Self-template Approach Research Articles

A controllable self-template synthesis strategy for hierarchical porous carbon microspheres with cavity structures for supercapacitor applications

Herein, we introduce a novel and controllable self-template approach for fabricating hierarchical porous carbon microspheres with cavities (CPCMs). This approach uses polyacrylonitrile (PAN) and acrylamide (AM) microspheres as templates, which feature small anisotropic bumps on their surface. These bumps are encapsulated by divinylbenzene (DVB) during the coating polymerization process. The subsequent hydrolysis of PAN and AM led to the formation of a hierarchical porous structure. Specifically, mesopores mainly arose from PAN hydrolysis, whereas AM contributed additional micropores and macropores, generating an intricate pore structure within the DVB shell. This method differs from traditional pore-making approaches. Additionally, in situ doping of nitrogen (N) and oxygen (O) atoms was achieved. The amount of DVB coating can be adjusted to vary the shell thickness, allowing for the modulation of the pore size distribution and surface micromorphology. Owing to the synergistic effects of an ultrahigh specific surface area (1151.9 m2 g−1), extensive pore volume (1.2575 m3 g−1), and well-structured micro-meso-macropore hierarchy, along with N/O codoping, the resulting carbon material exhibited outstanding electrochemical energy storage performance. Notably, the optimal CPCMs-2 electrode achieves an exceptional specific capacitance of 377 F g−1 at a current density of 0.5 A g−1. This study proposes a novel avenue for designing hierarchical porous carbon materials, and CPCMs could be expanded to a wide range of applications.

Single-step template-free synthesis of fluoro-functionalized covalent organic frameworks with a tunable hollow structure for extraction of phthalate acid esters from human urine

Phthalate acid esters (PAEs) are recognized as endocrine disruptors, exhibit carcinogenic characteristics, and have the potential to impair fertility, thereby posing significant risks to both the environment and human health. Consequently, biomonitoring and exposure assessment of PAEs are of paramount importance. Presently, the majority of detection methods for PAEs are centered on aqueous matrices, and the development of techniques for the identification of PAEs in complex matrices remains an area of active research. This paper designed and synthesized a novel fluoro-functionalized hollow covalent organic framework (F-HCOF), characterized by a tunable hollow spherical structure and enriched with fluorine functional groups, through a one-step self-template approach, which effectively regulated the formation of the hollow structure. The synthesized F-HCOF with tunable hollow structures and abundant F functional groups provided efficient diffusion pathways and adsorption sites, facilitating robust and selective adsorption of the target PAEs. Using F-HCOF as a coating, a solid-phase microextraction method was developed to extract PAEs from complex matrices. The method exhibited limits of detection ranging from 0.0108 to 0.0581 ng L−1, with enrichment factors spanning from 2535.3 to 8985.3. The self-made F-HCOF fibers demonstrated the capability to effectively enrich PAEs under various interference conditions, further verifying their feasibility for practical sample analysis. This work provided a strategic approach for the synthesis of F-functionalized hollow COF adsorbents and explored the formation process of hollow spheres. It enables matrix interference-resistant analysis of PAEs, and offers a practical method for studying PAEs exposure and metabolism within the human body.

COF-derived porous nitrogen-doped carbon for removal of emerging organic contaminants and efficient uranium extraction from seawater

The development of adsorbents for efficient and highly selective seawater extraction of uranium was instrumental in fostering sustainable progress in energy and addressing the prevailing energy crisis. However, the complex background composition of the marine environment, including radionuclides, organic pollutants, and a large number of co-existing heavy metal ions, were non-negligible obstacles to the extraction of uranium from seawater. The present investigation successfully employed a self-templated approach to synthesize porous nitrogen-doped carbon (PNC) derived from COF, which exhibited tremendous potential as an adsorbent for pollutant removal in environmental treatment. LZU1@PNC not only retained the structural features of the original COF-LZU1, but also overcame the acid-base instability problem commonly found in COFs. Subsequently, the removal process of two typical water pollutants on the material was investigated using 2,4-DCP and [UO2(CO3)3]4-. The results demonstrated that LZU1@PNC exhibited superior removal performance for the target pollutants compared to COF-LZU1, owing to its larger specific surface area and abundant defect structure. After six desorption-regeneration cycles, LZU1@PNC still maintained a high removal rate of the target contaminants, demonstrating the stability of this material and its excellent recyclability. In addition, based on various characterization techniques, the removal mechanism of 2,4-DCP was presumed to be mainly electrostatic attraction, hydrogen bonding, and π-π stacking interactions. Conversely, the elimination process of [UO2(CO3)3]4- predominantly relied on surface complexation phenomena. The present investigation provided new perspectives and stimulated a broader study of other COF-derived carbon materials and their modifications as adsorbents for uranium extraction from seawater and other applications.

