Resorcinol-formaldehyde Resin Research Articles

Construction of N-Doped Hollow Carbon Nanospheres Through a Novel Self-Template Strategy as High-Performance Electrode Materials for Supercapacitors

N-doped hollow carbon nanospheres (NHCSs) with mesopores-rich hierarchical structure have been synthesized by a self-template strategy using resorcinol-formaldehyde resin as precursors. The crucial point of this strategy is the selective dissolution of acetones for oligomers and subsequent rearrangement dependent on the structure-directing agent (CTAB). The large specific surface area (1325.0 m2 g−1), abundant and accessible mesopores (6.6 nm), unexpected nitrogen doping concentration (3.5 wt.%), and favorable graphitization (0.88), enable the as-prepared NHCSs to be a candidate for energy storage materials. When utilized as supercapacitor electrode, the NHCSs exhibit high specific capacitance of 293.1 F g−1 at 0.5 A g−1, impressive rate performance of 225.0 F g−1 at 20 A g−1, and good cycling performance (over 88.24% the peak capacity was retained after 5000 cycles at 5 A g−1). The self-template strategy displays potential prospects as a versatile route to reconstruct porous structures of carbon materials from phenolic resin polymers, thereby broadening the applications in drug delivery, adsorption, and energy storage systems.

Polythiophene-Doped Resorcinol-Formaldehyde Resin Photocatalysts for Solar-to-Hydrogen Peroxide Energy Conversion.

The generation of hydrogen peroxide (H2O2) from water and dioxygen by sunlight-driven heterogeneous photocatalysis is a promising method for the artificial photosynthesis of a liquid solar fuel. We previously found that resorcinol-formaldehyde (RF) resin powders prepared by high-temperature hydrothermal synthesis act as highly active semiconductor photocatalysts for H2O2 generation. Herein, we report that RF resin powders doped with poly(3-hexylthiophene-2,5-diyl) (RF/P3HT) exhibit enhanced photocatalytic activities. The highly dispersed P3HT within the resin particles created charge transfer complexes with the conduction band of the resin via electron donation, facilitating efficient transfer of the photogenerated conduction band electrons through P3HT. This enhanced charge separation promoted efficient water oxidation and O2 reduction. The solar-to-chemical conversion efficiency for H2O2 generation on the RF/P3HT resin in water under simulated sunlight irradiation with atmospheric pressure of O2 was ∼1.0%, which is the highest efficiency reported for powder catalysts in artificial photosynthesis.

Synthesis, characterization and photocatalytic properties of robust resorcinol-formaldehyde polymer fine particles

For design and development of effective visible-light responsible artificial photocatalytic system, resorcinol-formaldehyde (RF) resin polymer photocatalysts have been extensively studied. The RF resin polymer fine particles with different compositions were systematically prepared by hydrothermal synthesis. The RF polymers were characterized by UV–vis, XRD, SEM, FT-IR, electrochemical impedance spectroscopy, photoelectrochemical response, and DFT calculation. Attention was much paid to effects of R/F molar compositions and the preparation temperatures of the RF polymers on their photocatalytic activities for H2O2 production from O2 and H2O. Furthermore, the charge transfer complexes formed by the interaction of benzenoid OH with quinone CO were found to play a vital role in the photocatalytic reactions under visible-light irradiation.

Investigation of in-situ polymerization synthesized carbon-coated zinc oxide as anode material for Zn/Ni secondary battery

Using the resorcinol-formaldehyde (RF) resin as carbon source, core-shell structured carbon-coated zinc oxide (ZnO@RFC) was synthesized by cetyltrimethylammonium bromide (CTAB) assisted in-situ polymerization followed with carbonization process. The results showed that the ZnO particles were uniformly coated by an amorphous carbon layer. The excellent structural stability and high electrochemical performance depend it to be designed into carbon shell with a tunable thickness up to 14.4 nm, resulting in the ZnO@RFC anode delivers initial discharge specific capacity of 543 mAh g−1 and optimized 125 cycle life with capacity retention of 97.5% for Zn/Ni secondary batteries. And the effects of the thickness of carbon shell on electrochemical performance, corrosion and hydrogen evolution reaction are fully investigated. The results indicate that the carbon shell not only improves the electrical conductivity between ZnO particles but also increases the stability of ZnO in electrolyte.

