Photocatalytic Applications Research Articles

Lithium manganite anchored on mesoporous ceria photocatalyst for removal of Hg(II) ions from aqueous solution under visible illumination

The development of effective photocatalysts is critical for the photo/redox reaction of noxious Hg(II) ions and Hgo in environmental engineering and purification. In this contribution, Li2MnO3 nanoparticles (NPs) were anchored mesoporous CeO2 networks to design photocatalysts with high harvest of visible light, and the obtained Li2MnO3/CeO2 nanocomposites were utilized for photoreduction of Hg(II) ions under visible illumination. The TEM and XRD results showed the formation of Li2MnO3 and CeO2 with the monoclinic and cubic fluorite structures, and the particle size is about 10–20 nm. The enhancement of light absorption of Li2MnO3/CeO2 nanocomposites could create considerable photoinduced carriers during the photocatalytic reactions. The incorporation of Li2MnO3 and CeO2 NPs demonstrated outstanding photocatalytic performance compared with pristine CeO2 NPs, and the optimum 9%Li2MnO3/CeO2 nanocomposite achieved 98 % of the reduction Hg(II) ability within 60 min. The rate constant for 9 % Li2MnO3/CeO2 photocatalyst is ∼ 6.47 and 3.85 times greater than Li2MnO3 and CeO2 NPs. The superior photocatalytic performance of Li2MnO3/CeO2 nanocomposites was ascribed to the efficient separation of photocarriers due to the formation of S-scheme heterojunction, the large surface area, and mesoporous structures. The obtained Li2MnO3/CeO2 nanocomposite was highly stable and efficient for the Hg(II) photoreduction runs up to five successive experiments under similar conditions. Moreover, the possible mechanism over heterojunctions Li2MnO3/CeO2 nanocomposites toward the reduction of Hg(II) ions is examined as well. The formation of S-scheme heterojunction photocatalyst provides better photocatalytic applications in terms of air purification, hydrogen production, and water treatment.

An Old Material for a New World: Prussian Blue and Its Analogues as Catalysts for Modern Needs

Prussian blue analogues (PBAs) have recently emerged as effective materials in different functional applications, ranging from energy storage to electrochemical water splitting, thence to more “traditional” heterogeneous catalysis. Their versatility is due to their open framework, compositional variety, and fast and efficient internal charge exchange, coupled with a self-healing ability that makes them unique. This review paper presents and discusses the findings of the last decade in the field of the catalytic and photocatalytic application of PBAs in water remediation (via the degradation of organic pollutants and heavy metal removal) and the catalytic oxidation of organics and production or organic intermediates for industrial synthesis. Analysis of the catalytic processes is approached from a critical perspective, highlighting both the achievements of the research community and the limits still affecting this field.

Preparation and performance study of Mn-doped TiO2-loaded kapok-based activated carbon fibers

Due to its various advantages, such as a large specific surface area, high adsorption capacity, rapid adsorption rate, and moderate pore size, activated carbon fiber (ACF) has been extensively employed in wastewater treatment. In this study, the sol–gel-adsorption method was utilized to effectively synthesize Mn-doped TiO2-loaded kapok-based activated carbon fibers (Mn-TiO2/ACF). Several characterization techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and nitrogen adsorption-desorption were employed to investigate the Mn-TiO2/ACFs. The resulting Mn-TiO2/ACFs exhibited a combination of anatase and rutile forms in the produced TiO2. The introduction of Mn doping was found to hinder the crystal development, agglomeration, and crystallization of TiO2. The Mn-doped TiO2/ACFs demonstrated significant visible-light photocatalytic activity, attributed to the synergistic effects of two factors: the photocatalytic degradation of TiO2 films and the absorption capacity of ACF. The optimal molar ratio (Mn: Ti) for Mn-TiO2/ACFs in visible-light photocatalytic applications was determined to be 1:150. A pseudo-second-order kinetics model was employed to investigate the adsorption process of methyl bromide on Mn-TiO2/ACFs samples. The experimental results indicated that Mn-TiO2/ACF was reusable, with a removal efficiency exceeding 53% for all five cycles.