The synthesis of multi-level porous MOF composite materials with different MOF contents

To address the inherent limitations of current MOF synthesis, where pore size is restricted to micropores or small mesopores, we successfully synthesized MOF composite materials with well-developed porous structures using a self-template approach. These pores encompass not only the intrinsic micropores or small mesopores of MOFs but also the template-induced large pores. During the experimental process, we achieved the synthesis of composite materials with varying MOF contents by modifying experimental conditions. Through this design, we not only achieved selective adsorption of guest molecules but also significantly increased the porosity, thereby enhancing the mass transfer efficiency of guest molecules and the utilization rate of materials. This research breakthrough offers new insights and solutions for addressing critical issues in fields such as gas separation, energy storage, and catalysis.

Introduction of bimetallic oxide-modified carbon nanotubes for boosting the energy storage performance of NiCo-LDH based in-plane micro-supercapacitors on paper

In-plane micro-supercapacitors (IMSCs) have greater promise for use in flexible wearable electronics than traditional stacked configurations due to their ease of integration and conformability. Nickel-cobalt layered double hydroxide (NiCo-LDH) has garnered significant interest as a stellar material for supercapacitors because of its affordable price, regular morphology, and high theoretical capacity. Unfortunately, the intrinsic poor conductivity of LDH materials prevents supercapacitors from achieving long-term stable cycling and the desired energy density. This research successfully applies the self-templated approach to prepare carbon nanotubes (CNTs) with heterogeneous architectures and numerous phase interfaces, thereby mitigating this disadvantage. Carbon nanosheets adorned with WO2 and MoO2 nanoparticles assemble the CNT with a typical three-dimensional structure. When combined with LDH in a suitable ratio, the composite electrode’s conductivity significantly improves, providing increased capacity and cycling stability. Compared to commercial CNTs, the larger size of the prepared WO2/MoO2@P, N-CNTs serves a superior supporting and connecting role, thereby preventing the NiCo-LDH from aggregating. Under the best conditions, the composite electrode demonstrates a capacity of 1237 C/g at 1 A g−1 and an optimal capacity retention of more than 92%. For the IMSC devices, the composite materials as the positive electrode achieve an energy density of 0.0590 mWh cm−2, and no capacity degradation is observed after 10,000 cycles. In addition, bending tests have demonstrated the mechanical stability of the IMSCs. Therefore, this strategy of mixing highly conductive WO2/MoO2@P, N-CNTs can effectively improve the conductivity of the composite material and the mechanical properties of the overall device. Furthermore, this concept can be further extended to the preparation and application of other wearable devices.

Self-template synthesis of hollow flower-like NiCo2O4 nanoparticles as an efficient bifunctional catalyst for oxygen reduction and oxygen evolution in alkaline media

Abstract A method was proposed to synthesize hollow flower-like NiCo2O4 composed of porous nanosheets using a self-template approach. The unique structure is attributed to the synergistic effect of the Kirkendall effect and the Ostwald ripening mechanism. The sheet-like and porous structure endowed the material with a specific surface area of 137.1 m2 g−1 and a pore volume of 0.418 cm3 g−1. The distinctive structure and high-density active sites imparted excellent catalytic performance in oxygen reduction (ORR) and oxygen evolution (OER) reactions. Electrochemical tests showed that the limit current density of ORR reached 5.58 mA cm−2, comparable to that of the noble metal Pt/C (20 wt%). The overpotential of OER at a current density of 10 mA cm−2 was only 380 mV, significantly lower than that of the noble metal RuO2. These results indicate that the synthesized hollow flower-like NiCo2O4 has the potential to replace noble metals in ORR and OER catalytic applications.