Carbon Aerogel Based Waterborne Ultra-Black Coatings with High Light Absorption

In this paper, we wish to report the preparation of ultra-black films via spraying coatings composed of waterborne binders and low-cost carbon aerogels on pre-treated tinplate. The CAs were prepared by annealing resorcinol-formaldehyde resin (RF resin) and the following CO2 activation, of which the reflectance was less than 0.4% in a wide wavelength range. The reflectance of different coatings, which using CAs as functional pigments, ranged from 1.8% to 4.3% in the visible light region (400−760 nm), while it ranged from 1.9% to 4.2% in the near-infrared region (760–1100 nm). Further studies revealed the relationship between the pigment-to-binder ratio and reflectance and found the best ratio to be 0.96, and the minimum reflection was less than 1.8%. Outstanding adhesion to the tinplate substrate was also achieved using a two-component polyurethane binder after the thermal cycling test carried out from −100 °C to 100 °C. The fabrication process of ultra-black coatings is particularly convenient to remove the constraints of high costs and complex processes, making it instructive guidance for industrial production.

Facile fabrication of nanocarriers with yolk-shell mesoporous silica nanoparticles for effective drug delivery

Drug delivery systems (DDSs) can greatly reduce the negative impact of chemotherapy in the treatment of tumors by alleviating issues such as low solubility, short half-life, and strong side effects of chemotherapeutic drugs. Therefore, engineering DDSs is of great significance. Herein, we report an innovative magnetic delivery system with a yolk-shell structure and targeting function, comprising a magnetic core and a mesoporous silica shell. The yolk-shell-structure was fabricated by the swelling-shrinkage process of resorcinol-formaldehyde resin upon soaking in or removal of hexane, while a silica shell was formed. The hydrophobic resin layer, hollow cavity, and channels of the shell improved the drug loading and afforded sustained drug release. The desired drug carriers (denoted as Fe3O4@YSSiO2-FA) were labeled with folate to promote biocompatibility and targeting functions. The prepared Fe3O4@YSSiO2-FA with particle sizes ranging from 100 to 200 nm had a loading capacity of 220 μg mg−1 for camptothecin (CPT) and afforded sustained release over 72 h in vitro. Fe3O4@YSSiO2-FA presented a lower protein adsorption capacity, a hemolysis rate of less than 1.2%, and weak cytotoxicity for A549 cells, with a cell viability of more than 74%, indicating that the proposed nanocarriers possess excellent biocompatibility. CPT-loaded Fe3O4@YSSiO2-FA showed higher cytotoxicity for KB cells (FA-receptor-positive) due to the higher cellular uptake compared to A549 cells (FA-receptor-negative), likely suggesting a preeminent tumor-specific targeting ability. The superior loading capacity, targeting ability, and biocompatibility demonstrate that Fe3O4@YSSiO2-FA possesses great potential as a carrier for DDSs. As expected, the developed strategy provides a facile alternative for fabricating efficient DDSs for antitumor applications.

Hydrothermal oxidation of pre-dissolved resorcinol-formaldehyde resins as a new approach to safe processing of spent cesium-selective organic ion-exchangers

Here we report a new approach to predisposal processing of spent resorcinol-formaldehyde resins (RFR) selective to cesium radionuclides via dissolution and hydrothermal oxidation (HTO) with the mineralization efficiency above 85%. Using a combination of potentiometric and colloid titration, we have shown that dissolution of RFR by consecutive treatment with nitric acid and sodium hydroxide solutions at optimal concentrations of 3–5 mol/L and 1 mol/L, respectively, yields colloid solutions of partially depolymerized and oxidized RFR. The efficiency of HTO of resorcinol and RFR solutions with hydrogen peroxide was investigated in a flow-type stainless steel reactor in the temperature range 165–250 °С and at linear flow rates of 1–3 cm/min. It was demonstrated that HTO allowed efficient resorcinol mineralization using hydrogen peroxide at H2O2: resorcinol molar ratios above 10 at 195 °С and a linear flow rate of 2 cm/min. Due to the colloidal nature of organics in RFR solution, its efficient decomposition occurred at higher temperature or molar excess of the oxidizer as compared to resorcinol, but in both cases HTO was the most efficient in acidic media yielding acetic acid as the main oxidation resistant product.

