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. 2019 Jan 14;12:204–215. doi: 10.1016/j.isci.2019.01.016

Nontemplating Porous Carbon Material from Polyphosphamide Resin for Supercapacitors

Bin-Hai Cheng 1,2, Fan-Xin Zeng 2, Wen-Jing Chen 2, Hui-Yuan Cheng 2, Raymond J Zeng 1,2, Hong Jiang 2,3,∗
PMCID: PMC6354840  PMID: 30703734

Summary

The nontemplating preparation of porous carbon materials by using specially designed polymer precursors for supercapacitor is attracting considerable research attention because of the more controllable frame structure and easier processes than templating methods. Herein, a deliberately designed cross-linking polyphosphamide resin with defined N and P structure is synthesized and then carbonized to obtain porous carbon material. The as-obtained porous carbon material has a specific surface area of 2,620 m2 g−1, high porosity of 1.49 cm3 g−1, and well-distributed micro/mesoporous carbon structure. Different from activation by post-added NH4H2PO4, the confined N and P in the polymer frame are confirmed to play an important role in pore structure development by forming in situ highly dispersed NH4H2PO4 during carbonization. When evaluated as the electrode material for supercapacitors, the polyphosphamide-resin-based porous carbon material demonstrates excellent capacitance (440 F g−1 under 0.5 A g−1) and high stability (retention of 93% over 10,000 cycles).

Subject Areas: Electrical Property, Polymers, Nanomaterials, Energy Materials

Graphical Abstract

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Highlights

  • •

    A cross-linking polyphosphamide resin with defined N and P structure is synthesized

  • •

    A PCM prepared form the special resin exhibited high supercapacitor performance

  • •

    The pore formation mechanism of the PCM was investigated

Electrical Property; Polymers; Nanomaterials; Energy Materials

Introduction

With the depletion of conventional energy resources, green and sustainable energy conversion and storage technologies are attracting more and more attention. Among various energy storage devices, supercapacitors have their advantages of high charge-discharge rate, long cycle life, high energy conversion efficiency, etc. (Wang et al., 2012). According to the energy storage mechanisms, supercapacitors can be categorized into electrical double-layer capacitors (EDLCs) and pseudocapacitors (Salanne et al., 2016). EDLCs store energy through ion adsorption-desorption at the electrode-electrolyte interfaces. The typical materials for EDLCs always have high specific surface area (SSA), such as porous carbon (Yao et al., 2018), carbon nanotube (Yu et al., 2014), and graphene (Strauss et al., 2018). Pseudocapacitors store energy by reversible faradaic reactions of the electrode materials, such as Ni(OH)2 (Su et al., 2014), MnO2 (Wang et al., 2015), and V2O5 (Wang et al., 2018a). Up to now, EDLCs still hold the dominant market position owing to their low cost and high reliability.

Porous carbon materials (PCMs) are widely used as electrode materials in supercapacitors, especially EDLCs, owing to their stable physical and chemical properties, large SSA, controllable pore structure, high electronic conductivity, and low cost (Liu et al., 2017, Simon and Gogotsi, 2008, Zhai et al., 2011, Zhang and Zhao, 2009). The capacitance of PCM-based supercapacitors is mainly determined by the SSA and pore structure of PCMs, providing ion storage interface and facilitating the ion transportation, respectively (Chmiola et al., 2006a, Pandolfo and Hollenkamp, 2006). Therefore much research has been devoted to optimize the pore structure by preparing ordered and hierarchical (micropores and mesopores) PCMs on the premise of remaining large SSA to enhance the EDLC capacity (Kondrat et al., 2012, Largeot et al., 2008, Qie et al., 2013, Tran and Kalra, 2013). Although metal-organic frameworks (Hu et al., 2010) and metal carbides (Chmiola et al., 2006b) have been used to prepare pore-controllable PCMs, organic polymers are promising precursors because they can be handily designed and synthesized with specific structures and composition; these features are important to obtain PCMs with the desired pore structure (Dutta et al., 2014, Wei et al., 2013, Xu et al., 2013, Zhong et al., 2012).

Polymerization of monomers for preparing organic polymers provides the possibility of tuning the final structures, during which monomers may be restricted to the specific space for in situ polymerization or self-assembly. For instance, Böttger-Hiller et al. used spherical SiO2 particles as hard templates to allow in situ monomer polymerization and prepared hollow carbon spheres with porous shell by carbonization and washing of the templates (Böttger-Hiller et al., 2013). Using surfactants or block copolymers as soft templating can direct the polymerization of monomers, and after drying and carbonization, PCMs can be obtained (Chuenchom et al., 2012). For instance, block copolymers, such as Pluronic F-127 (EO106PO70EO106), are commonly used as structure-directing agents for the self-assembly of monomers (Hasegawa et al., 2016, Wang et al., 2018b, Xiong et al., 2017). Liang et al. reported that, by changing the mixture of F127, phloroglucinol, and formaldehyde and the processing conditions, different forms of fibers, sheets, films, and monoliths can be readily synthesized (Liang and Dai, 2006). Estevez et al. reported a dual-templating and post-activation strategy to prepare hierarchical porous carbon (Estevez et al., 2013). Combined ice-template and colloidal silica followed by physical activation was applied to generate interconnected macro-, meso-, and microporosity. However, most of the templates are rather expensive and nonrenewable, which limits their application.