New high-entropy transition-metal sulfide nanoparticles for electrochemical oxygen evolution reaction

Developing extremely efficient electrocatalysts for oxygen evolution reactions (OER) is a decisive step toward the progression of rechargeable metal-oxygen batteries, CO2 reduction, and water-splitting. Nanoporous high-entropy transition-metal sulfides (np-HETMS) represent a new generation of promising OER catalysts by virtue of their exceptional catalytic activity. However, their synthesis maintains to be a challenge by reason of the thermodynamic immiscibility of the constituting multi-principal metallic elements in the sulfide structure. Herein, for the first time, the np-HETMS ((CoFeNiMnCu)S2) nanoparticles with pyrite-phase was synthesized via a facile and easy adaptable glycerol-assisted self-template approach to resolve the immiscibility of multi-metallic constituents. The coordination of metal ions with polyalcohol in metal glycerate, as an intermediate template, is beneficial for achieving atomic blending of multiple metal ions in sulfides structure at HETMSs during the synthesis procedure. In reliance on the electronic and physicochemical traits, the electronic configuration of as-synthesized (CoFeNiMnCu)S2 was elucidated by virtue of the comparison with its quaternary, ternary, and binary subsystems. The superior performance of np-HETMS (CoFeNiMnCu)S2 nanoparticles, corresponding subsystems, and commercial RuO2 catalyst are accentuated by integrating into a three-electrode configuration for OER reaction. The (CoFeNiMnCu)S2 nanoparticles exhibited a trivial overpotential of 284 mV when the current density reached 10 mA/cm2 with a low Tafel slope of 57 mV/dec in a 1.0 M KOH solution. Besides providing a novel and highly active high-entropy-based electrocatalyst, this work inaugurates a new synthesis paradigm toward high-entropy metal alloys for extremely efficient electrocatalysis applications.

Facile self-template synthesis of sulphur and nitrogen-codoped nanoporous carbon derived from functionalized polyethersulfone (PES) and its application for supercapacitors

• A self-template approach to prepare N and S co-doped porous carbon is proposed. • The SNC-800 shows a high specific capacitance (240F/g). • The device (SNC-800//SNC-800) exhibits superior supercapacitive behavior to many carbon materials. A Novel Sulphur and Nitrogen-codoped carbon (SNC-800) material was prepared by pyrolysis of functionalized Polyethersulfone (PES) under 800℃, which was synthesized by one-pot polymerization. The SNC-800 was served as electrode material and showed a high specific capacitance (240 F/g). The capacitance retention of SNC-800 is as high as 91.6% after 10,000 cycles. The device base on delivered a high energy density (23.5 Wh/kg) with power density (800 W/kg). These results suggest that SNC-800 is a promising electrode material for supercapacitors.

Multi-scale self-templating synthesis strategy of lignin-derived hierarchical porous carbons toward high-performance zinc ion hybrid supercapacitors

Chemical activation is a common process for preparing porous carbon electrode materials of supercapacitors. Nevertheless, chemical activation approach has the disadvantages of being chemically caustic, environmentally unfriendly, and expensive. This study constitutes a multi-scale self-template approach for the preparation of lignin-derived hierarchical porous carbons (LHPCs) with high specific surface areas and excellent electrochemical performances. KCl, carbonates, and sulfates, generated in the carbonization process, play the role of multi-scale template agents for the pore-forming process. LHPCs exhibited superb electrochemical performances as electrodes of supercapacitors with alkaline and neutral sulfate electrolytes. In addition, the Zn//LHPCs hybrid supercapacitors (ZIHSCs) achieved an ultra-high energy density of 135 Wh kg−1, which is 20 times higher than symmetric supercapacitors with KOH electrolytes (6.6 Wh kg−1) and 9 times higher than symmetric supercapacitors with Na2SO4 electrolyte (14.8 Wh kg−1). This work proposes a general multi-scale self-template strategy for the synthesis of hierarchical porous carbons from sodium lignosulfonate for supercapacitor applications.

