Silica Template Method Research Articles

(Poster Award - 3rd Place) Synthesis of Spherical Mesoporous Carbon (SMPC) Support and Electrochemical Properties of Pt/SMPC Catalyst

Introduction In Japan, extremely high cell performance is required for polymer electrolyte fuel cells (PEFCs) used in fuel cell electric vehicles after 2030 [1]. Therefore, it is of great importance to improve not only ORR activity, but also oxygen diffusivity of Pt and Pt-based cathode catalysts in PEFCs. In this study, a spherical mesoporous carbon (SMPC) with central mesopore’s diameter of 7 nm was synthesized and used for support of the Pt NP catalyst. Electrochemical properties of the Pt/SMPC catalyst were investigated. Experimental The SMPC support was synthesized by silica template method in which SiO2 precursor was in-situ formed [2]. 7 mL of tetrapropyl orthosilicate was added in a mixed solution (6 mL conc. NH3, 150 mL EtOH and 10 mL H2O) and stirred for 15 min. Then, 0.8 g resorcinol and 1.12 mL formaldehyde (37 wt.% aq.) were added and stirred at room temperature for 24 h. The precipitate was filtered and dried at 60°C overnight in air. The powder was heat-treated in a tube furnace at 850°C for 3 h in Ar atmosphere to obtain SiO2/SMPC. The SiO2/SMPC was dispersed in 10% HF aq. and stirred at room temperature for 2 h to remove silica template. The Pt/SMPC catalyst was synthesized by alcohol reduction method [3]. 300 mg SMPC was dispersed in a EtOH/H2O mixed solution (37.5 mL/250 mL), and Pt(NO2)2(NH3)2 (corresponding to 300 mg metallic Pt) dissolved in aqueous HNO3 was added, followed by refluxing at 90°C for 4 h in N2 atmosphere. The catalyst was filtered, washed and dried at 60°C overnight in air. Characterization of SMPC and Pt/SMPC was conducted by N2 gas adsorption, TG-DTA, XRD, TEM and TEM-EDX. The catalyst was loaded on GC-RDE. CV was recorded in Ar-saturated 0.1 M HClO4 at 25oC and at 50 mV/s. The ORR activity was evaluated by LSV performed in O2-saturated 0.1 M HClO4 at 25oC at 10 mV/s in the positive direction while rotating the GC-RDE at 1,600 rpm. Results and Discussion The weight percentage of silica template was 70% in SiO2/SMPC. Figure 1 shows SEM and TEM images of SiO2/SMPC before and after HF treatment. The SEM images clearly show that SiO2/SMPC and SMPC have spherical shape with mean diameter of 200 nm. In TEM images of SiO2/SMPC, center of the sphere is darker than edge and the edge became darker than the center after HF treatment, suggesting that the silica template NPs resided at the center of the sphere. TEM-EDX composition analysis of SiO2/SMPC is demonstrated in Fig. 2. Before HF treatment, Si was detected at the center of the sphere. After HF treatment, only C was detected with high intensities at the edge of the sphere. These results suggest that the SiO2/SMPC has a silica rich core-carbon rich shell structure. The thickness of the carbon rich shell was ca. 60 nm. The surface area of SiO2/SMPC was 510 m2/g and the area increased to 1,590 m2/g after HF treatment. Figure 3 shows pore size distribution of SiO2/SMPC. After HF treatment, SPMC support exhibited clear existence of mesopores with a central diameter of 7 nm.A cross-sectional TEM image of Pt/SMPC catalyst is depicted in Fig. 4. Pt NPs with Scherrer’s diameter of 2.3 nm were well dispersed over the carbon-rich shell, which indicates that mesopores in the carbon shell were well interconnected. The ECSA and the ORR activity of the Pt/SMPC catalyst were 92 m2/g and 450 A/g@0.9 V, respectively, the latter of which was similar to that of a commercially available Pt/C (TKK, TEC10E50E). Single cell tests using Pt/SMPC is now underway, and the results will be presented at the meeting.This study was partly supported by NEDO, Japan. Reference [1] M. Suzuki, https://www.nedo.go.jp/content/100888556.pdf (in Japanese).[2] Z. Deng et al., Nano Lett., 22, 9551 (2022).[3] M. M. Rahman et al., RSC Adv., 11, 20601 (2021). Figure 1