In recent years, several studies focused on developing new methods from direct carbonization of special polymers without using any template (Hu et al., 2012, Zhang et al., 2013, Zhu et al., 2015). Porous structure can be formed by regulating the cross-linking style of the polymer or inserting specific elements into the framework. For instance, Puthusseri et al. reported a nontemplating method to synthesize interconnected microporous carbon material by direct pyrolysis of poly (acrylamide-co-acrylic acid) potassium salt without any additional activation. During the pyrolysis, the potassium in the polymer reacted with the carbon to form K2CO3, which creates pores in the carbon framework (Puthusseri et al., 2014). Sevilla et al. reported similar results by using potassium citrate as the precursor (Sevilla and Fuertes, 2014). Apart from K2CO3, chemical compounds, such as KOH, NH3, and NH4H2PO4, were also helpful in the formation of porous carbon (Krüner et al., 2018, Li et al., 2010, Wang and Kaskel, 2012, Zhou et al., 2015).

In this study, we proposed a nontemplating method to prepare PCM with high capacitance. We first designed and synthesized a hyper-cross-linked N, P-rich polymer containing the P–N groups, denoted as polyphosphamide resin (PAR). Hyper-cross-linked N, P-rich polymer with hierarchical framework can not only facilitate the formation of well-defined pore structure but also increase the SSA by activation of the formed N, P species (such as NH3 and NH4H2PO4). Afterward, the PAR was pyrolyzed and post-activated to prepare PCMs. The properties of PAR and the as-prepared PCM were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectrum, scanning electron microscopy (SEM), etc. The electrochemical capacitance performance of the as-obtained PCMs was evaluated both in the three-electrode and two-electrode systems. The role of N, P in improving the PCM performance was also investigated.

Results

Preparation of Polyphosphamide Resin

PAR was prepared according to our previous work (Zeng et al., 2011). The synthetic route of the PAR is shown in Scheme 1.

Scheme 1.

Scheme 1

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Scheme for the PAR Synthesis

In the synthesis of PAR, N–P bonds were formed to link the phosphoryl trichloride and hexane-1,6-diamine. Phosphoryl trichloride acted as a center to connect three molecules of hexane-1,6-diamine, and the other head of hexane-1,6-diamine was bonded to another phosphoryl trichloride. Thus, a branch-like network grew. Therefore the O=P–(N–C)3 structures were well-dispersed as nodes in the PAR network, as shown in Figure 1.

Figure 1.

Figure 1

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Simulated Molecular Model of PAR

(A) Formation of O=P–(N–C)3 node with one phosphoryl trichloride molecule and three hexane-1,6-diamine molecules.

(B) Possible structural unit of PAR.

(C) Simulated molecular structure of PAR. Atoms involved in simulation: carbon, gray; nitrogen, blue; oxygen, red; phosphorus, pink; and hydrogen, white.

The FTIR spectrum of PAR is shown in Figure 2A. The broad band at 3,422 cm−1 indicated the existence of N–H. The doublet peaks occurring at 2,930 and 2,858 cm−1 were ascribed to the symmetric and asymmetric stretchings of alkyl C–H. The band at 1,640 cm−1 was the stretching of P=O. The peaks at 1,546 and 1,463 cm−1 were the deformation vibration of N–H and bending vibration of C–H, respectively. The peaks at 1,267 and 1,096 cm−1 were attributed to the symmetric and asymmetric stretching vibrations of C–N. Notably, the peak at 982 cm−1 indicated the presence of N–P. Furthermore, the XPS spectra shown in Figure S2 demonstrated the existence of N–P bonds. All these peaks found in the FTIR spectrum and XPS spectra suggested that the phosphoramide structure of the resin was formed, consistent with the initial design.

Figure 2.

Figure 2

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Materials Characterization of PAR

(A) FTIR spectrum of the PAR.

(B) TG-differential scanning calorimeter (DSC) curves of the PAR.

The thermal degradation behavior of PAR is shown in Figure 2B. Two major degradation peaks are shown in the differential thermal analysis curve (red line). One is from ∼381°C to 495°C, with 18.6% loss of the total weight attributed to the decomposition of the P–N, C–N, and P=O groups. The other is from ∼495°C to 779°C, with 52.1% loss of the total weight due to polymer carbonization (e.g., the cleavage of C–H and C–C bonds) to form the carbon framework.