Coordinated single-molecule micelles: a self-template approach for preparing mesoporous doped carbons.

Porous carbons prepared using a self-template approach inherit the pore features of template, but they exhibit almost no evenly dispersed mesopores, which is significant for diffusion-limited applications. Herein, N-doped hierarchically porous carbons (NHPCs) with uniform mesopores are prepared using a self-template method. The spherical single-molecule micelle of polystyrene-b-poly(4-vinyl pyridine) (PS-b-P4VP) is turned into a Zn2+-coordinated PS-b-P4VP micelle (CPM) by coordination of Zn2+ with the P4VP shell. Then, the self-template of the CPM is carbonized into a hollow carbon nanosphere. During carbonization, the PS core is decomposed to generate the central mesopore, whereas the Zn2+-coordinated P4VP shell is transformed into a carbonaceous shell. These even hollow carbon nanospheres aggregate to form uniformly mesoporous carbon lumps. Simultaneously, the coordinated Zn2+ of the CPM is reduced to metal zinc at high temperatures and then it is evaporated, thus creating numerous micropores in the carbonaceous shell. These NHPCs with uniform mesopores display a high specific surface area. As a demonstration in diffusion-limited applications, their catalytic performances for the oxygen reduction reaction (ORR) are investigated. Strikingly, NHPCs exhibit outstanding catalytic performances for the ORR. This self-template method paves a facile approach for preparing mesoporous carbons with high performances.

Carbon-incorporated Ni2P-Fe2P hollow nanorods as superior electrocatalysts for the oxygen evolution reaction.

A rational design and cost-effective transition metal-based hollow nanostructures are important for sustainable energy materials with high efficiency. This study reports on carbon-incorporated Ni2P-Fe2P hollow nanorods ((Ni,Fe)2P/C HNRs) derived from a self-template approach as efficient electrocatalysts. Initially, a Ni2(BDC)2(DABCO)-MOF (Ni-MOF) is converted to NiFe-PBA hollow nanorods (HNRs) through facile ion exchange which was further converted to (Ni,Fe)2P/C HNRs via a subsequent phosphidation process. The resulting (Ni,Fe)2P/C HNRs exhibit remarkable activity for the oxygen evolution reaction in an alkaline solution requiring a small overpotential of 258 mV to drive a current density of 10 mA cm-2 and long-term stability with little deactivation after 40 h. (Ni,Fe)2P/C HNRs outperform (Ni,Fe)2P/C NPs and commercial RuO2. The unique hollow morphology and interfacial electronic structure substantially increase the active site and charge transfer rate of our electrocatalyst, resulting in excellent OER activity and stability.

Self-templated formation and characterization of polyhedral CoS hollow nanocage (HNC) for heavy metal ions (Ag+, Cd2+, Cu2+, Pb2+ and Zn2+) removal in aqueous solutions

The contamination of water by heavy metal ions can easily cause serious environmental problems and damage to the human body hands down. Using zeolitic imidazolate framework-67 (ZIF-67) as a sacrificial template, polyhedral CoS hollow nanocages (HNC) were successfully synthesized by self-template approach as adsorbents for heavy metal ions removal. The CoS HNCs suggested good chemical stability and extremely efficient heavy metal ions removal of Ag+, Cd2+, Cu2+, Pb2+ and Zn2+, which can be ranked in the order of Ni2+ ≪ Zn2+, Cd2+ < Pb2+, Cu2+, Ag+. The saturation adsorption for Ag+ reached 2147.944 mg g−1 and exhibited high distribution coefficients (Kd) > 107 mL g−1. The CoS HNCs can rapidly reduce the Ag + concentration from ppm level to trace level of 1 ppb. It has been proved that the rapid and selective adsorption was achieved via the hierarchical pore structure of the CoS HNCs can better disperse these metal vacancies with super affinity and the S2−, reduce the mass transfer distance and accelerate mass transfer. It is expected that such a CoS HNCs could be a promising alternative to conventional materials for the adsorption of heavy metal ions.

