Organic Conductive Polymer Research Articles

Conductive phthalocyanine-based porous organic polymer as sensing platform for rapid determination of vanillin.

Vanillin (Van) is widely utilized in processed foods and medicines for its appealing scent and multiple therapeutic benefits. However, its overconsumption poses a risk to public health, making its quantification essential for ensuring food and medicine safety and quality. This study introduces a stable and conductive phthalocyanine-based porous organic polymer (NiPc-CC POP), synthesized through a straightforward electrophilic substitution of nickel tetra-amine phthalocyanine (NiTAPc) with cyanuric chloride (CC). Appropriate characterization techniques were employed to determine the morphologies and structures of the synthesized materials. Furthermore, the NiPc-CC POP was applied to devise a sensitive Van detection method. Leveraging the high electrocatalytic activity of NiPc-CC POP toward Van oxidation, a linear response of 0.15-32 μmol L-1 was achieved, along with an exceptional detection limit of 0.10 μmol L-1. The sensor demonstrated high selectivity and stability. Samples of human serum and tablets spiked with Van were analyzed, yielding satisfactory recoveries. Consequently, this work contributes to the advancement of sensitive detection platforms for Van at minimal concentrations.

Response surface optimization and finite element homogenization study of the effective elastic modulus and electrical conductivity of MXene‐polypyrrole hybrid nanocomposite as electrode material for electronic energy storage devices

AbstractElectrical energy storage devices are crucial for energy storage and distribution purposes. MXene (MX), a 2D material, and conductive organic polymers, such as polypyrrole (PPy), have been widely used as electrode material in electronic energy storage devices. This work calculated the elastic modulus and the electrical conductivity of a MX/PPy nanocomposite electrode using a finite element model. Response Surface Methodology (RSM) was used to optimize the electrical conductivity and elastic modulus response variables based on the finite element (FE) simulation findings. By assigning appropriate weights to these response factors in the optimization technique, the impacts of mass fraction and aspect ratio (AR) of MX inclusion on the electrical conductivity values and elastic modulus of the electrode were analyzed. When compared to the experimental findings, the results demonstrated that the suggested finite element model could provide a satisfactory estimate of the electrical conductivity and elastic modulus of the electrodes made of MX and PPy. However, these response variables might be optimized by using the response surface approach. Therefore, when RSM was employed, both electrical conductivity and Youngs modulus could be adjusted to close to their respective maximum optimal values, with a predicted electrical conductivity of 474.33 S/m and an elastic modulus of 3.24 GPa, at 50% mass fraction of the MX and the AR of 0.2. Based on these results, if a MX/PPy nanocomposite electrode could be built to achieve this modulus and electrical conductivity, such electrode would be a viable material for metal‐ion batteries.

General synthesis of hybrid electrodes with vertical multistage pore-arrays via biphasic interfacial assembly for favorable electrochemical sensing

• 1. Biphasic interfacial assembly method was addressed to optimize the hybrid electrodes. • 2. The typical product of CC/MMPCA presented multistaged sizes from ca. 10 to 250 nm. • 3. The CC/MMPCA-based sensor showed high selectivity and ultra-low LOD (0.27 µM) to DA. • 4. Achieving successful extension to other substrates for rapid and in situ detection. Hybrid electrodes based on conductive inorganic substrates and organic porous structured polymer have attracted significantly scientific and technological interests in numerous areas including electrochemical sensors, catalysis, and energy storage due to their excellent functionality of good permeability to the inner host. The mesoscopic channels, however, pose a problem because their potential applications require mass transport within them, so they are limited by the undesirable and finite structure of mesoscopic channels due to the immense synthetic difficulties. In this study, we demonstrate a facile interfacial assembly strategy for fabricating hybrid electrodes with highly accessible nanochannels on carbon cloth (CC), called macroporous/mesoporous polymer carbon arrays (MMPCA), where the multistage pores size extremely wide from ca. 10 to 250 nm. Owing to these vertically irregular, permeable and multistage channels, electrochemical sensors based on the MMPCA exhibit a low limit of detection (LOD, 0.27 µM) and nice sensitivity (0.545 µA µM -1 cm -2 ) in dopamine (DA) detection. This strategy creates opportunities to controllably tailor the interfacial assembly of multistage mesoporous nanounits on diverse conductive substrate towards versatile applications and underscores the importance of structural alignments for advanced technologies, which could be applied to various fields related to mass transportation and electronic signal transmission.