Physicochemical Properties of PCMs

Based on the thermogravimetric analysis (TGA), the PAR was pyrolyzed under an Ar atmosphere to prepare PCMPAR. The morphology and structure of PCMPAR were first examined by SEM and transmission electron microscopy (TEM). The SEM image shows that PCMPAR has rough surface with multiple micropores (Figure 3A). The TEM image exhibits large number of micropores in the inner structure of the material (Figures 3B and S3), indicating that it is a porous material. The porous nature of PCMPAR can enhance the performance of supercapacitor (Hou et al., 2015, Huang et al., 2016, Tian et al., 2015). N2 adsorption-desorption method was used to analyze the SSA and pore texture of the PCMs. In Figure 3C, compared with PCMPFR, PCMPAR and PCMPFR+NP exhibit a significant increase in volume when P/P0 increases from 0 to 0.3. This phenomenon suggests that the curves are between types I and IV (IUPAC classification), which is attributed to the presence of certain mesopores in the materials (Tao et al., 2006). The result can also be proved by pore size distributions (Figure 3D), which indicates that all the PCMs possess a certain fraction of mesopores (>2 nm). The figure clearly shows that the micropores of PCMs concentrated at 1–3 nm along with a small proportion at approximately 0.5 nm. Notably, the proportion of mesopores showed an order of PCMPAR>PCMPFR+NP>PCMPFR. The Brunauer–Emmett–Teller (BET) SSAs of PCMPAR, PCMPFR, and PCMPFR+NP were 2,620, 2,233, and 3,062 m2 g−1, respectively. The SSA, pore volume, and average pore size of the PCMs are summarized in Table 1.

Figure 3.

Figure 3

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Characterization of the PCMs

(A) SEM image of PCMPAR (scale bar, 100 nm).

(B) TEM image of PCMPAR (scale bar, 100 nm).

(C) N2 adsorption and desorption isotherms of PCMPAR, PCMPFR, and PCMPFR+NP.

(D) Pore size distributions of PCMPAR, PCMPFR, and PCMPFR+NP.

Table 1.

Textural and Chemical Properties of PCMPAR, PCMPFR, and PCMPFR+NP

Sample Code SBET (m2 g−1) VPa (cm3 g−1) Pore Size (nm) Elemental Analysis
 XPS Analysis
N (wt %) P (wt %) N (at%) P (at%)
PCMPAR 2,620 1.49 2.3 1.07 0 1.14 0.08
PCMPFR 2,233 1.19 2.1 0.80 0 1.09 0
PCMPFR+NP 3,062 1.68 2.2 0.27 0 0.60 0.16
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a

Pore volume determined at P/P0 = 0.99.

Influence of the Precursor on the Formation of PCMs

To reveal the roles of nitrogen and phosphorus in the formation of special pore structure of PCMPAR, PFR was selected as a common precursor to fabricate PCMPFR, which contains no nitrogen and phosphorus. The transformation of N and P during the entire process was investigated to explore their effect on the formation of PCMs. The change of P content during the porous carbon preparation is shown in Figure 4A. Briefly, 13.2 wt % P in original PAR concentrated to 18.8 wt % in PAR-char after pre-carbonization and further decreased to 0 wt % after activation (Table 1). This result can also be proved by the XPS result (Figures 4C and 4D). The high-resolution XPS spectra of N 1s were fitted and presented in Figure 4E. The peak at 401.0 eV of PCMPAR and PCMPFR+NP can be ascribed to the binding energy of graphitic-N, whereas the peak at 399.3, 401.0, and 401.9 eV of PCMPFR can be fitted to pyrrolic-N, graphitic-N (eV), and oxided-N, respectively (Sun et al., 2018). The content of the doped-N of all PCMs are around or below 1 atom % (1.14 atom % for PCMPAR, 1.09 atom % for PCMPFR, and 0.60 atom % for PCMPFR+NP). Therefore we concluded that the low content of doped N has little influence on the capacitance performance, which is similar to the effect of phosphorus. X-ray diffraction (XRD) results showed that after PAR pre-carbonization, the nitrogen and phosphorus were transformed to NH4H2PO4 in PAR-char. NH4H2PO4 may act as an activating agent to create pores.

Figure 4.

Figure 4

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Analysis of Nitrogen and Phosphorus during Thermal Treatment

(A) Transformation of P content during the material preparation.

(B) XRD patterns of PAR and PAR-char.

(C) XPS survey spectra of PCMPAR, PCMPFR, and PCMPFR+NP.

(D) XPS P 2p spectra of PCMPAR, PCMPFR, and PCMPFR+NP.

(E) XPS N 1s spectra of PCMPAR, PCMPFR, and PCMPFR+NP.

