translate into enhanced solar-energy applications, including quantum-dot-sensitized solar cells (QDSSCs) and photoelectrochemical (PEC) hydrogen production, highlighting recent advances in interfacial passivation, scaffold optimization, and bias-assisted growth that collectively suppress recombination and boost photocurrent utilization. Representative device metrics reported in recent studies indicate that in-situ-grown PbS quantum dots can deliver photocurrent densities on the order of ~5 mA cm⁻² at applied potentials around 1.23 V versus RHE in photoelectrochemical systems, while PbS-based quantum-dot-sensitized solar cells typically achieve power conversion efficiencies in the range of ~4–10%, depending on interface engineering and device architecture. These performances are commonly associated with conformal PbS loading within mesoporous scaffolds and quantum-dot sizes in the few-nanometer regime, underscoring the critical role of morphology and interfacial control in charge transport and recombination. Recent studies indicate that performance improvements in PbS-based solar-energy devices are primarily governed by interfacial charge-transfer kinetics and recombination suppression rather than QD loading alone, with hybrid heterostructures and inorganic passivation layers playing a key role in modifying band offsets and surface trap densities at the PbS/oxide interface. Remaining challenges are associated with defect-mediated recombination, transport limitations in densely loaded porous scaffolds, and long-term chemical stability, which must be addressed to enable scalable and durable PbS-based photovoltaic and photoelectrochemical technologies. Full article

This paper introduces a streamlined three-step synthesis method for crafting porous Fe₂O₃/ZnO nanofibers (NFs). Initially, Fe₂O₃ nanoparticles (NPs) were synthesized using the hydrothermal method. Subsequently, PVP NFs laden with Fe₂O₃ NPs and zinc salt were synthesized via an electrospinning method. Finally, porous Fe₂O₃/ZnO NFs were fabricated through calcination, resulting in an average diameter of approximately 100 nm. Gas-sensing experiments illuminate that the porous Fe₂O₃/ZnO NFs exhibit outstanding sensitivity, selectivity, and robust long-term stability. Although the response magnitude decreased under high relative humidity (RH) due to competitive adsorption, the sensor maintained distinct detectable responses towards NO₂ vapor at an optimum temperature of 225 °C. Particularly noteworthy is the substantial enhancement in NO₂ sensing properties observed in the Fe₂O₃/ZnO composite compared to pure ZnO NFs. This enhancement can be ascribed to the distinctive microstructure and heterojunction formed between Fe₂O₃ and ZnO. Full article

Hydrogen energy has been recognized as the most promising secondary energy source due to high energy density, abundance, and environmental friendliness. Among hydrogen production techniques, water electrolysis has emerged as a key research focus, owing to its high efficiency, operational simplicity, controllability, and pollution-free nature. However, the anodic oxygen evolution reaction (OER) involves a high overpotential and sluggish kinetics, which severely constrain the overall efficiency of water electrolysis. Transition metal oxide (TMO) catalysts are regarded as promising substitutes for noble-metal-based catalysts, given their advantages of low cost, elemental abundance, tunable electronic structures, and favorable stability. This review systematically elaborates on the reaction mechanisms of TMO catalysts, including the adsorbate evolution mechanism (AEM) and lattice oxygen mechanism (LOM), and summarizes various performance-enhancement strategies, such as morphology control, doping engineering, support engineering, and heterostructure construction. Furthermore, it outlines current challenges and future research directions, covering precise synthesis and structural control, identification of active sites and mechanistic elucidation, and stability and degradation issues, as well as multifunctional applications and broad-pH-range adaptability. The aim is to offer theoretical guidance and technical insights for designing and developing high-performance TMO electrocatalysts. Full article

We report a galvanic replacement-driven strategy for the in situ growth of highly uniform one-dimensional (1D) Cu@CuO-X (X = Ag, Bi) nanobelts directly on aluminum foils. Unlike conventional multi-step coating or hard-template replication strategies, the formation of these heterostructured nanobelts is governed by a spontaneous interfacial galvanic replacement process between Cu and the introduced metal species, ensuring in situ growth and intimate interfacial integration. Comprehensive SEM, TEM, XRD, and XPS characterizations confirm the successful formation of Cu@CuO-Ag and Cu@CuO-Bi architectures, where Bi predominantly exists in the oxidized Bi³⁺ state, forming Bi₂O₃-like surface species. Benefiting from their 1D anisotropic framework and controllable heterointerfaces, this work underscores the distinctiveness and versatility of the self-templated galvanic replacement strategy for the design of multifunctional nanomaterials. Full article