Synthesis of dendritic porous silica nanospheres coated by polymer layer with well-dispersed ultrasmall Pt nanoparticles

It is highly desired but challenging to achieve uniform and high-density loading of ultrasmall active species on porous carriers for excellent performance in various applications. Herein, we successfully used aminopropyl-modified dendritic porous silica nanospheres (DPSNs-NH2) as a carrier to prepare the polymer-coated DPSNs-NH2 with many ultrasmall Pt NPs by one-step ammonia-catalyzed resorcinol-formaldehyde (RF) resin polymerization and formaldehyde-caused H2PtCl6 reduction (named as DPSNs-NH2@RF@Pt nanocomposite). High-density Pt NPs with a mean size of ca. 0.9 nm are uniformly dispersed on and in the RF resin layer, which is coated on the surface of center-radial large pores of DPSNs. In addition, the thickness of RF resin layer can be simply adjusted by tuning the amount of precursors. DPSNs-NH2@RF@Pt nanocomposite exhibits excellent structure stability upon long time ultrasonic treatment, which should be mainly attributed to the partial embedding of Pt NPs on and in the RF resin layer. These results should provide some insight for the design and construction of the supported nanocatalysts.

Mild resorcinol formaldehyde resin polymer based immunochromatography assay for high-sensitive detection of clenbuterol

Abstract Exploring a nanomaterial simultaneously possessing simple synthesis process and brighter colors as a novel label is urgently needed in the immunochromatography assay (ICA). Herein, in order to achieve high-sensitive detection of small molecule pollutants, an immunosensor is developed, where the mild resorcinol formaldehyde resin polymer (mRF, 380 nm) synthesized under mild conditions, was applied as a signal label. The mRF possesses good biocompatibility, various chemical groups, and is easy to bind biological molecules. The antibody was connected to the mRF through electrostatic adsorption to prepare immune probes that was further applied in ICA. In this work, clenbuterol (CL) was chosen as the analysis model to prove the performance of the mRF-based immune probe. Under best conditions, the detection sensitivity is 1 ng mL−1, that is 4 times lower than that of as much sensitive as the traditional colloidal gold strip. In addition, this method was successfully applied to detect CL in food samples, with recovery rates between 96.7 % and 117.2 %. These results show that the mRF-based ICA is a reliable and sensitive detection tool for the CL residue. This work offers a new possibility for the application of RF and a new reference method for the analysis and detection of other small molecule pollutants.

Preparation of manganese oxide-porous carbon nanocomposites by self-activation and their enhanced performance for methylene blue degradation

Manganese oxides and their composites are promising catalysts for the Fenton-like reaction, which generates hydroxyl radical to eliminate the ever-growing organic pollutants in water. Here, a new solution synthesis approach combined with the self-activation carbonization process has been developed to prepare the MnOx-porous carbon nanocomposites (MnOx-C(SiO2)). First, Mn ions are easily incorporated into resorcinol-formaldehyde (RF) resin with the help of polyacrylic acid (PAA) and then transformed into MnOx particles during carbonization. When the Mn-RF sphere is coated in a silica shell in advance, the pyrolysis process can endow the product with a high BET surface area of 962.8 m2 g−1, much larger than that of the counterpart prepared without SiO2 coating (MnOx-C). In the meantime, the SiO2 shell also prevents the in situ formed MnOx particles from getting larger, making them well dispersed in the porous carbon. The size of MnOx particles in MnOx-C(SiO2) is only 5 nm, which shows superior catalytic performance toward methylene blue (MB) degradation via the Fenton process. The MB degradation rate is close to 100% and remains 98.9% after five cycles.