PCMPAR had fine textural properties with high nitrogen uptakes and a BET surface area of 2,620 m2 g−1, which was higher than that of PCMPFR (2,233 m2 g−1). Moreover, PCMPAR had more mesopores than PCMPFR, as proven by the pore size distribution and the average pore diameters (2.3 nm of PCMPAR and 2.1 nm of PCMPFR). To verify the importance of chemically bonded N and P in PAR, equal weight of NH4H2PO4 was added in PFR-char for the following activation (PFR-char:NH4H2PO4:KOH = 0.59:0.41:4). The results showed that the introduction of NH4H2PO4 to the PFR can significantly improve the micropore formation. Thus the pore volume (1.68 cm3 g−1) and SSA (3,062 m2 g−1) of PCMPFR+NP increased, which was 1.37 times higher than that of PCMPFR and 1.17 times higher than that of PCMPAR. Therefore both external and in situ NH4H2PO4 acted as an activating agent to create pores (Li et al., 2010, Xu et al., 2017). However, the in situ NH4H2PO4 may be helpful in forming mesopores than externally added NH4H2PO4. It can be clearly found that PCMPAR has a higher proportion of mesopores/micropores than PCMPFR+NP (Figure 4D). This condition may affect the capacitance performance of PCM.

There are no sharp peaks in the XRD pattern of PCMPAR, PCMPFR, and PCMPFR+NP, indicating the amorphous state of carbon in PCMs (Figure S4). Raman spectra of the PCMs are shown in Figure S5. Two characteristic peaks at 1,340 and 1,580 cm−1 are assigned to the defect-induced band (D) and graphitic band (G), respectively (Wang et al., 2018c). The disorder degree of the PCMs can be generally described by the intensity ratio between the D and G bands (ID/IG). The ID/IG of PCMPAR, PCMPFR, and PCMPFR+NP were 0.90, 0.98, and 0.92, respectively. The slightly lower ID/IG of PCMPAR indicated that it had lower disorder degree and higher degree of graphitization, which was beneficial to improve the electric conductivity.

Explanation of the Effect of N and P

The role of N, P in the formation of porous carbon was proposed (Figure 5). In pre-carbonization, N–P and C–N bonds decomposed, and part of the N, P combined with H to form NH3 and PH3. The others combined with H and O and transformed to NH4H2PO4. The polymer framework was partially carbonized to form a NH4H2PO4-decorated raw char. During the activation process, KOH could firstly react with the NH4H2PO4 as follows: NH4H2PO4 + 3KOH = NH3↑+ K3PO4 + 3H2O↑. To confirm this hypothesis, we conducted Thermogravimetric Analysis and Fourier Transform infrared spectroscopy (TG-FTIR) characterizations of PAR samples. The pre-carbonized PAR (PAR-char) and the KOH-added sample (PAR-char + KOH) were first analyzed with a TG analyzer, and the released gaseous products were online analyzed by an FTIR spectrometer. TG-differential thermal gravity (DTG) results show that PAR-char + KOH has a significant weight loss in the range of 100°C –400°C, which is rather different from PAR-char (>600°C). Given that PAR-char was already pre-carbonized at 500°C and exhibited no apparent weight loss (Figure S6), the weight loss of PAR-char + KOH should be caused by the reactions between NH4H2PO4 in PAR-char and KOH during carbonization and released gaseous products. Furthermore, FTIR results show that H2O, NH3, and CO2 were the main gaseous products of PAR-char + KOH, whereas little H2O and NH3 were released from PAR-char (Figures 5B–5E and S7), demonstrating that the reaction of NH4H2PO4 in PAR-char and KOH occurred. Therefore the NH4H2PO4 in PAR-char is not easy to decompose below 500°C, but can react with KOH during the heating process. In addition, the main gaseous products (H2O, NH3, and CO2) as well as K3PO4 and the excess KOH can all act as activating agents to improve the porosity of carbon substrate. Besides, the pre-carbonized PAR was just physically mixed with KOH powder, thus the NH4H2PO4 embedded in carbon was partially in contact with KOH. Importantly, the special N–P structure of PAR formed highly dispersed NH4H2PO4 and thus resulted in the development of well-distributed micro/mesopores, which is beneficial to improve the capacitance performance (Li et al., 2014, Zheng et al., 2015).

Figure 5.

Figure 5

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Mechanism of the Formation of Micro/Mesopores

(A) Scheme for PCMPAR synthesis from PAR, and the possible roles played by N and P during the formation of micro/mesopores.

(B) 3D infrared spectrum of gaseous compounds released during pyrolysis of PAR-char + KOH.

(C) 3D infrared spectrum of gaseous compounds released during pyrolysis of PAR-char.

(D) FTIR spectra of pyrolysis products of PAR-char + KOH at selected temperatures.

(E) FTIR spectra of pyrolysis products of PAR-char at selected temperatures.

Electrochemical Performance of the PCMs

The electrochemical performance of the PCMs was investigated with CV and GCD measurements. The cyclic voltammetry (CV) curves and galvanostatical charge–discharge (GCD) profiles of PCMs are shown in Figure S8. The CV curves of PCMPAR under wide scan rates from 5 mV s−1 to 100 mV s−1 showed a similarly rectangular and symmetric shape (Figure S8A). Importantly, the CV curves of PCMPAR still maintained a rectangular shape even at a sweep rate of 100 mV s−1 and an inapparent reduction in the CV area. This phenomenon indicated that PCMPAR has a fine ion transporting and accessible surface area. The PCMPFR and PCMPFR+NP had similar CV shapes with PCMPAR but suffered an area distortion at a high scan rate and a prominent area reduction with the increase in scan rate. This condition indicated a poor capacitance performance of PCMPFR and PCMPFR+NP at high charge-discharge rate. Instead of the typical rectangular shape, a region of reversible pseudofaradaic reaction can be observed at about −0.5 V in the CV curves. In addition, the approximate triangular charge-discharge profiles and their slightly nonlinear characteristic exhibited the primary EDLC performance and additional pseudocapacitance performance (Figure S8B). The pseudocapacitance can be attributed to the high oxygen content (7%–8%) of the PCMs (Table S1) (Guo et al., 2014, Liu et al., 2018, Tang et al., 2017).