A novel Z-scheme Dy₂TmSbO₇/BiHoO₃ heterostructure photocatalyst was synthesized with the ultrasound-assisted solvothermal method. The Dy₂TmSbO₇/BiHoO₃ heterojunction photocatalyst (DBHP) reflected wonderful separation efficiency of photogenerated electrons and photogenerated holes owing to the efficient direct Z-scheme heterojunction structure characteristic. The lattice parameter and the bandgap energy of the Dy₂TmSbO₇ were 10.52419 Å and 2.58 eV, simultaneously, the lattice parameter and the bandgap energy of the BiHoO₃ were 5.42365 Å and 2.25 eV, additionally, the bandgap energy of the DBHP was 2.32 eV. Above results indicated that DBHP, Dy₂TmSbO₇ or BiHoO₃ possessed an excellent ability for absorbing visible light energy, therefore, DBHP, Dy₂TmSbO₇ or BiHoO₃ owned superior photocatalytic activity for degrading the sulphamethoxypyridazine (SMP) under visible light irradiation. The removal rate of the SMP after visible light irradiation of 135 min with the DBHP was 99.47% for degrading the SMP during the photocatalytic degradation (PADA) process, correspondingly, the removal rate of the total organic carbon (TOC) concentration after visible light irradiation of 135 min with the DBHP was 98.02% for degrading the SMP during the PADA process. The removal rate of the SMP after visible light irradiation of 135 min with the DBHP was 1.15 times, 1.29 times or 2.60 times that with Dy₂TmSbO₇, BiHoO₃ or nitrogen-doped TiO₂ (N-T). Therefore, the DBHP displayed higher photocatalytic activity for degrading the SMP under visible light irradiation compared with Dy₂TmSbO₇, BiHoO₃ or N-T. Specifically, the mineralization rate for removing the TOC concentration during the PADA process of the SMP with the DBHP was 1.18 times, 1.32 times or 2.79 times that with Dy₂TmSbO₇, BiHoO₃ or N-T. In addition, the stability and reusability of the DBHP were systematically evaluated, confirming that the DBHP owned potential applicability for degrading the antibiotic pollutant, which derived from the practical industrial wastewater. Trapping radicals experiments and the electron paramagnetic resonance measurement experiments were conducted for identifying the reactive radicals, such as the hydroxyl radicals (•OH), the superoxide anions (•O₂⁻) and the photogenerated holes (h⁺), which were generated with the DBHP for degrading the SMP during the PADA process under visible light irradiation, as a result, the •O₂⁻ possessed the maximal oxidative capability compared with the •OH or the h⁺. Above results indicated the degradation mechanism and the degradation pathways which were related to the SMP. In conclusion, this study makes a significant contribution for the development of the efficient Z-scheme heterostructure photocatalysts and provides a key opinion to the development of the sustainable remediation method with the view of mitigating the antibiotic pollution. Full article

The development of versatile photocatalysts is crucial for comprehensive solutions to the intertwined challenges of the energy crisis and environmental pollution. This study presents a novel Bi₃TiNbO₉/Bi₂MoO₆ (BTNO/BMO) heterojunction fabricated via a solvothermal method. Advanced characterization techniques verified the successful synthesis of the as-integrated BTNO/BMO heterostructure. The BTNO/BMO composite exhibited superior performance in multiple applications: efficient degradation of tetracycline reaching 90.2%, removal of gaseous nitric oxide (NO), and photocatalytic reduction of carbon dioxide (CO₂) to carbon monoxide (CO) with a yield of 51.3 μmol·g⁻¹. The constructed Type-II heterojunction demonstrated a remarkable ability to suppress charge recombination, thereby significantly enhancing the photocatalytic activity. This work highlights the dual-functional capability of the BTNO/BMO heterojunction for simultaneous environmental purification and fuel production, providing a promising material platform and a strategic design concept for sustainable technological development. Full article