One-dimensional cobalt oxide nanotubes with rich defect for oxygen evolution reaction

For the electrochemcial hydrogen production, the oxygen evolution reaction (OER) is a pivotal half-reaction in water splitting. However, OER suffers sluggish kinetics and high overpotential, leading to the increase of overall energy consumption and decrease of the energy efficiency. In this work, high-quality cobalt oxide porous nanotubes (Co3O4-PNTs) are easily obtained by simple self-template approach. One-dimensional (1D) porous structure provides the large specific surface area, enough abundant active atoms and effective mass transfer. In addition, Co3O4-PNTs also own self-stability of 1D architecture, benefitting the their durability for electrocatalytic reaction. Thus, Co3O4-PNTs with optimal annealing temperature and time reveal the attractive alkaline OER performance (Tafel slope of 56 mV dec−1 and 323 mV overpotential at 10 mA cm−2), which outperform the Co3O4 nanoparticles and benchmark commercial RuO2 nanoparticles. Furthermore, Co3O4-PNTs also exhibit excellent OER durability for least 10 h at the 10 mA cm−2. Overall, Co3O4-PNTs with low cost can be serve as a highly reactive and economical catalyst for OER.

The construction of hierarchical hollow Double-Shelled Co3O4 for the enhanced thermal decomposition of Ammonium perchlorate

Ingenious design of catalysts structure is vital for accelerating ammonium perchlorate (AP) thermal decomposition at lower temperature and accompanying with more heat release. In this work, a self-templated approach is adopted to construct hierarchical hollow double-shelled Co3O4 using cobalt glycerate solid spheres as precursors. The structural transformation from the solid species to the hollow double-shelled Co3O4 sphere is implemented by a solution growth combined with a subsequent calcination. The hierarchical hollow double-shelled morphology, large surface area and unique electronic structure endue Co3O4 with enhanced catalytic performance for thermal decomposition of AP. The AP decomposition temperature is decreased to 318 °C and heat release is increased from 491 J g−1 to 1280 J g−1.

A facile strategy to synthesis graphene-wrapped nanoporous copper-cobalt-selenide hollow spheres as an efficient electrode for hybrid supercapacitors

Increasing demands from the electronics industries for fast energy storage devices motivate scientists to spend a tremendous time to design and optimize electrode materials. However, optimizing the full charge cycle requires a highly efficient electrochemical performance that depends on the smart morphological and structural design of the metal compounds and achieving the right chemical composition by taking into consideration the synergistic effect between different elements and the structure effect. Energy storage systems can benefit from the use of Ternary Transition Metal Selenide (TMSe) electrodes; however, the applicability and electrochemical efficiency of these electrodes are hampered by their low active surface area and conductivity. Constructing carbonate materials by introducing binary metal atoms, as well as designing a hollow structure at the nano- and microscales could efficiently overcome these limitations. In this study, we designed a facile self-template approach to preparing porous hollow copper-cobalt selenide microspheres wrapped on conductive networks of reduced graphene oxide (rGO-CCSe). The synthesized electrode is capable of providing considerable capacity retention of 91.5% after 6000 charge cycles through smart structural design and by taking advantage of the bimetallic synergy at the atomic level, with an extremely high specific capacitance of 724 C g−1 at 2 A g−1. Besides, we fabricated an asymmetric cell by using the rGO-CCSe hollow microsphere electrode to achieve very high values for energy densities (57.8 Wh kg−1). The graphene conductive support along with the battery-type CCSe cubics creates a synergistic effect, which accounts for such a remarkable electrochemical output from the rGO-CCSe electrode. In this study, we propose a novel approach to make highly efficient electrodes that can effectively enhance the performance of hybrid supercapacitors used in modern electronic devices.