CV curves of the PCMs at scan rate of 50 mV s−1 show that the specific capacitance has an order of PCMPAR>PCMPFR+NP>PCMPFR (Figure 6A). The result can also be proved by the GCD profiles under current density of 5 A g−1 (Figure 6B). The GCD measurements were performed under different current densities to assess specific capacitance (Figure 6C). The PCMPAR showed a high specific capacitance of 440 F g−1 under a current density of 0.5 A g−1 and still maintained at 278 F g−1 at a high current density of 20 A g−1. This PCM material shows a competitive performance among carbon-based supercapacitor electrodes (Table S2). As a comparison, the specific capacitances of PCMPFR and PCMPFR+NP are also listed in Figure 6C. PCMPFR had the lowest specific capacitance (348 F g−1 at 0.5 A g−1 and 150 F g−1 at 20 A g−1) attributed to the lowest SSA (2,233 m2 g−1) because the specific capacitance of EDLC mainly depended on the SSA and porosity characteristics of electrode materials. PCMPFR+NP (3,062 m2 g−1) had larger SSA than PCMPAR (2,620 m2 g−1), but the specific capacitance of PCMPFR+NP was not higher than that of PCMPAR under overall current densities. When the current density was below 1 A g−1, PCMPFR+NP exhibited higher specific capacitance than PCMPAR. However, when the current density was above 1 A g−1, PCMPAR showed high specific capacitance. At low charge-discharge rate, ions from the electrolyte had enough time to accumulate on the electrode surface. Therefore, SSA dominated the capacitance performance. Meanwhile, at high charge-discharge rate, ions cannot be delivered to the surface in time owing to the limitation of the pore structure. This phenomenon indicated that SSA was not finely utilized. As a result, the pore characteristics and the accessible surface area determined the specific capacitance at high charge-discharge rate. Researchers found hierarchical porous microstructures, namely, proper macroporous, mesoporous, and microporous distributions, which are favorable for the diffusion of electrolyte ions, thus leading to a high-rate electrochemical capacitance (Li et al., 2013, Zhang et al., 2016, Zheng et al., 2010). The pore size distribution showed that PCMPAR has more mesopores than PCMPFR and PCMPFR+NP (Figure 2D). With the increase of the proportion of mesopores, PCMPAR can provide a sufficient electrode-electrolyte interface for the accumulation of ions. Thus capacitance performance was improved.

Figure 6.

Figure 6

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Electrochemical Characterization of the PCMs in Three-Electrode System

(A) CV curves of the PCMs at scan rate of 50 mV s−1.

(B) GCD profiles of the PCMs under current density of 5 A g−1.

(C) Specific capacitance of the PCMs calculated by GCD profiles.

(D) EIS plots of the PCMs.

Electrochemical impedance spectroscopy (EIS) was performed to further understand the ion or charge transport of the PCMs. As shown in Figure 6D, in the low-frequency region, the PCMs showed almost vertical curves, wherein PCMPAR had the highest slope. This phenomenon indicated the nearly ideal EDLC behavior and the small equivalent diffusion resistance. In the high-frequency region (inset in Figure 6D), the intercept on the real axis presented low values (<0.4 Ω). This finding corresponded to low equivalent series resistances and indicated the excellent conductivity of the PCMs in aqueous electrolyte system. From the high- to low-frequency region, the low interfacial charge transfer resistances calculated from the diameter of the semicircle were 0.09 Ω of PCMPAR, 0.29 Ω of PCMPFR, and 0.10 Ω of PCMPFR+NP. The EIS results showed that PCMPAR had smaller contact resistance among the electrode materials and electrolyte ions, indicating lower charge transfer resistance on the electrode surface. Furthermore, the cycling stability of the PCMPAR was evaluated by long-term CV cycling measurement at a scan rate of 50 mV s−1. The result showed that PCMPAR has fine capacitance retention of 93% over 10,000 cycles (Figure S9). Besides, PCMPAR, PCMPFR, and PCMPFR+NP are all soaked well in water (Figure S10 and Table S3), which has no negative effect when used as electrode materials in aqueous solution. Combining the results of CV, GCD, EIS, and long-term cycling, PCMPAR exhibited a favorable performance as supercapacitor electrode.