Defected mesoporous carbon nitride with quantum confinement effect for NO purification

Combining mesoporous structure and defect engineering is an effective way to optimize the photocatalytic activity of graphitic carbon nitride. Herein, a unique N-deficient mesoporous carbon nitride (nmpg-C3N4), constructed by silica-template method, possesses efficient and stable photocatalytic purification of NO, far exceeding the bulk carbon nitride (B-C3N4). In nmpg-C3N4, the mesoporous structure not only exposes more active sites, but also the resulting quantum confinement effect widens the band gap of nmpg-C3N4 and enhances its redox ability. While N defects constitute catalytic active sites and induces effective separation of photogenerated carriers. Under the synergistic effect of mesoporous structure and defect engineering, nmpg-C3N4 produces more •O2− and •OH to remove NO in the air. Its photocatalytic activity reaches 60.61% higher than B-C3N4 (35.51%) and exposes better stability. Moreover, a reasonable NO purification path was proposed using in-situ DRIFTS technology. Our research proves that utilizing the quantum confinement effect of mesoporous materials combined with defect engineering can effectively extend the energy band and make the catalyst have more active sites. This study provides new enlightenment for the modification of carbon nitride.

Efficient CO2 adsorption on porous carbon with nitrogen functionalities based on polybenzoxazine: High-pressure adsorption characteristics

Ordered-interconnected porous carbon with nitrogen functionalities is a potential adsorbent for CO2 capture since it could adsorb CO2 gas through both physical and chemical mechanisms. Herein, we reported the preparation of ordered-interconnected porous carbons having nitrogen functionalities based on polybenzoxazine using a silica templating method. The CO2 adsorption measurement was performed at 30 °C and the pressure was varied from 1 to 40 bar. The results showed that the specific surface area (SSA) and pore volume showed a correlation trend indicating the increase with increasing silica templates up to 40 % and the carbon samples contained nitrogen functionalities on the surface (pyrrolic and pyridonic nitrogen, pyridinic nitrogen, and oxidized nitrogen). After CO2 activation, the nitrogen functionalities are still present on the surface of the porous carbon and the sample based on 40 wt% of silica (AC40%Si-800) exhibited the greatest SSA (1,391 m2/g) with extremely large pore volume (3.77 cm3/g). This led to the largest amount of CO2 uptake (25.07 mmol/g at 40 bar) recorded to date. For the first time, the computational study revealed that only pyridinic nitrogen (N-6) is capable of chemically adsorbing CO2 molecules via Lewis acid-base interaction, which synergistically enhanced the adsorption capability.

Significant quantum yield enhancement for near infrared fluorescence dyes by silica templated silver nanorods

Silver's inherent optical properties of low absorption cross section, over a broad wavelength range, makes it an attractive material for use in biosensing. We report herein a unique silica template method to synthesize cetrimonium bromide free silver nanorods (AgNRs). The application of AgNRs in metal enhanced fluorescence (MEF) was explored by immobilizing visible/near-infrared (NIR) fluorescent dyes on AgNR assembled substrates exhibiting broadband optical properties. Theoretical modeling was performed to analyze the nanoscale “chaotic nature” of the AgNR substrates, showing that the plasmon band shifts and broadening were attributed to the resonance coupling between assembled nanorods with different conformations. The quantum yield (QY) of NIR dye Alex Fluor 790 was increased dramatically from 4% to 84%, with total fluorescence enhancement up to two orders of magnitudes. In addition, AgNR substrates can also amplify fluorescence emissions from high quantum yield dyes, nearly 10-fold for Alexa Fluor 647 (QY:33%) and threefold for Alexa Fluor 488 (QY:92%). The AgNR demonstrates the capability of dramatically enhancing NIR dye's QY, holding great potential for building up an ultra-sensitive fluorescence bioassay platform for early diagnosis of diseases.