Fundamental aspects of organic conductive polymers as electrodes

Conductive polymers have gained a significant place among electrode materials for electrochemical sensors and energy storage devices. The latest developments in the targeted modification of the polymers' properties and thin-film microstructure predispose them further to wide applications in this field. The advantages and shortcomings of compositing conducting polymers with metal nanoparticles and 2D materials (graphene and its derivatives, MXenes, MOFs) in electrochemical sensors and supercapacitors are summarized based on selected works. Some challenges for further research are also mentioned briefly.

Hydrogen Evolution Reaction By Metal-Free Poly-Neutral Red Electrocatalyst

While electric power supply by renewable sources such as solar and wind has become viable for their significant cost reduction, its intermittency demands urgent development of large scale storage technologies. Although conversion of electrical energy into storable hydrogen via electrolysis of water is ideal, noble metals and their oxides are used as electrocatalysts for their activities and stabilities. Alternative electrocatalysts out of abundant elements are needed for sustainable technological development.Recently, some metal-free organic conductive polymers with hydrogen-bonding capabilities were found to exhibit high electrocatalytic activities towards hydrogen evolution reaction (HER) [1,2]. We have succeeded electropolymerization of neutral red (NR) resulting in a formation of conductive poly-NR (PNR) that shows a relatively high HER catalytic activity [3]. PNR possesses hydrogen-bonding N atoms as annelated in the phenazine aromatic system as well as those in the amino substituents. Electrochemical analysis combined with in situ spectroscopy as well as DFT calculation was performed to clarify the mechanism and kinetics of HER electrocatalysis by PNR.This films of PNR were obtained by electropolymerization on F-doped SnO2 coated conductive glass (FTO, Asahi Glass) and SIGRATHERM® GFA5 Carbon felt with potential cycling between -0.2 and 1.2 V (vs. Ag/AgCl) at 50 mV s-1 for 50 times in a 5 mM NR - 0.1 M H2SO4 aqueous solution under N2. Polyaniline (PANI) was also obtained by the same method for comparison. The HER catalysis was evaluated by linear sweep voltammetry (LSV) in a 1 M trifluoromethanesulfonic acid (TfOH) under N2. The film samples were characterized by Fourier transform infrared spectroscopy (FT-IR), UV-visible spectroscopy. In-situ UV-visible spectroelectrochemical monitoring of the reaction intermediate was carried out to determine the rate of HER.PNR undergoes a pseudo-reversible reduction that shifts -61.8 mV/pH under acidic conditions and HER takes off right at this point (Fig. 1, a). Coupling of the same number of protons / electrons is expected as the electrochemical stoichometry from the observed Nernstian relationship, namely, resulting in a singly reduced PNR-H or doubly reduced PNR-H2 as depicted in Fig. 1 b. Protonation of N atoms was reasonably expected and also supported by the DFT calculation. The hydrogen atoms stabilized in the reaction intermediate can be associated to release H2 (Tafel mechanism) to complete the cycle of electrocatalysis of HER.Reduction of PNR in fact is associated with a color change. The broad reddish absorption of PNR peaking at around 500 nm attenuates to change the color to a pale yellow by constantly applying -0.15 V vs. RHE to produce PNR-H and/or PNR-H2 state as shown in Fig. 1c. Gradual recovery of the original red PNR was observed under open circuit under N2, associated with the H2 release. Thus, the rate of the spectral change is analyzed to determine the rate of the Tafel process. Pseudo-first order reaction rate law can be applied as proton is abundant and its concentration is constant, so that the rate of HER (r H2) is simply described as the rate of consumption of PNR-H and/or PNR-H2 as, r H2=-dC PNR-H2/dt =-kt (1)The ratio of PNR-H and PNR-H2 as compared to their initial amount (x PNR-red) was defined from the absorbance at 545 nm before and after reduction as, x PNR-red = C PNR-red/C 0-PNR-red = exp (-kt) (2)Good fitting of the experimental data was obtained to yield a pseudo-first order reaction rate constant of 9.98×10-4 s-1 for this rate-limiting step.