Electrochemical Tests in Two-Electrode System

The electrochemical performance of PCMPAR in a two-electrode system is shown in Figure S8. The PCMPAR showed similar rectangular CV curves as well as approximate triangular GCD profiles (Figures 7A and 7B), indicative of a primary EDLC performance. The specific capacitances of PCMPAR calculated by GCD profiles were 279, 255, 237, 210, 191, and 174 F g−1 at current densities of 0.5, 1, 2, 5, 10, and 20 A g−1, respectively (Figure 7C). These values were competitive during the carbon materials. Furthermore, the energy density and power density were calculated, and the results are shown in Figure 7D. PCMPAR exhibited an energy density of 9.7 Wh kg−1 or 6.0 Wh kg−1. This value corresponded to a power density of 0.25 kW kg−1 or 10 kW kg−1 in 6 M KOH electrolyte.

Figure 7.

Figure 7

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Electrochemical Characterization of the PCMPAR in Two-Electrode System

(A) CV curves of PCMPAR at different scan rates in a two-electrode system.

(B) GCD profiles of PCMPAR under different current densities.

(C) Specific capacitance of PCMPAR calculated by GCD profiles.

(D) Ragone plot of PCMPAR.

Discussion

Phosphoramide resin was synthesized, wherein the special N–P structure was chemically bonded as the nodes for linking the monomers into polymers. The N and P in the PAR framework can be transformed to NH4H2PO4 during carbonization. The well-distributed NH4H2PO4 acts as the in situ activating agent to form micro/mesopores, which has better effect on activation than post-added NH4H2PO4. The as-prepared PCMPAR has a high SSA of 2,620 m2 g−1 and pore volume of 1.49 cm3 g−1 and fine micro/mesoporous structure. Electrochemical tests show that PCMPAR has approximately rectangular CV curves and triangular GCD profiles. This finding indicates that PCMPAR is a typical EDLC electrode. The PCMPAR exhibits a specific capacitance of 440 F g−1 at 0.5 A g−1 and 278 F g−1 at 20 A g−1. The high capacitance retention at high charge-discharge rates signifies that PCMPAR has fine micro/mesoporous structure for the transport of electrolyte ions. The results show that PAR is a good candidate to prepare PCMs for supercapacitor because of its unique form of N and P in the framework.

Limitations of Study

Based on the current preparation method of PCMs from PAR involving drastic activation, it is hard to precisely control the pore size. Therefore we would design and synthesize more N, P resins by changing the monomers in future work and adopt the mild activation process. The effect of monomer structures on the characteristics of the PCMs should be investigated to optimize the design and preparation of new PCMs for energy storage, catalysis, environmental remediation, and so on.

Methods

All methods can be found in the accompanying Transparent Methods supplemental file.

Acknowledgments

The authors gratefully acknowledge financial support from National Natural Science Foundation of China (21677138) and the Key Special Program on the S&T for the Pollution Control and Treatment of Water Bodies (No. 2017ZX07603-003 and No.2012ZX07103−001).

Author Contributions

H.J. developed the concept, designed the experiment, analyzed the data, and composed the manuscript. B.-H.C carried out the experiments and wrote the article. R.J. Z. coordinated the project. All authors provided critical discussion of the data and ideas and gave input on the manuscript.

Declaration of Interests

The authors declare no competing interests.

Published: February 22, 2019

Footnotes

Supplemental Information includes Transparent Methods, 10 figures, 3 tables, and 2 data files and can be found with this article online at https://doi.org/10.1016/j.isci.2019.01.016.

Supplemental Information

Document S1. Transparent Methods, Figures S1–S10, and Tables S1–S3
mmc1.pdf (1.8MB, pdf)
Data S1. 3D-FTIR Spectra of PAR-Char + KOH, Related to Figure 5B

3D infrared spectrum of gaseous compounds released during pyrolysis of PAR-char + KOH.

mmc2.csv (6.8MB, csv)
Data S2. 3D-FTIR Spectra of PAR-Char, Related to Figure 5C

3D infrared spectrum of gaseous compounds released during pyrolysis of PAR-char.

mmc3.csv (9.6MB, csv)