Aerogel-Derived Fe-N-C Catalysts for Oxygen Electro-Reduction. Linking Their Pore Structure and PEMFC Performance

Iron-based catalysts are intensely investigated for application at the cathode of proton exchange membrane (PEM) and, more recently, of anion exchange membrane fuel cells (AEMFC). Besides optimising their kinetic activity toward the oxygen reduction reaction (ORR), the design and control of their pore structure plays a key role in achieving the highest possible performance in fuel cell. Fe-N-C catalysts derived from the metal-organic framework ZIF-8 are highly active but also mainly microporous, which can lead to mass-transport issues. The silica templating approach typically leads to slightly less active Fe-N-C catalysts, but featuring a combination of micropores and mesopores, which can facilitate mass-transport. Aerogel methods for the synthesis of Fe-N-C catalysts with a hierarchical pore size distribution has been hitherto under-investigated. In contrast to the silica templating method, it is more environmental friendly since no dissolution of a template is needed (no HF). However, highly active Fe-N-C catalysts prepared by aerogel method have not yet been reported in PEM system (even if promising results were recently obtained in rotating disk electrode [1-2]), and it is therefore also unclear if the hierarchical pore size distribution derived from this method is beneficial for improving the mass-transport properties of Fe-N-C cathodes.This presentation will first report the synthesis method and the key parameters investigated, such as the ratio of melamine to resorcinol, the nature and amount of the iron precursor, the addition of an additionnal N-rich ligand, on their ORR activity. The materials were characterized for their texture (N2 sorption, Hg porosimetry), Fe coordination (X-ray absorption and Mössbauer spectroscopy) and surface chemistry (XPS) and morphology. The most promising materials were investigated in PEMFC, for their initial power performance and durability. The results show that, by playing with these synthesis parameters, the aerogel method can yield highly active ORR catalysts (Figure 1), and can give a control on their hierarchical porosity, especially in tuning the mesoporous volume and the average pore width of mesopores. Most catalysts display an atomic dispersion of Fe, explaining their high ORR activity. The presentation will particularly discuss the link between the pore size distribution in this set of materials (micro, meso and macropores), and the mass-transport properties in PEMFC, under pure O2 or air at the cathode. Their durability will also be discussed, from accelerated stress tests performed in rotating disk electrode and/or PEMFC.Acknowledgments:This study was financially supported by the French National Research Agency under the project ANIMA (ANR-19-CE05-0039).

Hydrogen-rich syngas production by the three-dimensional structure of LaNiO3 catalyst from a blend of acetic acid and acetone as a bio-oil model compound

Converting biomass bio-oil to hydrogen is valuable strategy. In this study, a blend of acetic acid and acetone has been utilized as a bio-oil model compound, where perovskite in a three-dimensional structure (3D-LaNiO 3 ) synthesized by a silica template method used as a catalyst. The result shows that the main phase of perovskite at 3D-LaNiO 3 catalyst has lower crystal size, resulting in decrease possibility of agglomeration. The amount of oxygen vacancies and higher ratio of Ni 3+ /Ni 2+ are produced, enhancing the redox of catalyst. The stronger basic site and lager surface indicated the ability of improving coke deposition resistance. These results explained great activity of 3D-LaNiO 3 catalyst in producing hydrogen-rich syngas. The different steam/carbon mole ratios (S/C) have been discussed at 1 to 4, and the gas yield of H 2 (93.5%) shows highest at 600 °C and S/C = 3. Meanwhile, under this condition, the H 2 gas yield was stable and over 90% throughout 15 h of reaction. By analysis of spent 3D-LaNiO 3 catalyst, the result indicated that it has ability to resist the production of graphite coke deposition which is one of reasons for keeping catalyst activity. On the other hand, the stable of perovskite structure help in produce lattice oxygen for oxidizing coke deposited. • Acetic acid and acetone as a bio-oil model compound has been used for H 2 production. • Three-structure of LaNiO 3 has been used as a catalyst and compared with LaNiO 3 . • Three-structure of LaNiO 3 catalyst showed better catalytic performance. • The key factors of the high catalytic activity are oxygen vacancies, crystal size, coke deposition resistance. • Over 90% H 2 yield achieved with three structure -LaNiO 3 catalyst throughout 15 h.