Construction of Oxygen-Rich Carbon Foams for Rapid Carbon Dioxide Capture.

As carbon dioxide (CO2) adsorbents, porous materials with high specific surface areas and abundant CO2-philic groups always exhibit high CO2 capacities. Based on this consensus, a category of oxygen-rich macroporous carbon foams was fabricated from macroporous resorcinol-formaldehyde resins (PRFs), which were obtained via an oil-in-water concentrated emulsion. By the active effect of potassium hydroxide (KOH) at high temperatures, the resultant carbon foams (ACRFs) possessed abundant micropores with rich oxygen content simultaneously. At the same time, most of the ACRFs could retain the marcoporous structure of their precursor. It is found that porosity of ACRFs was mainly determined by carbonization temperature, and the highest specific surface areas and total pore volume of ACRFs could reach 2046 m2/g and 0.900 cm3/g, respectively. At 273 K, ACRFs showed highest CO2 capacity as 271 mg/g at 1 bar and 91.5 mg at 15 kPa. Furthermore, it is shown that the ultra-micropore volume was mainly responsible for the CO2 capacities of ACRFs at 1 bar, and CO2 capacities at 15 kPa were mainly affected by the oxygen content. It is also found that the presence of macropores would accelerate ACRFs adsorbing CO2. This study provides ideas for designing a porous CO2 adsorbent.

Synthesis of multiple Ag nanoparticles loaded hollow mesoporous carbon spheres for highly efficient and recyclable catalysis

Multiple Ag nanoparticles loaded hollow mesoporous carbon spheres ([email protected]) are successfully synthesized through a “soft-to-hard templating” approach. In this method, polyacrylic acid (PAA) colloids are used as stabilizers for Ag nanoparticles and serve as soft templates for a sol-gel process with tetraethyl orthosilicate and polymerization process of resorcinol-formaldehyde resin (RF resin) in one pot. [email protected] are obtained after carbonization of the RF resin layer and selectively etching the SiO2 component. [email protected] exhibit a spherical morphology with a mean size of approximately 140 nm and a high surface area of 239.67 m2 g−1, and the average size of encapsulated silver nanoparticles are about 10 nm without aggregation. The prepared [email protected] show excellent catalytic activity and stability for reduction of 4-nitrophenol, Congo red, and Rhodamine B. Therefore, this “soft-to-hard templating” approach represents a promising strategy for the preparation of high-performance carbon nanoparticle-supported catalysts.

PEO-b-PS Block Copolymer Templated Mesoporous Carbons: A Comparative Study of Nitrogen and Sulfur Doping in the Oxygen Reduction Reaction to Hydrogen Peroxide.

Carbon materials slightly doped with heteroatoms such as nitrogen (N-RFC) or sulfur (S-RFC) are investigated as active catalysts for the electrochemical bielectronic oxygen reduction reaction (ORR) to H2 O2 . Mesoporous carbons with wide, accessible pores were prepared by pyrolysis of a resorcinol-formaldehyde resin using a PEO-b-PS block copolymer as a sacrificial templating agent and the nitrogen and sulfur doping were accomplished in a second thermal treatment employing 1,10-phenanthroline and dibenzothiophene as nitrogen and sulfur precursors, respectively. The synthetic strategy allowed to obtain carbon materials with very high surface area and mesopore volume without any further physicochemical post treatment. Voltammetric rotating ring-disk measurements in combination with potentiostatic and galvanostatic bulk electrolysis measurements in 0.5 m H2 SO4 demonstrated a pronounced effect of heteroatom doping and mesopores volume on the catalytic activity and selectivity for H2 O2 . N-RFC electrode was employed as electrode material in a 45 h electrolysis showing a constant H2 O2 production of 298 mmol g-1 h-1 (millimoles of H2 O2 divided by mass of catalyst and electrolysis time), with a faradic efficiency (FE) up to 61 % and without any clear evidence of degradation. The undoped carbon RFC showed a lower production rate (218 mmol g-1 h-1 ) but a higher FE of 76 %, while the performances drastically dropped when S-RFC (production rate 11 mmol g-1 h-1 and FE=39 %) was used.