Exploring the semiconductor characteristics of a polyoxometalate-based organic-inorganic hybrid dimer and its photocatalytic applications

Polyoxometalate-based organic-inorganic hybrid compounds have been widely used in the field of photocatalysis, photoelectrocatalysis, interfacial materials of semiconductor device. However, their intrinsic semiconductor characteristics such as carrier diffusion lengths and carrier mobility are still unclear. Herein, we first unravel the carriers diffusion length and carrier mobility of the novel POM-based dimeric compound, {(HBW12O40)[Cu(2,2′-bipy)2]2[CuO(2,2′-bipy)(H2O)]}2·2H2O (1), which is successfully synthesized through co-assembly of binuclear Cu(II)-complex and BW12 in hydrothermal reaction. Space charge-limited currents (SCLC) method shows that the holes carriers mobility (μh) of this compound reached 0.84 cm2V−1s−1, which is more 30 times than that of raw BW12 (2.6 × 10−2 cm2V−1s−1). The calculated carrier diffusion lengths of compound 1 is 82 nm, which is almost 3 time higher than that of BW12 (25 nm), indicating that photogenerated carriers are more easily separated and diffused in compound 1. Furthermore, the semiconductor properties of compound 1 have been demonstrated by the measurements of photocurrent response, VB-XPS spectrum and band gap (Eg) values. In addition, its applications of photocatalysis indicate the excellent activities of compound 1 with 71 % degradation rate for photodegradation of methylene blue (MB) and 67 % degradation rate for photocatalytic reduction of Cr(VI).

Multicolor lignin-derived carbon quantum dots: Controllable synthesis and photocatalytic applications

The cost-effective, high-performance fabrication of multicolor carbon quantum dots (CQDs) from biomass is critical to its prospective application. Lignin, with its phenylpropane structural unit and abundant functional groups, is a reliable precursor for the formation of high-quality CQDs. Here, CQDs from renewable lignin were successfully prepared via a two-step method, and controllable preparation of CQDs to emit blue, green, yellow, and red fluorescence was achieved by adjusting the N-containing acid dopant. The investigated fluorescence mechanism revealed that the energy bandgap of the lignin-derived CQDs decreased and the emission wavelength redshifted as the graphitization degree and number of C=O surface groups increased. The light absorption region of the Bi7O9I3 photocatalysts modified with blue CQDs to red CQDs gradually broadened in the redshifted direction. In particular, compared with pure Bi7O9I3 (70.9%), the red CQDs-modified Bi7O9I3 (RCQD/BOI) can remove 94.7% of antibiotics within 60 min of light irradiation. The superior photocatalytic activity of RCQD/BOI is attributed to the established internal electric field that accelerates charge transfer and effectively separates the photogenerated e+-h+ inside Bi7O9I3. Furthermore, through radical capture, electron paramagnetic resonance (EPR) experiments validated the photocatalytic mechanism of RCQD/BOI and revealed that h+, O2− and OH are key reactants in the photocatalytic degradation process. This promising and sustainable approach for the synthesis of multicolor lignin-derived CQDs opens the avenue of high-value utilization of biomass resources, green production of CQDs nanomaterials, and efficient development of CQDs-based photocatalysts for wastewater treatment.

Elucidating Solvatochromic Shifts in Two-Dimensional Photocatalysts by Solving the Bethe-Salpeter Equation Coupled with Implicit Solvation Method.

Many studies have focused on tailoring the photophysical properties of two-dimensional (2D) materials for photocatalytic (PC) or photoelectrochemical (PEC) applications. To understand the optical properties of 2D materials in solution, we established a computational method that combined the Bethe-Salpeter equation (BSE) calculations with our GW-GPE method, allowing for GW/BSE-level calculations with implicit solvation described using the generalized Poisson equation (GPE). We applied this method to MoS2, phosphorene (PP), and g-C3N4 and found that when the solvent dielectric increased, it reduced the exciton binding energy and quasiparticle bandgap, resulting in almost no solvatochromic shift in the excitonic peaks of MoS2 and PP, which is consistent with previous experiments. However, our calculations predicted that the solvent dielectric had a significant impact on the excitonic properties of g-C3N4, exhibiting a large solvatochromic shift. We expect that our GW/BSE-GPE method will offer insights into the design of 2D materials for PC and PEC applications.

Lead-Free Semiconductors: Phase-Evolution and Superior Stability of Multinary Tin Chalcohalides.