MOF-derived three-dimensional ordered porous carbon nanomaterial for efficient alkaline zinc-air batteries

The design and preparation of non-noble metal catalysts with high catalytic activity and robust stability are important in the research of metal-air batteries and fuel cells. Here, a three-dimensional (3D) hierarchically ordered porous carbon nanomaterial was conveniently synthesized with zeolite-imidazole framework (ZIF-8) carbonization using the silica-template method and carbon nanotube (CNT) growth. The addition of an iron source endows the porous mFeNC-CNT with Fe-based nanoparticles and abundant atomically dispersive Fe-Nx sites from its nitrogen-incorporated graphitic carbon matrix. As a result, the 3D porous structure reduces the charge transport resistance, and the iron and nitrogen codoped carbon exhibits excellent catalytic activity for oxygen reduction reaction (ORR) similar to that of commercial Pt/C. Meanwhile, the interwoven CNTs obtained under urea catalysis further shorten the ion and electron diffusion pathway. Experimental and theoretical analyses revealed that the optimized mFeNC-CNT has a high ORR activity with a half-wave potential of 0.908 V and a large open-circuit voltage (1.556 V) when applied on zinc-air batteries. This work provides a promising strategy for the rational design and facile synthesis of high-performing non-noble metal-based electrocatalysts for energy storage, conversion, and transport applications.

Reinforcement of ultrahigh thermoresistant polybenzimidazole films by hard craters

Ultrahigh thermoresistant polybenzimidazole films with uniform pores and hard craters on the surface were prepared by a silica template method. The pore and crater formation enhanced elongation and Young's modulus.

Influence of Poly(ethylene glycol) Molecular Architecture on Particle Assembly and Ex Vivo Particle-Immune Cell Interactions in Human Blood.

Poly(ethylene glycol) (PEG) is widely used in particle assembly to impart biocompatibility and stealth-like properties in vivo for diverse biomedical applications. Previous studies have examined the effect of PEG molecular weight and PEG coating density on the biological fate of various particles; however, there are few studies that detail the fundamental role of PEG molecular architecture in particle engineering and bio-nano interactions. Herein, we engineered PEG particles using a mesoporous silica (MS) templating method and investigated how the PEG building block architecture impacted the physicochemical properties (e.g., surface chemistry and mechanical characteristics) of the PEG particles and subsequently modulated particle-immune cell interactions in human blood. Varying the PEG architecture from 3-arm to 4-arm, 6-arm, and 8-arm generated PEG particles with a denser, stiffer structure, with increasing elastic modulus from 1.5 to 14.9 kPa, inducing an increasing level of immune cell association (from 15% for 3-arm to 45% for 8-arm) with monocytes. In contrast, the precursor PEG particles with the template intact (MS@PEG) were stiffer and generally displayed higher levels of immune cell association but showed the opposite trend-immune cell association decreased with increasing PEG arm numbers. Proteomics analysis demonstrated that the biomolecular corona that formed on the PEG particles minimally influenced particle-immune cell interactions, whereas the MS@PEG particle-cell interactions correlated with the composition of the corona that was abundant in histidine-rich glycoproteins. Our work highlights the role of PEG architecture in the design of stealth PEG-based particles, thus providing a link between the synthetic nature of particles and their biological behavior in blood.