3D printing of conductive organic polymers: challenges and opportunities towards dynamic and electrically responsive materials

Since their discovery, conducting polymers have been the subject of longstanding attention for the development of electrically responsive devices. Modern methodologies of manufacturing, including additive manufacturing, are increasingly used in order to create three dimensional systems with controlled architectures. The merging of the two research areas is challenging, given the peculiar macromolecular and chemical characteristics of conductive polymers. We report here an overview about different 3D printing techniques, such as inkjet, extrusion, and light-based printing, for the production of electrically responsive functional materials and devitces for sensing, biosensing or actuative purposes. Recent examples in which the three main classes of conductive polymers, namely, polyaniline, poly(dioxy-3,4-ethylenethiophene) and polypyrrole have been processed with additive manufacturing techniques are sequentially presented.

Adaptable and Wearable Thermocell Based on Stretchable Hydrogel for Body Heat Harvesting

AbstractThe application of traditional inorganic thermoelectric materials to wearable energy harvesters has been hindered by the rigid bulkiness, while flexible organic conductive polymers have been long troubled by their intrinsic low thermopower. An ideal solution that possesses the merits of the two thermoelectric materials is desperately needed for practical application. Here it is demonstrated that a polyacrylamide (PAAm)‐based ultra‐stretchable hydrogel can be selected as a superior candidate matrix for flexible and stretchable thermocells to adapt to the curved surface of the human body and deformation of the ankle. Fe(ClO4)3/Fe(ClO4)2 is selected as n‐type ion pair for their comparable thermoelectric performance to K3[Fe(CN)6]/K4[Fe(CN)6]. The p‐n pair hydrogel electrolytes show a voltage output of 29 mV and current output of 8.5 Am−2 with an average maximum power density of 0.66 mW K−2 m−2 for each p‐n cell (ΔT = 10 K). By integrating with the graphite paper electrode, a body‐conformal and portable thermocell device, employing the hydrogel electrolytes, is fabricated and reached a voltage output of 0.16 V with 14 pairs of p‐n cells (ΔT = 4.1 K). This commercially‐effective blueprint demonstrates the bright future of hydrogel‐based ionic thermocell in daily wearable scenarios.

Fabrication of Electronics by Electrohydrodynamic Jet Printing

AbstractElectrohydrodynamic jet (e‐jet) printing technology overcomes some limitations such as the viscosity and resolution of the traditional ink‐jet printing by breaking surface tension of the droplets with high voltage and the formation of Taylor cone. The technique is becoming more and more popular because it can be widely used in the fabrication of the conductive line of electronics, electrode, transistor, sensor, and other electronics as microelectrode, microlen, and heater. This review provides insight into the effect of the influence factors such as voltage, speed, nozzle, jetting ink characteristics, and the representative conductive materials of the ink as metal nanoparticles (NPs) and carbon materials, or organic conductive polymers on the fabrication of the different electronics by the e‐jet printing technology. Specially, the characteristics of different resultant electronics are compared and the possible mechanisms are analyzed. Finally, the challenge and development trend of the e‐jet printing technology are discussed, which will shed a light on the fabrication of the next‐generation flexible electronics with better performance.

Fe‐VS2 Electrocatalyst with Organic Matrix‐Mediated Electron Transfer for Highly Efficient Nitrogen Fixation

Electrochemical N2 fixation is considered to be a promising alternative to Haber-Bosch technology. Inspired by the composition and structure of natural nitrogenase, Fe-doped VS2 nanosheets were prepared via one-step solvothermal method. The electron transfer system mediated by organic conductive polymer (1-AAQ-PA) was constructed to promote the electron transfer between Fe-VS2 nanosheets and the electrode in electrocatalytic N2 reduction reaction (NRR). The obtained 1-AAQ-PA-Fe-VS2 electrode converted N2 to NH3 with a yield of 31.6 μg h-1 mg-1 at -0.35 V vs. reversible hydrogen electrode and high faradaic efficiency of 23.5 %. The introduction of Fe dopants favored N2 adsorption and activation, while the Li-S bond between Fe-VS2 and Li2 SO4 effectively inhibited hydrogen evolution. The highly efficient electron utilization in the electrocatalytic NRR process was realized using the 1-AAQ-PA as the electron transfer medium. Density functional theory calculations showed that N2 was preferentially adsorbed on Fe and reduced to NH3 via both distal and alternating mechanism.