Tin-based semiconductors are highly desirable materials for energy applications due to their low toxicity and biocompatibility relative to analogous lead-based semiconductors. In particular, tin-based chalcohalides possess optoelectronic properties that are ideal for photovoltaic and photocatalytic applications. In addition, they are believed to benefit from increased stability compared with halide perovskites. However, to fully realize their potential, it is first necessary to better understand and predict the synthesis and phase evolution of these complex materials. Here, we describe a versatile solution-phase method for the preparation of the multinary tin chalcohalide semiconductors Sn2SbS2I3, Sn2BiS2I3, Sn2BiSI5, and Sn2SI2. We demonstrate how certain thiocyanate precursors are selective toward the synthesis of chalcohalides, thus preventing the formation of binary and other lower order impurities rather than the preferred multinary compositions. Critically, we utilized 119Sn ssNMR spectroscopy to further assess the phase purity of these materials. Further, we validate that the tin chalcohalides exhibit excellent water stability under ambient conditions, as well as remarkable resistance to heat over time compared to halide perovskites. Together, this work enables the isolation of lead-free, stable, direct band gap chalcohalide compositions that will help engineer more stable and biocompatible semiconductors and devices.

A novel g-C3N4-SH@konjac glucomannan composite aerogel for patulin removal from apple juice and its photocatalytic regeneration

Patulin (PAT) is a hazardous mycotoxin frequently occurs in fruit industry. A reusable g-C3N4-SH@KG composite aerogel for PAT removal in a novel “dark adsorption-light regeneration” mode was prepared by thiol(-SH) functionalization and konjac glucomannan (KG) immobilization. The g-C3N4-SH@KG was characterized by SEM, FT-IR, XPS and UV–Vis DRS, and its PAT adsorption and photocatalytic regeneration behaviors and mechanisms were investigated. The g-C3N4-SH@KG exhibited good regeneration performance, maintaining 83% of PAT initial adsorption capacity (0.92 mg/g) after 5 “adsorption-regeneration” cycles. The adsorption process was endothermic and spontaneous. •OH and h+ generated by photocatalysis were the main substances that degraded PAT into two products and regenerated -SH. The g-C3N4-SH@KG could effectively remove PAT without negative impact on juice quality. The study provided a new strategy for the regeneration of thiol-functionalized PAT adsorbents, and a new idea for the application of non-selective photocatalysis in the control of food contaminations.

Influence of Composition and Structure on the Optoelectronic Properties of Photocatalytic Bi4NbO8Cl-Bi2GdO4Cl Intergrowths.

Mixed metal oxyhalides are an exciting class of photocatalysts, capable of the sustainable generation of fuels and remediation of pollutants with solar energy. Bismuth oxyhalides of the types Bi4MO8X (M = Nb and Ta; X = Cl and Br) and Bi2AO4X (A = most lanthanides; X = Cl, Br, and I) have an electronic structure that imparts photostability, as their valence band maxima (VBM) are composed of O 2p orbitals rather than X np orbitals that typify many other bismuth oxyhalides. Here, flux-based synthesis of intergrowth Bi4NbO8Cl-Bi2GdO4Cl is reported, testing the hypothesis that both intergrowth stoichiometry and M identity serve as levers toward tunable optoelectronic properties. X-ray scattering and atomically resolved electron microscopy verify intergrowth formation. Facile manipulation of the Bi4NbO8Cl-to-Bi2GdO4Cl ratio is achieved with the specific ratio influencing both the crystal and electronic structures of the intergrowths. This compositional flexibility and crystal structure engineering can be leveraged for photocatalytic applications, with comparisons to the previously reported Bi4TaO8Cl-Bi2GdO4Cl intergrowth revealing how subtle structural and compositional features can impact photocatalytic materials.

Tunable Electronic and Optical Properties of MoGe2N4/AlN and MoSiGeN4/AlN van der Waals Heterostructures toward Optoelectronic and Photocatalytic Applications

Tunable Electronic and Optical Properties of MoGe2N4/AlN and MoSiGeN4/AlN van der Waals Heterostructures toward Optoelectronic and Photocatalytic Applications

Charge Transfer from Quantum-Confined 0D, 1D, and 2D Nanocrystals.