CoSe2 hollow microspheres with superior oxidase-like activity for ultrasensitive colorimetric biosensing

As one of the transition metal dichalcogenide, CoSe2 has received much attention because of its superior physicochemical properties. In this work, a self-templated approach was proposed for constructing CoSe2 hollow microspheres by utilizing ZIF-67 hollow sphere as a template. In the followed selenylation process, selenium vapor reacts with cobalt ion in ZIF-67 to form CoSe2 microspheres. The obtained CoSe2 microspheres retain the cavity of the ZIF-67 and massive uniformly dispersed CoSe2 nanoparticles are embedded throughout carbon walls. The hollow interior and porous structure of CoSe2 microspheres provide an enhanced surface-volume ratio and short charge/mass transfer distance. The CoSe2 microspheres show a typical oxidase-like property able to promote 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation by dissolved oxygen to produce an intensive color reaction. Reactive oxygen species trials demonstrate that ·OH, 1O2 and O2•− radicals coexist in the TMB-CoSe2 system. Based on its inhibitive role, a rapid and ultrasensitive determination of glutathione was reached, showing four orders of magnitude linear range from 0.005 to 10 μM and a limit of detection of 4.62 nM (S/N = 3). The assay has been successfully used to glutathione determination in practical samples.

PBA@PPy derived N-doped mesoporous carbon nanocages embedded with FeCo alloy nanoparticles for enhanced performance of oxygen reduction reaction

Due to the obstacle of sluggish kinetics on cathode of fuel cells and metal–air batteries, developing low-cost and durable electrocatalysts to replace the platinum-based catalysts still remains a grand challenge. Here, we describe a simple self-template approach to synthesize N-doped mesoporous carbon nanocages (FeCo@NC) embedded with FeCo alloy nanoparticles as oxygen reduction reaction (ORR) electrocatalyst. The resulting heterostructure is derived from corresponding PBA@PPy composites, which are pre-prepared by polymerization of polypyrrole (PPy) layer on Prussian blue analogue (PBA) nanocubes. The FeCo alloy nanoparticles with an average particle size of ∼10 nm are well dispersed and confined within the shell of carbon nanocages. Benefiting from the mesoporous structure and the synergetic interaction of binary metals, the optimized FeCo@NC-3-800 electrocatalyst exhibits comparable ORR performances (0.83 V for half-wave potential (E1/2), 5.323 mA cm−2 for limiting current density (Jk)), superior durability and excellent methanol tolerance to the commercial Pt/C (20 wt%). This work provides an appropriate strategy for general, efficient and practical synthesis of more promising non-precious metal electrocatalyst with high ORR activity.

Engineering Co3+ cations in Co3O4 multishelled microspheres by Mn doping: The roles of Co3+ and oxygen species for sensitive xylene detection

Heteroatom-doping is an effective approach for tuning the properties of transition metal oxides relevant to sensing. Here pristine Co3O4 and a series of Mn-doped Co3O4 multishelled microspheres have been prepared using amorphous-coordination-polymers (CPs). The method is essentially self-templated approach. The as-prepared materials have been used for the development of a gas sensor for detection of volatile organic compounds (VOCs). Results indicate that ∼3 at% Mn-doped Co3O4 multishelled microspheres exhibit enhanced sensing performances, when compared to the pristine Co3O4 multishelled microspheres. Mn cations doping decreases the hole concentration, and aids in the enhancement of the surface catalytic activity which is responsible for the observed performance towards VOCs oxidation.

A self-template approach to synthesize multicore–shell Bi@N-doped carbon nanosheets with interior void space for high-rate and ultrastable potassium storage

Multicore–shell Bi@N–C nanosheets enable high-rate and ultrastable K+ storage.

Formation of resorcinol-formaldehyde hollow nanoshells through a dissolution-regrowth process.

We report here that dissolution and regrowth of resorcinol formaldehyde (RF) colloidal particles can occur spontaneously when they are subjected to etching in solvents such as ethanol and tetrahydrofuran, resulting in the formation of hollow nanostructures with controllable shell thickness. The hollowing process of the RF particles is attributed to their structural inhomogeneity, which results from the successive deposition of oligomers with different chain lengths during their initial growth. As the near-surface layer of RF colloids mainly consists of long-chain oligomers while the inner part consists of short-chain oligomers, selective etching removes the latter and produces the hollow structures. By revealing the important effects of the condensation degree of RF, the etching time and temperature, and the composition of solvents, we demonstrate that the morphology and structure of the resulting RF nanostructures can be conveniently and precisely controlled. This study not only improves our understanding of the structural heterogeneity of colloidal polymer particles, but also provides a practical and universal self-templated approach for the synthesis of hollow nanostructures.