Improving electronic and ionic transport and the structural stability of electrode materials is essential for the development of advanced lithium-ion batteries. Despite its great potential as a high-power anode, Ti₂Nb₁₀O₂₉ (TNO) still underperforms due to its unsatisfactory electronic and ionic conductivity. Here, a TNO/carbon microtube (TNO@CMT) composite is constructed via an ethanol-assisted solvothermal process and controlled annealing. The hollow carbon framework derived from kapok fibers provides a lightweight conductive skeleton and abundant nucleation sites for uniform TNO growth. By tuning precursor concentration, the interfacial structure and loading are precisely regulated, optimizing electron/ion transport. The optimized TNO@CMT-2 exhibits uniformly dispersed TNO nanoparticles anchored on both inner and outer CMT surfaces, enabling rapid electron transfer, short Li⁺ diffusion paths, and high structural stability. Consequently, it delivers a reversible capacity of 314.9 mAh g⁻¹ at 0.5 C, retains 75.8% capacity after 1000 cycles at 10 C, and maintains 147.96 mAh g⁻¹ at 40 C. Furthermore, the Li⁺ diffusion coefficient of TNO/CMT-2 is 5.4 × 10⁻¹¹ cm² s⁻¹, which is nearly four times higher than that of pure TNO. This work presents a promising approach to designing multi-cation oxide/carbon heterostructures that synergistically enhance charge and ion transport, offering valuable insights for next-generation high-rate lithium-ion batteries. Full article

Photoelectrochemical water splitting (PEC-WS) provides a sustainable route to transform solar energy into hydrogen; however, its overall efficiency is constrained by the inherently slow kinetics of the oxygen evolution reaction. Bismuth vanadate (BiVO₄) is considered an attractive visible-light-responsive photoanode due to its suitable band gap (~2.4 eV) and chemical stability; however, its efficiency is restricted by limited charge transport and significant charge carrier recombination. To overcome these limitations, BiVO₄–MoS₂ (BVO–MS) heterostructures were synthesized through a simple in situ hydrothermal approach, ensuring robust interfacial coupling and uniform dispersion of MS nanosheets over BVO dendritic surfaces. This intimate contact promotes rapid charge transfer and improved light-harvesting capability. Structural and spectroscopic analyses confirmed the formation of monoclinic BVO with uniformly integrated amorphous MS. The optimized BVO–MS10 electrode delivered a photocurrent density of 4.72 mA cm⁻² at 0.6 V vs. SCE, approximately 5.3 times higher than pristine BVO, and achieved an applied bias photon-to-current efficiency of 0.49%. Mott–Schottky analysis revealed a distinct negative shift in the flat-band potential for BVO–MS10, indicative of an upward movement of its conduction band and the establishment of a strong internal electric field that enhances charge separation and interfacial electron transport. These synergistic effects collectively endow the in situ engineered BVO–MS heterostructure with superior PEC water oxidation performance and highlight its promise for efficient solar-driven hydrogen generation. Full article

We report a fully biogenic route to ZnO, Fe₃O₄, and their hydrothermally coupled ZnO/Fe₃O₄ heterostructure and establish a synthesis–structure–function link. Phase-pure, quasi-spherical wurtzite ZnO and finer inverse-spinel Fe₃O₄ nanoparticles assemble into a biphasic interface without forming a solid solution; optical analysis yields E_g = 2.36 eV (ZnO), 1.46 eV (Fe₃O₄), and 1.45 eV (ZnO/Fe₃O₄), while PL shows near-band-edge quenching and green–yellow defect reweighting at 490–560 nm, consistent with interfacial band bending. Magnetically, ZnO/Fe₃O₄ is soft-ferrimagnetic with M_S/M_R/H_C = 226 emu g⁻¹/17 emu g⁻¹/0.010 T (at 300 K), enabling rapid magnetic recovery. Under natural sunlight (572.6 ± 32 W m⁻²), adsorption-corrected methylene blue removal (10 mg L⁻¹; 10 mg in 50 mL) gives real degradation rates RDR = 90% (ZnO), 65% (ZnO/Fe₃O₄), and 30% (Fe₃O₄) at 180 min, with pseudo–first-order constants k = 1.9 × 10⁻², 0.7 × 10⁻², and 0.4 × 10⁻² min⁻¹, respectively; dark adsorption baselines are 10%, 14%, and 49%. Reusability over four cycles preserves pseudo-first-order kinetics (ZnO/Fe₃O₄: 65% → 50%). Scavenger tests implicate ${}^{•}\mathrm{O}\mathrm{H}$ as the dominant oxidant in ZnO and ZnO/Fe₃O₄, and ${}^{•}\mathrm{O}_2^{-}$ in Fe₃O₄. Taken together, the band alignment, photoluminescence quenching, radical-scavenger profiles, and kinetic synergy are consistent with a defect-rich S/Z-scheme-like ZnO/Fe₃O₄ heterojunction, delivering a green, sunlight-operable, and recyclable platform for affordable wastewater remediation. Full article