N-doped mesoporous carbon nanosheets for supercapacitors with high performance

Due to the characteristics of thin thickness, rich active sites and short diffusion distance, the carbon nanosheets have been widely used as electrodes for energy storage in supercapacitors. Herein, N-doped mesoporous carbon nanosheets (N-MCS) were prepared by using cheap mica powder as template and resorcinol-formaldehyde (RF) resin as carbon precursor. The ethyl orthosilicate (TEOS) was introduces as porogen to create rich mesopores and to increase surface area. The ethylenediamine can be used not only as catalyst for TEOS hydrolysis and RF resin polymerization, but also as nitrogen dopant. The N-MCS faithfully replicated the template morphology, exhibiting sheet-like morphology, porous and N-doping characteristics, which can effectively improve the electrochemical performance.

Synthesis of rattle-structured CuCo2O4 nanospheres with tunable sizes based on heterogeneous contraction and their ultrahigh performance toward ammonia borane hydrolysis

Micro/nano-materials with rattle-type structures are attractive because of their unique physicochemical properties and extensive applications. In this study, well-defined rattle-type CuCo2O4 nanospheres were fabricated by heterogeneous contraction caused by non-equilibrium heat treatment with the assistance of an RF (resorcinol formaldehyde) resin colloidal sphere hard template. The sizes of CuCo2O4 nanospheres could be tuned by varying the amount of NH3·H2O used during template synthesis. The possible formation mechanism of rattle-type CuCo2O4 nanospheres was also proposed. When used in ammonia borane hydrolysis, rattle-type CuCo2O4 nanospheres exhibited ultrahigh activity with a turnover frequency of 104.0 min−1, which is one of the highest activities of non-noble-metal based catalysts, and is even higher than many noble-metal-based catalysts. This research provides valuable insights into the development of robust catalysts for ammonia borane hydrolysis. In addition, the synthetic method presented in this work can be easily extended to prepare other oxide composites with rattle structures.

Solar-to-hydrogen peroxide energy conversion on resorcinol\u2013formaldehyde resin photocatalysts prepared by acid-catalysed polycondensation

The photocatalytic generation of hydrogen peroxide from water and dioxygen (H2O + 1/2O2 → H2O2, ΔG° = +117 kJ mol–1) under sunlight is a promising strategy for the artificial photosynthesis of a liquid fuel. We had previously found that resorcinol–formaldehyde (RF) resin powders prepared by the base-catalysed high-temperature hydrothermal method act as semiconductor photocatalysts for H2O2 generation. Herein, we report that RF resins prepared by the acid-catalysed high-temperature hydrothermal method (~523 K) using common acids at pH < 4 exhibit enhanced photocatalytic activity. The base- and acid-catalysed methods both produce methylene- and methine-bridged resins consisting of π-conjugated and π-stacked benzenoid–quinoid donor–acceptor resorcinol units. The acidic conditions result in the resins with a lower bandgap (1.7 eV) and higher conductivity because the lower-degree of crosslinking creates a strongly π-stacked architecture. The irradiation of the RF-acid resins with simulated sunlight in water with atmospheric-pressure O2 generates H2O2 at a solar-to-chemical conversion efficiency of 0.7%, which is the highest efficiency ever reported for powder catalysts used in artificial photosynthesis.

Preparation of Carbon Monolith Derived from Resorcinol-Formaldehyde Resin and Its Application for Antibiotic Adsorption

The presence of antibiotics in wastewater discharged to the waterbody has negative effects. The antibiotics can induce bacteria to be persistent. Hence, efforts to limit the concentration of antibiotics in wastewater are required. In this work, the removal of antibiotics was performed by adsorption using nanoporous carbon in the form of a monolith. The carbon monolith was prepared by pyrolysis of templated resorcinol formaldehyde polymer at 600°C and 800°C. The material was characterized systematically by scanning electron microscopy and an N2-sorption analyzer. As a comparison, commercial carbon of coconut shell-derived was also employed in the study. The characterization showed that porous carbon monolith has a high specific surface area up to 594 m2/g. In the adsorption test, the results indicated that carbon monolith was better at adsorbing antibiotics compared to the commercial one.