References

  1. Böttger-Hiller F., Kempe P., Cox G., Panchenko A., Janssen N., Petzold A., Thurn-Albrecht T., Borchardt L., Rose M., Kaskel S. Twin polymerization at spherical hard templates: an approach to size-adjustable carbon hollow spheres with micro- or mesoporous shells. Angew. Chem. Int. Ed. 2013;52:6088–6091. doi: 10.1002/anie.201209849. [DOI] [PubMed] [Google Scholar]
  2. Chmiola J., Yushin G., Dash R., Gogotsi Y. Effect of pore size and surface area of carbide derived carbons on specific capacitance. J. Power Sources. 2006;158:765–772. [Google Scholar]
  3. Chmiola J., Yushin G., Gogotsi Y., Portet C., Simon P., Taberna P.L. Anomalous increase in carbon capacitance at pore sizes less than 1 nanometer. Science. 2006;313:1760–1763. doi: 10.1126/science.1132195. [DOI] [PubMed] [Google Scholar]
  4. Chuenchom L., Kraehnert R., Smarsly B.M. Recent progress in soft-templating of porous carbon materials. Soft Matter. 2012;8:10801–10812. [Google Scholar]
  5. Dutta S., Bhaumik A., Wu K.C.W. Hierarchically porous carbon derived from polymers and biomass: effect of interconnected pores on energy applications. Energy Environ. Sci. 2014;7:3574–3592. [Google Scholar]
  6. Estevez L., Dua R., Bhandari N., Ramanujapuram A., Wang P., Giannelis E.P. A facile approach for the synthesis of monolithic hierarchical porous carbons - high performance materials for amine based CO2 capture and supercapacitor electrode. Energy Environ. Sci. 2013;6:1785–1790. [Google Scholar]
  7. Guo C., Li N., Ji L., Li Y., Yang X., Lu Y., Tu Y. N- and O-doped carbonaceous nanotubes from polypyrrole for potential application in high-performance capacitance. J. Power Sources. 2014;247:660–666. [Google Scholar]
  8. Hasegawa G., Kanamori K., Kiyomura T., Kurata H., Abe T., Nakanishi K. Hierarchically porous carbon monoliths comprising ordered mesoporous nanorod assemblies for high-voltage aqueous supercapacitors. Chem. Mater. 2016;28:3944–3950. [Google Scholar]
  9. Hou J., Cao C., Idrees F., Ma X. Hierarchical porous nitrogen-doped carbon nanosheets derived from silk for ultrahigh-capacity battery anodes and supercapacitors. ACS Nano. 2015;9:2556–2564. doi: 10.1021/nn506394r. [DOI] [PubMed] [Google Scholar]
  10. Hu J., Wang H., Gao Q., Guo H. Porous carbons prepared by using metal–organic framework as the precursor for supercapacitors. Carbon. 2010;48:3599–3606. [Google Scholar]
  11. Hu M., Reboul J., Furukawa S., Torad N.L., Ji Q., Srinivasu P., Ariga K., Kitagawa S., Yamauchi Y. Direct carbonization of Al-based porous coordination polymer for synthesis of nanoporous carbon. J. Am. Chem. Soc. 2012;134:2864–2867. doi: 10.1021/ja208940u. [DOI] [PubMed] [Google Scholar]
  12. Huang Y.-B., Pachfule P., Sun J.-K., Xu Q. From covalent-organic frameworks to hierarchically porous B-doped carbons: a molten-salt approach. J. Mater. Chem. A. 2016;4:4273–4279. [Google Scholar]
  13. Kondrat S., Perez C.R., Presser V., Gogotsi Y., Kornyshev A.A. Effect of pore size and its dispersity on the energy storage in nanoporous supercapacitors. Energy Environ. Sci. 2012;5:6474–6479. [Google Scholar]
  14. Krüner B., Schreiber A., Tolosa A., Quade A., Badaczewski F., Pfaff T., Smarsly B.M., Presser V. Nitrogen-containing novolac-derived carbon beads as electrode material for supercapacitors. Carbon. 2018;132:220–231. [Google Scholar]
  15. Largeot C., Portet C., Chmiola J., Taberna P.-L., Gogotsi Y., Simon P. Relation between the ion size and pore size for an electric double-layer capacitor. J. Am. Chem. Soc. 2008;130:2730–2731. doi: 10.1021/ja7106178. [DOI] [PubMed] [Google Scholar]
  16. Li K., Li Y., Zheng Z. Kinetics and mechanism studies of p-nitroaniline adsorption on activated carbon fibers prepared from cotton stalk by NH4H2PO4 activation and subsequent gasification with steam. J. Hazard. Mater. 2010;178:553–559. doi: 10.1016/j.jhazmat.2010.01.120. [DOI] [PubMed] [Google Scholar]
  17. Li Y., Li Z., Shen P.K. Simultaneous formation of ultrahigh surface area and three-dimensional hierarchical porous graphene-like networks for fast and highly stable supercapacitors. Adv. Mater. 2013;25:2474–2480. doi: 10.1002/adma.201205332. [DOI] [PubMed] [Google Scholar]
  18. Li Z., Wu D., Liang Y., Fu R., Matyjaszewski K. Synthesis of well-defined microporous carbons by molecular-scale templating with polyhedral oligomeric silsesquioxane moieties. J. Am. Chem. Soc. 2014;136:4805–4808. doi: 10.1021/ja412192v. [DOI] [PubMed] [Google Scholar]