Fabrication of durable and conductive cotton fabric using silver nanoparticles and PEDOT:PSS through mist polymerization

Conductive cotton fabrics are widely used in electromagnetic shields and soft sensors because of their excellent softness and comfort. Generally, conductive cotton fabrics are prepared by depositing an inorganic conductive coating or an organic conductive polymer coating on them. However, due to the complex structure of cotton fabrics, these conductive coatings easily fall off and fracture under external forces, resulting in a sharp decline in the conductive properties of the finished fabrics. In the present work, L-cysteine was used as a binder to immobilize Ag NPs on cotton fabric. Ag NPs were covered by PEDOT:PSS to prevent them from falling off and cracking. As a result, the surface resistance of finished fabric was arrived at 8.7 Ω/sq. The finished fabric also exhibited excellent electromagnetic shielding effectiveness, with an electromagnetic shielding reached at 27.1 dB. Moreover, the composite coating significantly improved the durability of electrical conductivity and electromagnetic shielding properties of the finished fabric. In addition, mist polymerization was used to retain the inherent properties of the cotton fabric. We believe that the proposed method provides a new direction for the preparation of conductive cotton fabrics with a high stability.

Polyhedral Carbon Anchored on Carbon Nanosheet with Abundant Atomic Fe‐Nx Moieties for Oxygen Reduction

AbstractCarbon‐based single‐atom iron electrocatalysts with nitrogen coordination (CSAIN) have recently shown enormous promise to replace the costly Pt for boosting the cathodic oxygen reduction reaction (ORR) in fuel cells. However, there remains a great challenge to achieve highly efficient CSAIN catalysts for the ORR in acidic electrolytes. Herein, a novel CSAIN catalyst is synthesized by pyrolyzing a precursor mixture consisting of metal–organic framework and conductive polymer hybrid. After pyrolysis at a high temperature, the CSAIN with a structure of carbon nanosheet supported polyhedral carbon is achieved, where the unique structure endows CSAIN with expediting electron transfer and mass transport, as well as largely exposed surface to host atomically dispersed iron active sites. As a result, the optimal CSAIN catalyst shows a high ORR activity with its half‐wave potential of 0.77 V (vs RHE) and a Tafel slope of 74.1 mV dec–1, which are comparable to that of commercial Pt/C catalyst (0.80 V and 81.9 mV dec–1).

Advances in micro‐supercapacitors (MSCs) with high energy density and fast charge‐discharge capabilities for flexible bioelectronic devices—A review

AbstractSupercapacitors are a new brand of high‐performance nanoengineered devices that match the high capacity of batteries for electric energy storage with the ability of dry capacitors for ultra‐fast charging or discharging rates. Thus, supercapacitors are capable of simultaneously providing the high energy‐density and high power‐density, demanded in a plethora of biosensors and portable electronic devices. In this review, a variety of nanomaterials investigated for possible applications in novel supercapacitors have been evaluated including different carbon nanoforms, metal oxides or hydroxides, chalcogenides, carbides and phosphates, as well as organic redox species, conductive polymers, metal‐organic frameworks, MXenes and others. Different strategies for boosting volumetric capacitance, power density and charge or discharge cycling stability of micro‐supercapacitors (MSCs) designed from these materials have been reviewed and their application potential assessed. Special attention has been given to micro‐supercapacitor's designs that are suitable for miniaturization and integration with flexible microcircuits for wearable and implantable biomedical devices, remotely rechargeable sensors, microprocessor‐controlled data processing chips, biomorphic computing, smart phone communication, military, automotive applications and emerging technologies. The different strategies applied for MSCs design and fabrication, including femto‐laser writing, photolithography, screen printing, stamping, inkjet printing, mask patterning and others, have been assessed. The exciting future perspectives of MSCs have been discussed.