Preparation of an N-doped mesoporous carbon sphere and sheet composite as a high-performance supercapacitor

Carbon-based materials with multidimensional structures generally exhibit improved properties compared with single-morphology carbon materials for various applications including catalysis, adsorption, and energy storage. Here, an N-doped mesoporous carbon sphere and sheet composite is prepared by a co-assembly strategy using an ionic liquid ([C18Mim]Br) as the structure-directing agent, ethylenediamine as the catalyst, tetraethyl orthosilicate as the pore-forming agent, and resorcinol formaldehyde resin as the carbon precursor. [C18Mim]Br and ethylenediamine not only induce formation of the unique structure but also lead to in situ nitrogen doping on the N-doped mesoporous carbon skeleton. The obtained N-doped mesoporous carbon shows a unique composite structure of thin sheets embedded with carbon spheres, having high a specific surface area and uniform mesopore distribution. When used as an electrode material, the N-doped mesoporous carbon shows a good specific capacity of 273 F g−1 at a current density of 0.5 A g−1 and a good rate capability (82.1% of the capacitance is retained at a high current density of 10 A g−1). Moreover, the N-doped mesoporous carbon exhibited ideal stability behavior (91.6% capacitive retention after 10,000 cycles), indicating a promising role as an electrode material for excellent performance supercapacitors.

ZIF-derived ZnO/Sb composite scaffolded on carbon framework for Ni-Zn batteries

Ni-Zn, Zn-MnO2, and Zn-air batteries have the advantages of inflammability, material abundance, and high specific energy. However, their applications are limited by the poor rechargeability of zinc anodes, which are related to shape changes, dendrite growth, corrosion, passivation, dissolution, etc. In this study, we developed a zeolitic-imidazolate framework (ZIF)-based route to construct a novel ZnO/Sb composite anode. The resultant zinc anode is scaffolded on carbon cloth (CC) and then encapsulated by carbonized resorcinol-formaldehyde resins. Such a carbon-framed ZnO/Sb anode shows the excellent rate and cycling properties because Sb suppresses the corrosion and improves interparticle conductivity, and the ZIF-derived carbon frame accommodates the shape changes, blocks the zinc dissolution, and accelerates the charge transfer. This work demonstrates the effectiveness of anti-corrosion and carbon-framed structure design on pouch and cable-like Ni-Zn batteries.

Artificial Bifunctional Photozyme of Glucose Oxidase-Peroxidase for Solar-Powered Glucose-Peroxide Detection in a Biofluid with Resorcinol-Formaldehyde Polymers.

Photozymes or artificial photosynthesis based on alternative natural enzymes is vital for the sustainable development of next-generation healthcare, energy, and materials science. Herein, we report resorcinol-formaldehyde (RF) resins as a solar-driven metal-free bifunctional glucose oxidase-peroxidase stand-alone photozyme for the colorimetric dual detection of hydrogen peroxide and glucose. The π-bond conjugated benzenoid-ortho/para quinoid RF polymers are efficient for glucose oxidation and hydrogen peroxide reduction with concurrent 3,3',5,5'-tetramethylbenzidine oxidation under natural sunlight. The photoinduced colorimetric process could detect H2O2 up to 3.5 μM at 652 nm with the linear range of 0.1-2 mM. A limit of detection of 9.2 μM was exhibited by the system while measuring glucose with a linearity from 0.2 to 8.5 mM. The formation of hydroxyl radicals (•OH) from glucose oxidation reactions was evidenced by spin trapping electron paramagnetic resonance studies conducted herein. The results indicated that RF resins possessed strong intrinsic glucose oxidase and peroxidase (POx)-like activity under natural sunlight with promising storage and operation. This simple photozyme will definitely have potential uses in biomimetic solar-driven catalysis, bioenergy, and biomedicine.