Targeted poly(ethylene glycol) nanoparticles for photodynamic therapy

A challenge for nanomedicine is to improve their targeting ability and avoid nonspecific interactions with the surrounding environments. Herein, we report the fabrication of photosensitizer-loaded poly(ethylene glycol) nanoparticles (PEG NPs) with high targeting ability to inhibit cancer cell growth. PEG NPs are prepared via a mesoporous silica (MS) templating method and functionalized with cyclic Arg-Gly-Asp (RGD) peptides for specific targeting to U87 MG cells expressed with αvβ3 integrins. Chlorin e6 (Ce6) as a photosensitizer is conjugated onto PEG and encapsulated into PEG NPs for photodynamic therapy (PDT). The obtained PEG-Ce6-RGD NPs can efficiently target to U87 MG cells and improve the PDT efficacy. Our approach provides an avenue to engineer targeted polymer carriers for PDT.

X‐Ray‐Induced Persistent Luminescence Promotes Ultrasensitive Imaging and Effective Inhibition of Orthotopic Hepatic Tumors

AbstractPersistent luminescence imaging is accompanied by continuous illumination after the removal of excitation light, which can successfully prevent the generation of autofluorescence. In this study, a mesoporous silica template method is used to prepare uniform and monodisperse porous nanophosphors that can generate X‐ray‐excited persistent luminescence (XEPL). By loading photosensitizers, XEPL effectively excites the photosensitizers to produce reactive oxygen species for killing cancer cells. Imaging of orthotopic hepatic tumors in vivo shows that nanophosphors accumulate in the liver tumors through a passive targeting mechanism, as confirmed by the co‐imaging of bioluminescence and X‐ray‐excited luminescence. Under image‐guidance, X‐ray‐induced photodynamic therapy effectively inhibits the growth of orthotopic hepatic tumors with negligible side effects. Overall, X‐ray‐induced persistent luminescence promotes ultrasensitive imaging and effective inhibition of orthotopic hepatic tumors.

A Nano-Rattle SnO2@carbon Composite Anode Material for High-Energy Li-ion Batteries by Melt Diffusion Impregnation.

The huge volume expansion in Sn-based alloy anode materials (up to 360%) leads to a dramatic mechanical stress and breaking of particles, resulting in the loss of conductivity and thereby capacity fading. To overcome this issue, SnO2@C nano-rattle composites based on <10 nm SnO2 nanoparticles in and on porous amorphous carbon spheres were synthesized using a silica template and tin melting diffusion method. Such SnO2@C nano-rattle composite electrodes provided two electrochemical processes: a partially reversible process of the SnO2 reduction to metallic Sn at 0.8 V vs. Li+/Li and a reversible process of alloying/dealloying of LixSny at 0.5 V vs. Li+/Li. Good performance could be achieved by controlling the particle sizes of SnO2 and carbon, the pore size of carbon, and the distribution of SnO2 nanoparticles on the carbon shells. Finally, the areal capacity of SnO2@C prepared by the melt diffusion process was increased due to the higher loading of SnO2 nanoparticles into the hollow carbon spheres, as compared with Sn impregnation by a reducing agent.

Dual-Stimuli-Responsive Polypeptide Nanoparticles for Photothermal and Photodynamic Therapy.

We report the assembly of dual-responsive polypeptide nanoparticles loaded with indocyanine green (ICG) using a mesoporous silica (MS) templating method for photothermal and photodynamic therapy. Polypeptide nanoparticles composed of thiol-modified polylysine (PLL) are cross-linked with disulfide bonds and modified with poly(ethylene glycol) (PEG) and pH-sheddable dimethylmaleic anhydride (DMMA), which exhibit reduction- and pH-responsiveness. Cross-linking with disulfide bonds does not influence the free amine groups on PLL chains for further cargo conjugation and surface modification. The stripped DMMA at acidic pH reverses the zeta potential of PLL nanoparticles from negative to positive charge and subsequently results in high cell association. The thermo-responsiveness and singlet oxygen generation of the loaded ICG in DMMA-modified PLL nanoparticles are comparable to those of free ICG under laser irradiation, which induces higher cytotoxicity to cancer cells compared to succinic anhydride (SA)-modified PLL nanoparticles that are not pH-responsive. The reported dual-responsive PLL nanoparticles provide a promising platform for improved photothermal and photodynamic therapy.