Resonance phenomena and impact resistance performance of the organic solar cell under external environmental loading

An organic solar cell is a kind of photovoltaic cell that uses organic electronics, a branch of electronics that presents small organic molecules of conductive organic polymers for charge transport and light absorption until a photovoltaic effect produces electricity from sunlight. Regarding this, a computer simulation is presented to analyze the resonance analysis and dynamic stability of the organic solar cell. For simulating the size effects, the nonlocal strain gradient theory that adds some terms to the displacement and time terms of governing equations is presented. As the first step, the Navier method is applied as the analytical solver of the governing differential equations developed on the foundations to find the dynamics of the design points. The accuracy of the first step is tested and validated by a comparison study with those recorded in the high-quality papers. The results show that viscoelastic foundation, size-dependent parameter, and geometrical parameters can have a marvelous influence on the stability and dynamic deflection of the organic solar cells. The most relevant result is that the effect of size-dependent parameters on the dynamics of the organic cell is more remarkable at the higher value of the thickness of the cell.

Enhanced white light emitting device based on ZnTe nanocrystals and conductive organic polymer by surface excitons

The white organic lighting has been intended device appearing an emission cover lightemitting conductive polymer (Poly (p-phenylene vinylene) (PPV) and poly (p-phenylene sulfide) (PPS)) as a host material for zinc telluride (ZnTe) nanocrystals (NCs) or quantum dots (QDs) and tris-(8-hydroxyquinoline)-aluminum (Alq3) together of titanium oxide (TiO2) thin layer as white light emitters. The white light-emitting electroluminescence (EL) procedure be defined by of three covers deposited successively upon the ITO glasssubstrate surface ITO/PVV: PSS/ZnTe NCs/Alq3 with TiO2/Ni. Current-voltage (I-V) attributes show a strong output current relative to the few voltages (4 V) that are used to produce acceptable white light output performance. The Commission International de l’Eclairage coordinates of the device's emitting light was recognized (X= 0.31, Y= 0.34) which were only slightly changed over a range of applied voltage (4 Volts) and correlated color temperature (CCT) was realized nearly 6250 K. The production of ZnTe NCs lightemitting device with organic polymer hole injection (PVV: PSS) and organic molecules (Alq3 with TiO2) was successful in white-light production.

Redox Polymers for Tissue Engineering.

This review will focus on the targeted design, synthesis and application of redox polymers for use in regenerative medicine and tissue engineering. We define redox polymers to encompass a variety of polymeric materials, from the multifunctional conjugated conducting polymers to graphene and its derivatives, and have been adopted for use in the engineering of several types of stimulus responsive tissues. We will review the fundamental properties of organic conducting polymers (OCPs) and graphene, and how their properties are being tailored to enhance material - biological interfacing. We will highlight the recent development of high-resolution 3D fabrication processes suitable for biomaterials, and how the fabrication of intricate scaffolds at biologically relevant scales is providing exciting opportunities for the application of redox polymers for both in-vitro and in-vivo tissue engineering. We will discuss the application of OCPs in the controlled delivery of bioactive compounds, and the electrical and mechanical stimulation of cells to drive behaviour and processes towards the generation of specific functional tissue. We will highlight the relatively recent advances in the use of graphene and the exploitation of its physicochemical and electrical properties in tissue engineering. Finally, we will look forward at the future of organic conductors in tissue engineering applications, and where the combination of materials development and fabrication processes will next unite to provide future breakthroughs.

Building sp carbon-bridged g-C3N4-based electron donor-π-acceptor unit for efficient photocatalytic water splitting

sp hybrid carbon is emerging as a promising unit for covalent modification of organic frameworks and conductive polymers, and has been widely concerned in conjugated polymer catalysts because it can be used to construct π-electron conjugated system. Herein, we provide a simple and effective post reaction strategy to activate g-C3N4 via coupling reactions. The grafted g-C3N4 exhibits improved light absorption and separation of charges, and better water dispersibility along with increased co-catalyst loading sites, which accelerate photocatalytic hydrogen evolution. Photocatalytic H2 evolution activity of UCN-BTD and UCN-BF, in which terminal amino groups are grafted with 2,1,3-benzothiadiazole,5-(1-propyn-1-yl) or 2,1,3-benzoxadiazole,5-(1-propyn-1-yl), reveals the important role of sp hybrid carbon and electronegativity of the acceptor. The optimized UCN-BTD photocatalyst showed a significant improvement in photocatalytic hydrogen evolution performance (122 μmol·h−1), which is nearly five times of that of the pristine g-C3N4. This work provides insights for the preparation of g-C3N4-based donor-π-acceptor unit constructed with different conjugated structures.