The properties of colloidal quantum-confined semiconductor nanocrystals (NCs), including zero-dimensional (0D) quantum dots, 1D nanorods, 2D nanoplatelets, and their heterostructures, can be tuned through their size, dimensionality, and material composition. In their photovoltaic and photocatalytic applications, a key step is to generate spatially separated and long-lived electrons and holes by interfacial charge transfer. These charge transfer properties have been extensively studied recently, which is the subject of this Review. The Review starts with a summary of the electronic structure and optical properties of 0D-2D nanocrystals, followed by the advances in wave function engineering, a novel way to control the spatial distribution of electrons and holes, through their size, dimension, and composition. It discusses the dependence of NC charge transfer on various parameters and the development of the Auger-assisted charge transfer model. Recent advances in understanding multiple exciton generation, decay, and dissociation are also discussed, with an emphasis on multiple carrier transfer. Finally, the applications of nanocrystal-based systems for photocatalysis are reviewed, focusing on the photodriven charge separation and recombination processes that dictate the function and performance of these materials. The Review ends with a summary and outlook of key remaining challenges and promising future directions in the field.

Optoelectronic properties and charge transfer dynamics in graphene quantum dot/Ir(III) nanocomposites: Enhancing photocatalytic performance through strategic BTF conjugate binding and end-capping variations

The aim of this study is to analyze the optoelectronic properties and charge transfer kinetics in nanocomposites comprising graphene quantum dots (GQDs) and Ir(III) complexes, with a specific focus on their relevance in photocatalytic applications. The investigation explores how the extent of π-conjugation, variations in end-capping substituents, and the binding position of benzothiazole fluorene (BTF) conjugates influence the electronic structures. The results indicate that attaching GQDs alters the band gaps and results in different energy alignments. By adjusting the position of BTF conjugate binding and the end-capping substituent, optimal photocatalytic performance can be achieved. Binding the BTF conjugate at the para-position enhances electron injection into TiO2, thereby improving photocatalysis. Conversely, binding the BTF at the meta-position contributes to the regeneration of the ground state, leading to increased light absorption and photoelectric conversion. Furthermore, incorporating a BTF conjugate at the meta-position of the 2-phenyl pyridine ligand enhances light absorption and photoelectric conversion in the nanocomposites. These findings pave the way for further exploration of the effects of different conjugate binding positions and substituents on the overall properties and potential applications of these nanocomposites.

Metal-Organic Frameworks-Derived Nanocarbon Materials and Nanometal Oxides for Photocatalytic Applications.

Harnessing low-density solar energy and converting it into high-density chemical energy through photocatalysis has emerged as a promising avenue for the production of chemicals and remediation of environmental pollution, which contributes to alleviating the overreliance on fossil fuels. In recent years, metal-organic frameworks (MOFs) have gained widespread application in the field of photocatalysis due to their photostability, tunable structures, and responsiveness in the visible light range. However, most MOFs exhibit relatively low response to light, limiting their practical applications. MOFs-derived nanomaterials not only retain the inherent advantages of pristine MOFs but also show enhanced light adsorption and responsiveness. This review categorizes and summarizes MOFs-derived nanomaterials, including nanocarbons and nanometal oxides, providing representative examples for the synthetic strategies of each category. Subsequently, the recent research progress on MOFs-derived materials in photocatalytic applications are systematically introduced, specifically in the areas of photocatalytic water splitting to H2, photocatalytic CO2 reduction, and photocatalytic water treatment. The corresponding mechanisms involved in each photocatalytic reaction are elaborated in detail. Finally, the review discusses the challenges and further directions faced by MOFs-derived nanomaterials in the field of photocatalysis, highlighting their potential role in advancing sustainable energy production and environmental remediation.

Synthesis and Characterization of Superhydrophobic Epoxy Resin Coating with SiO2@CuO/HDTMS for Enhanced Self-Cleaning, Photocatalytic, and Corrosion-Resistant Properties.