Vertically grown and intertwined Co(OH)2 nanosheet@Ni-mesh network for transparent flexible supercapacitor

Pseudo-capacitive materials have attracted great attention as electrode materials for supercapacitor owing to their high specific capacitance, high energy densities, and high rate capability. However, performances of pseudo-capacitive materials as transparent flexible supercapacitors are limited due to their non-transparent characteristics and brittleness in nature. Herein, we report a scalable, low-cost, and opto-electrochemical tunable, high-performance core-shell Co(OH)2@Ni-mesh network transparent flexible supercapacitor electrode using a simple cracked silica template method in combination with metal deposition and electrochemical deposition technique. A seamless highly-conducting (~24 Ω/sq), transparent Ni-mesh network (~87%) was first fabricated using cracked silica template and etching method. In particular, a cracked silica template enables fabrication of a junction-less, high-aspect-ratio Ni-mesh network which substantially improves conductivity without considerably sacrificing transparency. The Ni-mesh network as flexible transparent current collector high pseudo-capacitive material, Co(OH)2 nanosheets were then electrodeposited over Ni-mesh network electrode. The growth of vertically aligned and intertwined Co(OH)2 nanosheets over Ni-mesh network electrodes results in high electrochemical performance of the electrode at high transparency. The core-shell Co(OH)2@Ni-mesh network electrode with the transparency of ~75% demonstrated an areal capacitance of 22.9 mF/cm2 at 5 mV/s scan rate, exhibiting excellent mechanical flexibility along with high rate capability. Moreover, the fabricated symmetric transparent flexible supercapacitor device exhibited a high areal cell capacitance of 5.32 mF/cm2 at 5 mV/s scan rate at a transparency of ~54%, showing high rate capability, long cycling stability, excellent mechanical bendability along with high energy density of 0.42 μWh/cm2 and power density of 8.33 μW/cm2.

A direct H2O2 production based on hollow porous carbon sphere-sulfur nanocrystal composites by confinement effect as oxygen reduction electrocatalysts

Carbon-sulfur composites have drawn increasing interest in various fields including electrocatalysis because of their unique structures. However, carbon-sulfur composite with tiny sulfur nanocrystals has still received little attention. Herein, hollow porous carbon sphere-sulfur composite (HPCS-S) which possesses excellent electrochemical performance towards H2O2 has been prepared for the first time via a simple silica template method. The 2–5 nm sulfur nanocrystals being restricted in the channel of the hollow porous carbon spheres are under a strong compressive stress, which was further confirmed by HRTEM and GPA. The HPCS-S nanocrystals show better conductivity than amorphous sulfur clusters because of the reduction of the steric hindrance which efficiently promotes the electron transportation. Consequently, the higher activity and selectivity towards the 2e- oxygen reduction reaction (ORR) to H2O2 in alkaline solution was obtained. The H2O2 selectivity rises from 20% to over 70% after the sulfur addition and the H2O2 production rate achieves 183.99 mmol·gcatalyst-1 with the Faradaic efficiency of 70%. Furthermore, performance enhancement mechanism was also investigated using the density functional theory (DFT) calculations. After the introducing of sulfur nanocrystals, the appearance of S-S bond greatly decreases the overpotential compared with S-doping, which results in significant enhancement of the electrocatalytic property. Consequently, the HPCS-S can be an efficient H2O2 production electrocatalyst in alkaline solution.

Self-healing epoxy nanocomposite coatings based on dual-encapsulation of nano-carbon hollow spheres with film-forming resin and curing agent

The ability of an active protective organic coating to restore its protection functionality in case of a coating defect is of pivotal importance to ensure durable performance under demanding corrosive conditions. In this paper, a self-healing epoxy system is fabricated by separate encapsulation of epoxy and polyamine in carbon hollow spheres (CHSs) and the autonomous healing performance of the system applied on mild steel is investigated. CHSs were synthesized via a silica templating method using carbonization of polysaccharide shells formed on the surface of silica templates. Consequently, epoxy and polyamine were loaded in separate capsules by dispersion of CHSs into the dilute solutions of epoxy/acetone and polyamine/acetone respectively, under vacuum conditions. The synthesized CHSs were characterized before and after the silica removal using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The CHSs loaded with the film forming agents were assessed using thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the protective and self-healing properties of the coatings fabricated were studied using electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET) and salt spray testing. The results showed that scribe defects in epoxy coatings with 10 wt % epoxy and polyamine capsules were healed effectively upon efficient release and subsequent recombination of the epoxy and polyamine agents reforming a protective layer at the damaged region.