Recent progress in organic Polymers-Composited sulfur materials as cathodes for Lithium-Sulfur battery

• Organic polymer cathode materials for Li-S batteries are reviewed. • Several challenges of organic polymers-based materials are analyzed with respect to their Li-S batteries performance. • The possible further research directions for overcoming the challenges are also proposed. With a theoretical specific capacity of 1675 mAh g −1 and an energy density of 2600 W h g −1 , environmentally friendly lithium-sulfur batteries (LSBs) have been considered to be one of the most promising candidates for the next generation of high energy density storage devices, which are expected to meet the requirements of transportation vehicles and power grid energy storage. However, LSBs still have several technical challenges hindering their practical applications. One of the challenges is the dissolution of the cathode sulfur and polysulfides caused shuttle effect which can significantly reduce their cycle-life. To mitigate the challenges, conductive organic polymers have been explored for holders to encapsulate sulfur and inhibit the dissolution of polysulfides into the electrolyte, as well as increase both the electric and ionic conductivities of the corresponding cathodes. This paper reviews the recent progress in conductive organic polymers-composited sulfur materials as cathodes for LSBs in terms of their synthesis, characterization, functional mechanisms and performance validation/optimization. The reviewed polymers include polyacrylonitrile (PAN), polyaniline (PANI), polythiophene (PTh), polypyrrole (PPy), pypercrosslinked polymers (HCPs), etc. Several technical challenges of these organic polymers-based materials are analyzed with respect to their LSB performance, and several possible further research directions for overcoming the challenges are also proposed for further development toward practical applications.

Achieving Ultralow, Zero, and Inverted Tunneling Attenuation Coefficients in Molecular Wires with Extended Conjugation.

Molecular tunnel junctions are organic devices miniaturized to the molecular scale. They serve as a versatile toolbox that can systematically examine charge transport behaviors at the atomic level. The electrical conductance of the molecular wire that bridges the two electrodes in a junction is significantly influenced by its chemical structure, and an intrinsically poor conductance is a major barrier for practical applications toward integrating individual molecules into electronic circuitry. Therefore, highly conjugated molecular wires are attractive as active components for the next-generation electronic devices, owing to the narrow highest occupied molecular orbital-lowest occupied molecular orbital gaps provided by their extended π-building blocks. This article aims to highlight the significance of highly conductive molecular wires in molecular electronics, the structures of which are inspired from conductive organic polymers, and presents a body of discussion on molecular wires exhibiting ultralow, zero, or inverted attenuation of tunneling probability at different lengths, along with future directions.

Conducting Poly-Adenine Electrocatalyst for Hydrogen Evolution Reaction

1. Introduction Hydrogen is a promising energy carrier, but is currently produced by steam reforming of fossil fuels to discharge CO2. Water splitting by electricity from renewable resources is an ideal solution. However, expensive and rare metals such as Pt and Ru are needed as electrocatalysts for their high activity and durability.We have recently found that metal-free organic conductive polymer made by polymerization of guanine (PG) exhibits a high catalytic activity for hydrogen evolution reaction (HER) close to that of Pt.1,2,3 Hydrogen bonding sites in PG are supposed to stabilize the reaction intermediates. It is also interesting that a nucleic acid as one of the key components of DNA has such properties for HER catalysis.In this work, we have explored other nucleic acids, namely, adenine, cytosine and thymine for their capabilities of polymerization by oxidative chemical vapor deposition (oCVD) and HER activities. 2. Experimental oCVD was carried out in a 3-zone heating quartz tubular furnace, in which 0.5 g of monomer (set to 300~360°C depending on melting points), oxidant (mixture of 0.5 mL sulfuric acid and 0.5 g sodium sulfate, 360°C) and carbon felt (CF) substrate (1.5 cm × 2.5 cm, Jing Long Te Tan, 360°C) were put under N2 stream (3 L/min). The deposition was maintained for 30 minutes after the set temperatures were reached and then allowed to cool down. FT-IR spectra were measured to check formation of conductive polymers. Linear sweep voltammetry (LSV) was performed at 10 mV/s on the polymer coated CF electrodes in a 0.1 M sulfuric acid under N2 to evaluate overvoltage for hydrogen evolution reaction (HER) at 10 mA/cm2. 3. Results and Discussion A black layer was formed by oCVD of adenine. Its FT-IR spectrum exhibited broad peaks around 3000 cm-1, indicative of hydrogen bonds, as well as several strong peaks below 1000 cm-1, which shows presence of free charge carriers to evoke infrared-activated vibration (IRAV). Since similar features were observed in the FT-IR of PG,2 formation of conductive poly-adenine (PA) is reasonably expected. While oCVD of cytosine also yielded similar black film, suggesting formation of PC, that of thymine did not afford any product on the substrate, despite several trials to change temperatures and other deposition conditions. The difference can be reasoned as adenine and cytosine bear cross-linkable amino groups, whereas thymine does not have one.Preliminary electrochemical study revealed an overvoltage of CA. 700mV, far larger than that of PG (290 mV).2 While PG has a hydrogen donating -NH group and a hydrogen accepting ketone group in α-position, PA does have an -NH group but not a ketone. Such difference in the structure of hydrogen bonding site is a possible reason for the large difference of the catalytic activity. Further studies about the HER electrocatalysis are under investigation.