The exceptional corrosion resistance and combined physical and chemical self-cleaning capabilities of superhydrophobic photocatalytic coatings have sparked significant interest among researchers. In this paper, we propose an economical and eco-friendly superhydrophobic epoxy resin coating that incorporates SiO2@CuO/HDTMS nanoparticles modified with Hexadecyltrimethoxysilane (HDTMS). The application of superhydrophobic coatings effectively reduces the contact area between the metal surface and corrosive media, leading to a decreased corrosion rate. Additionally, the incorporation of nanomaterials, exemplified by SiO2@CuO core-shell nanoparticles, improves the adhesion and durability of the coatings on aluminum alloy substrates. Experimental data from Tafel curve analysis and electrochemical impedance spectroscopy (EIS) confirm the superior corrosion resistance of the superhydrophobic modified aluminum alloy surface compared to untreated surfaces. Estimations indicate a significant reduction in corrosion rate after superhydrophobic treatment. Furthermore, an optical absorption spectra analysis of the core-shell nanoparticles demonstrates their suitability for photocatalytic applications, showcasing their potential contribution to enhancing the overall performance of the coated surfaces. This research underscores the promising approach of combining superhydrophobic properties with photocatalytic capabilities to develop advanced surface modification techniques for enhanced corrosion resistance and functional properties in diverse industrial settings.

Effect of Photocatalytic Pretreatment on the Membrane Performance in Nanofiltration of Textile Wastewater

Traditional methods like biological treatment, flocculation-coagulation, adsorption, and advanced oxidation are commonly employed for textile wastewater treatment, but their sustainability is hindered by issues such as the adverse impact of textile wastewater on microorganisms and the requirement for substantial chemical usage. In response to increasingly stringent legal discharge standards, membrane technologies are emerging as prominent alternatives for effective textile wastewater treatment. The application of photocatalysis as a pretreatment to improve effluent quality and treatment performance has shown effective results in the treatment of textile wastewater by nanofiltration (NF). However, innovative solutions are needed to improve the efficiency of UV photocatalytic reactors. Here, the TiO2/halloysite nanotube (HNT) photocatalyst was shown to completely remove dyes under UV illumination. Two wastewater samples from photocatalytic (PC) pretreatment were treated using innovative NF membranes with different contents. The study examined the impact of PC pretreatment on the flux of wastewater from a textile factory heat recovery tank, which increased from 18.32 to 27.63 L/m2.h. The membranes achieved > 98% removal in COD, while bare membrane achieved 95% removal in conductivity. The addition of s-DADPS as monomer and HNT as nanoparticles to the membranes with different compositions affected the cross-linking in the TFC layer. During the tests conducted on the water extracted from the dyeing tank, the color was completely eliminated without any loss of flux. Additionally, improvements in COD removal were observed.

Facile synthesis of bulk Au-Co-CoOx-CeOx@iron ball and its photocatalytic application in 4-nitrophenol degradation

Bulk noble metal–semiconductor composites can be chosen as photocatalysts to carry out the flow degradation of 4-nitrophenol (4-NP) whereas their preparation is complex and uncontrollable. Here, bulk Au-Co-CoOx-CeOx@iron ball (Au/Co-CC@iron ball) is designed and prepared by a facile and controllable route without any toxic chemical. The bulk Au/Co-CC@iron ball shows excellent photocatalytic activity and reusability for the 4-NP degradation, which can be ascribed to the synergistic action of active components and foliated iron ball surface. Furthermore, the highly active Au/Co-CC@iron ball is used as packing material to construct a new-type of packed reactor, by which the flow degradation of 4-NP is successfully achieved. As-fabricated packed reactor and its tandem module exhibit superior photocatalytic performance for the flow degradation of 4-NP. Noteworthy, based on the tandem module with six reactors, the removal rate of 4-NP can reach up to 2750 µmol/h. Meanwhile, the reactor and its module display satisfactory operational stability and reusability in the flow degradation of 4-NP. Clearly, the provided route is effective for the preparation of bulk noble metal–semiconductor composites with exceptional performance, which can also be a prospective strategy to obtain bulk packing materials to serve for the flow degradation.

Harnessing Pb-S Interactions for Long-Term Water Stability in Cesium Lead Halide Perovskite Nanocrystals.