Copper-Doped Cobalt Spinel Electrocatalysts Supported on Activated Carbon for Hydrogen Evolution Reaction.

The development of electrocatalysts based on the doping of copper over cobalt spinel supported on a microporous activated carbon has been studied. Both copper–cobalt and cobalt spinel nanoparticles were synthesized using a silica-template method. Hybrid materials consisting of an activated carbon (AC), cobalt oxide (Co3O4), and copper-doped cobalt oxide (CuCo2O4) nanoparticles, were obtained by dry mixing technique and evaluated as electrocatalysts in alkaline media for hydrogen evolution reaction. Physical mixtures containing 5, 10, and 20 wt.% of Co3O4 or CuCo2O4 with a highly microporous activated carbon were prepared and characterized by XRD, TEM, XPS, physical adsorption of gases, and electrochemical techniques. The electrochemical tests revealed that the electrodes containing copper as the dopant cation result in a lower overpotential and higher current density for the hydrogen evolution reaction.

Preparation of nitrogen-doped hollow carbon spheres for sensitive catechol electrochemical sensing

In this work, nitrogen-doped hollow carbon spheres (NCs) were prepared by a silica template method using dopamine as a carbon precursor. The as-prepared NCs were used to fabricate a catechol (CC) electrochemical sensor. Nitrogen doping significantly enhances the conductivity of the electrode. Therefore, NCs were successfully used to modify screen-printed electrodes, which exhibited excellent sensing performance. Under the optimized conditions, the prepared electrochemical sensor could linearly detect CC between 0.5 and 300 μM with a low detection limit of 0.14 μM.

Colloidal Silica Templated Mesoporous Carbons from a Maltose Solution for Use in Supercapacitor Electrodes.

A series of disordered mesoporous carbons (DMC) are synthesized via the colloidal silica template method by varying the mass ratio of silica to maltose from 0.4 to 1.4. A gradual improvement in the surface area and porosity of the DMC is apparent with an increase in the ratio of silica to maltose. The capacitance of the DMCs tends to increase linearly with their surface area. In particular, the DMC synthesized at a mass ratio of 1.4 exhibits the largest surface area of 1,152 m2/g and the highest capacitance of 175.4 F/g, comparable to the capacitance of other porous carbons with large surface areas (>2,000 m2/g). This feature may be attributed to its unique structural properties, such as the high pore interconnectivity allowing for easy access of the electrolyte ions. We believe that a higher capacitive performance can be achieved through further optimization studies (e.g., searching for better carbon precursors and adjusting the mass ratio of silica to carbon precursor).

Fabrication and characterization of graphene-based carbon hollow spheres for encapsulation of organic corrosion inhibitors

In this work, we synthesized carbon hollow spheres (CHSs) using the silica templating method, encapsulated 2-mercaptobenzimidazole (MBI) inhibitor in the CHSs and evaluated their corrosion inhibition performance upon exposure of mild steel to a saline solution containing the released inhibitor. The effects of silica template surface modification on the CHS structure was evaluated, while the structure and morphology of the synthesized CHS was analyzed using field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), Raman spectroscopy and X-ray diffraction (XRD) spectroscopy. Furthermore, thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy mapping (EDS-mapping) and UV–vis were employed to evaluate the MBI release from carbon capsules at different pH values. Corrosion protection performance of the doped CHS was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results showed tunability of the shell structure between an amorphous carbon and graphene structure using surface modification of the silica templates. Moreover, the MBI release from the CHSs showed to be pH-dependent allowing smart protection of mild steel when exposed to corrosive conditions.