Wide band gap (WBG) oxide and metal nanocomposites can possess bifunctionality from combining tightly coupled nanoobjects with different physicochemical properties. Adjusting synthesis conditions tunes these properties through modulating the process–morphology–function relationship. However, the controllable synthesis of such nanocomposites and their related applications are still underexplored. Here, we present a novel process flow to synthesize crystalline ZnO nanosheaves dotted with silver nanoparticles. The uniqueness of our strategy lies in the use of a silver mask for vertical growth of ZnO nanosheaves and thermal evaporating/dewetting Ag film to form a photocatalytic/plasmonic heterostructure. Upon combining a huge specific surface area and nanocrystallinity of ZnO nanosheaves, we enabled its surface-enhanced Raman scattering (SERS)-activity free of plasmonic components, yet their Ag modification resulted in improving detection limit in relation to Ellman’s reagent. Ag/ZnO nanosheaves showed dramatic photocatalytic activity to clean SERS-active surface. The systematic approach to synthesize Ag/ZnO heterostructure holds great promise in practical applications associated with interest in both photocatalytic and plasmonic properties. Full article

The photo-Fenton process is an advanced oxidation method widely employed in environmental remediation. Herein, we developed a novel metal–organic framework@hydrogen-bonded organic framework (MOF/HOF) composite with excellent photo-Fenton-like activity for the efficient degradation of organic dye methylene blue (MB). Cu-based MOF (CuBTC) was firstly prepared via the solvothermal method, then melamine (MA) and trimesic acid (TMA)-based HOF (MA-TMA) was grown in situ on CuBTC with hydrogen bonding interactions to produce the MOF/HOF composite CuBTC-MA. The CuBTC-MA composite could catalyze H₂O₂ to produce active substances for efficient MB degradation. The degradation rate constant of the CuBTC-MA composite was 4.4 times and 16.7 times higher than that of CuBTC and MA-TMA. The remarkably enhanced performance was attributed to the synergistic effect between the efficient separation of electron–holes supported by the type-II heterojunction structure of the CuBTC-MA composite and the Cu(I)/Cu(II) inter-conversion. The CuBTC-MA composite demonstrated exceptional repeatability and maintained a stable performance across a broad pH range. This study provided a novel paradigm for engineering heterogeneous MOF/HOF heterostructures, demonstrating significant potential in advancing photo-Fenton-like catalytic systems for the efficient environmental remediation of organic pollutants through synergistic charge separation and radical generation mechanisms. Full article

The development of advanced semiconductor-based catalysts for the rapid degradation of emerging pharmaceutical pollutants in water remains a critical challenge in environmental science. In this study, we present the synthesis, characterization, and catalytic performance of zinc oxide (ZnO) microtetrapods decorated with plasmonic Ag nanoparticles. These microtetrapods have been designed to enhance piezo-, photo-, and piezo-photocatalytic degradation of metronidazole (MNZ), a persistent antibiotic contaminant. ZnO microtetrapods were synthesized by high-temperature pyrolysis and using atmospheric-pressure microwave nitrogen plasma, followed by photochemical deposition of Ag nanoparticles at various precursor concentrations (0–1 mmol AgNO₃). The structural integrity of the samples was confirmed through X-ray diffraction (XRD) analysis, while the morphology was examined using scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). Additionally, spectroscopic analysis, including Raman, electron paramagnetic resonance (EPR), and photoluminescence (PL) spectroscopy, was conducted to verify the successful formation of heterostructures with adjustable surface loading of Ag. It has been shown that ZnO microtetrapods decorated with plasmonic Ag nanoparticles exhibit Raman-active properties. A systematic evaluation under photocatalytic, piezocatalytic, and combined piezo-photocatalytic conditions revealed a pronounced volcano-type dependence of catalytic activity on Ag content, with the 0.75 mmol composition exhibiting optimal performance. In the presence of both light irradiation and ultrasonication, the optimized Ag/ZnO composite exhibited 93% degradation of MNZ within a span of 5 min, accompanied by an apparent rate constant of 0.56 min⁻¹. This value stands as a significant improvement, surpassing the degradation rate of pristine ZnO by over 24-fold. The collective identification of defect modulation, plasmon-induced charge separation, and piezoelectric polarization as the predominant mechanisms driving enhanced reactive oxygen species (ROS) generation is a significant advancement in the field. These findings underscore the synergistic interplay between plasmonic and piezoelectric effects in oxide-based heterostructures and present a promising strategy for the efficient removal of recalcitrant water pollutants using multi-field activated catalysis. Full article