The Study of Synthesis Mechanism of Poly-Neutral Red and Its Electrocatalytic Property

１． Intention Concentration of carbon dioxide (CO2) in the atmosphere has steadily increased since industrial revolution. Despite the recent significant cost reduction of renewable electricity by solar and wind, their intermittency hinders the total shift to renewable energy. It is urgently needed to develop technologies for fast conversion of electrical energy into storable chemical energy by electrolysis, e.g., by water splitting and CO2 reduction. Stable and high-performance electrocatalysts are essential but must be developed without depending on precious metals for the real use and sustainability of the technology. Recently, we have demonstrated high and stable electrocatalytic properties of conductive organic polymers, such as polydopamine (PDA) and polyguanine (PGA) for hydrogen evolution reaction (HER) and CO2 reduction reaction (CO2RR)1,2). Hydrogen bonding N and O atoms introduced to these polymers are expected to stabilize the reaction intermediates for their high catalytic activities. In this study, a phenazine dye, neutral red (NR) was employed as the monomer to obtain a metal-free catalyst. NR bears many amino functions to make it electropolymerizable just like poly-aniline (electropolymerization deposition, to be called EPD). Also, oxidative chemical vapor deposition (oCVD) was employed to obtain PNR. Synthesis, characterization and comparison of the catalytic activities of PNR by EPD and oCVD are discussed. ２． Experiment EPD of PNR onto carbon felt (CF) was carried out by cycling potential between -1 and +1 V vs. Ag/AgCl for 100 cycles in an aqueous solution containing 0.2 mmol/L NR and 0.5 mol/L KNO3 (pH 5) at 50 mV/s. oCVD of PNR was performed in a three-zone quartz tube furnace under N2 flow, while setting the temperature for NR, sulfuric acid and CF at 375, 220 and 100ºC, respectively, for 240 min. PNR-modified as well as bare CF electrodes were measured under N2 and CO2 in a 1 M KNO3 (pH 7) for their catalytic activities for HER and CO2RR. ３． Result While bare carbon felt (CF) electrode does not show any catalytic activity towards CO2RR, showing about -3 mA cm-2 current at –1 V vs. Ag/AgCl, supposedly dominated by that for HER, the PNR coated CFs show enhanced current (Fig. 1a). That by EPD gives about -5 and -6 mA under N2 and CO2, respectively, indicating its moderate catalytic activity for HER and CO2RR. PNR prepared by oCVD, on the other hand, gives -6 and -12 mA, to demonstrate its superior activity, especially for CO2RR. Chronoamperogram measured during long term electrolysis for 17 h at the oCVD PNR electrode indicates reasonable stability of the catalysis (Fig 1b). These results already nicely confirm catalytic activity of PNR for its conductivity and hydrogen-bonding ability. H. Coskun et al., Sci. Adv. 3, e1700686 (2017).H. Coskun et al., Adv. Mater. Interf. 10, 1901364 (2019). Figure 1