Lead halide perovskite nanocrystals (LHP NCs) have garnered attention as promising light-harvesting materials for optoelectronics and photovoltaic devices, attributed to their impressive optoelectronic properties. However, their susceptibility to moisture-induced degradation has hindered their practical applications. Despite various encapsulation strategies, challenges persist in maintaining their stability and optoelectronic performance simultaneously. Here, a ligand exchange approach is proposed using (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide (MUTAB) to enhance the stability and dispersibility of CsPbBr3 (CPB) NCs in aqueous environments. MUTAB enables effective surface passivation of the CPB NCs via robust Pb-S interactions at the S-terminal while concurrently directing water molecules through the unbound cationic N-terminal or vice versa, ensuring water dispersibility and stability. Spectroscopic analysis confirms retained structural and optical integrity post-ligand exchange. Crucially, MUTAB-bound CPB NCs exhibit sustained charge transfer properties, demonstrated by aqueous colloidal oxidation reactions. This ligand exchange strategy offers a promising pathway for advancing LHP NCs toward practical optoelectronic and photocatalytic applications.

Vinyl-Group-Anchored Covalent Organic Framework for Promoting the Photocatalytic Generation of Hydrogen Peroxide.

The artificial photosynthesis of H2O2 from water and oxygen using semiconductor photocatalysts is attracting increasing levels of attention owing to its green, environmentally friendly, and energy-saving characteristics. Although covalent organic frameworks (COFs) are promising materials for promoting photocatalytic H2O2 production owing to their structural and functional diversity, they typically suffer from low charge-generation and -transfer efficiencies as well as rapid charge recombination, which restricts their use as catalysts for photocatalytic H2O2 production. Herein, we report a strategy for anchoring vinyl moieties to a COF skeleton to facilitate charge separation and migration, thereby promoting photocatalytic H2O2 generation. This vinyl-group-bearing COF photocatalyst exhibits a H2O2-production rate of 84.5 μmol h-1 (per 10 mg), which is ten-times higher than that of the analog devoid of vinyl functionality and superior to most reported COF photocatalysts. Both experimental and theoretical studies provide deep insight into the origin of the improved photocatalytic performance. These findings are expected to facilitate the rational design and modification of organic semiconductors for use in photocatalytic applications.

Vinyl‐Group‐Anchored Covalent Organic Framework for Promoting the Photocatalytic Generation of Hydrogen Peroxide

AbstractThe artificial photosynthesis of H2O2 from water and oxygen using semiconductor photocatalysts is attracting increasing levels of attention owing to its green, environmentally friendly, and energy‐saving characteristics. Although covalent organic frameworks (COFs) are promising materials for promoting photocatalytic H2O2 production owing to their structural and functional diversity, they typically suffer from low charge‐generation and ‐transfer efficiencies as well as rapid charge recombination, which restricts their use as catalysts for photocatalytic H2O2 production. Herein, we report a strategy for anchoring vinyl moieties to a COF skeleton to facilitate charge separation and migration, thereby promoting photocatalytic H2O2 generation. This vinyl‐group‐bearing COF photocatalyst exhibits a H2O2‐production rate of 84.5 μmol h−1 (per 10 mg), which is ten‐times higher than that of the analog devoid of vinyl functionality and superior to most reported COF photocatalysts. Both experimental and theoretical studies provide deep insight into the origin of the improved photocatalytic performance. These findings are expected to facilitate the rational design and modification of organic semiconductors for use in photocatalytic applications.

Template assisted sol-gel synthesis of BiFeO3 hollow tubes: Introducing kapok fiber as a bio-template

Bismuth ferrite (BiFeO3) is a perovskite material well known for its multifunctional properties and related applications. The recent research on this material includes the synthesis of hollow-structured BiFeO3 using various methods and exploring their applications in photocatalysis and sensing. Here, we introduce a facile method for the synthesis of BiFeO3 hollow tubes using the sol-gel method, where kapok fiber collected from Ceiba pentandra is used as a biotemplate for the first time. In the procedure, the annealing path was modified by introducing intermediate holding steps besides varying the final annealing temperature. The structural analysis was carried out using X-ray diffraction (XRD) and Raman analysis, whereas the formation of hollow tube morphology was confirmed with the help of FESEM analysis. The complete decomposition of the kapok fiber template during the annealing process was confirmed with the help of Fourier transform infrared spectroscopy. The XRD analysis indicated that monitoring both the annealing pathway and the final annealing temperature is pivotal in attaining the formation of phase pure BiFeO3. The proposed method eliminates the requirement for additional procedures for extracting the synthesized hollow tubes from the parent template, in addition to providing a less expensive strategy for the synthesis of BiFeO3 hollow tubes.