  19. Liang C., Dai S. Synthesis of mesoporous carbon materials via enhanced hydrogen-bonding interaction. J. Am. Chem. Soc. 2006;128:5316–5317. doi: 10.1021/ja060242k. [DOI] [PubMed] [Google Scholar]
  20. Liu T., Zhang F., Song Y., Li Y. Revitalizing carbon supercapacitor electrodes with hierarchical porous structures. J. Mater. Chem. A. 2017;5:17705–17733. [Google Scholar]
  21. Liu W., Zhang S., Dar S.U., Zhao Y., Akram R., Zhang X., Jin S., Wu Z., Wu D. Polyphosphazene-derived heteroatoms-doped carbon materials for supercapacitor electrodes. Carbon. 2018;129:420–427. [Google Scholar]
  22. Pandolfo A.G., Hollenkamp A.F. Carbon properties and their role in supercapacitors. J. Power Sources. 2006;157:11–27. [Google Scholar]
  23. Puthusseri D., Aravindan V., Madhavi S., Ogale S. 3D micro-porous conducting carbon beehive by single step polymer carbonization for high performance supercapacitors: the magic of in situ porogen formation. Energy Environ. Sci. 2014;7:728–735. [Google Scholar]
  24. Qie L., Chen W., Xu H., Xiong X., Jiang Y., Zou F., Hu X., Xin Y., Zhang Z., Huang Y. Synthesis of functionalized 3D hierarchical porous carbon for high-performance supercapacitors. Energy Environ. Sci. 2013;6:2497–2504. [Google Scholar]
  25. Salanne M., Rotenberg B., Naoi K., Kaneko K., Taberna P.L., Grey C.P., Dunn B., Simon P. Efficient storage mechanisms for building better supercapacitors. Nat. Energy. 2016;1:16070. [Google Scholar]
  26. Sevilla M., Fuertes A.B. Direct synthesis of highly porous interconnected carbon nanosheets and their application as high-performance supercapacitors. ACS Nano. 2014;8:5069–5078. doi: 10.1021/nn501124h. [DOI] [PubMed] [Google Scholar]
  27. Simon P., Gogotsi Y. Materials for electrochemical capacitors. Nat. Mater. 2008;7:845–854. doi: 10.1038/nmat2297. [DOI] [PubMed] [Google Scholar]
  28. Strauss V., Marsh K., Kowal M.D., El-Kady M., Kaner R.B. A simple route to porous graphene from carbon nanodots for supercapacitor applications. Adv. Mater. 2018;30:1704449. doi: 10.1002/adma.201704449. [DOI] [PubMed] [Google Scholar]
  29. Su Y.-Z., Xiao K., Li N., Liu Z.-Q., Qiao S.-Z. Amorphous Ni(OH)2 @ three-dimensional Ni core–shell nanostructures for high capacitance pseudocapacitors and asymmetric supercapacitors. J. Mater. Chem. A. 2014;2:13845–13853. [Google Scholar]
  30. Sun H., Wang J.-G., Zhang Y., Hua W., Li Y., Liu H. Ultrafast lithium energy storage enabled by interfacial construction of interlayer-expanded MoS2/N-doped carbon nanowires. J. Mater. Chem. A. 2018;6:13419–13427. [Google Scholar]
  31. Tang C., Liu Y., Yang D., Yang M., Li H. Oxygen and nitrogen co-doped porous carbons with finely-layered schistose structure for high-rate-performance supercapacitors. Carbon. 2017;122:538–546. [Google Scholar]
  32. Tao Y., Kanoh H., Abrams L., Kaneko K. Mesopore-modified zeolites:  preparation, characterization, and applications. Chem. Rev. 2006;106:896–910. doi: 10.1021/cr040204o. [DOI] [PubMed] [Google Scholar]
  33. Tian W., Gao Q., Tan Y., Yang K., Zhu L., Yang C., Zhang H. Bio-inspired beehive-like hierarchical nanoporous carbon derived from bamboo-based industrial by-product as a high performance supercapacitor electrode material. J. Mater. Chem. A. 2015;3:5656–5664. [Google Scholar]
  34. Tran C., Kalra V. Fabrication of porous carbon nanofibers with adjustable pore sizes as electrodes for supercapacitors. J. Power Sources. 2013;235:289–296. [Google Scholar]
  35. Wang G., Zhang L., Zhang J. A review of electrode materials for electrochemical supercapacitors. Chem. Soc. Rev. 2012;41:797–828. doi: 10.1039/c1cs15060j. [DOI] [PubMed] [Google Scholar]
  36. Wang J.-G., Kang F., Wei B. Engineering of MnO2-based nanocomposites for high-performance supercapacitors. Prog. Mater. Sci. 2015;74:51–124. [Google Scholar]
  37. Wang J.-G., Liu H., Liu H., Hua W., Shao M. Interfacial constructing flexible V2O5@polypyrrole core–shell nanowire membrane with superior supercapacitive performance. ACS Appl. Mater. Interfaces. 2018;10:18816–18823. doi: 10.1021/acsami.8b05660. [DOI] [PubMed] [Google Scholar]
  38. Wang J.-G., Liu H., Sun H., Hua W., Wang H., Liu X., Wei B. One-pot synthesis of nitrogen-doped ordered mesoporous carbon spheres for high-rate and long-cycle life supercapacitors. Carbon. 2018;127:85–92. [Google Scholar]
  39. Wang J.-G., Sun H., Liu H., Jin D., Liu X., Li X., Kang F. Triaxialnanocables of conducting polypyrrole@SnS2@carbon nanofiber enabling significantly enhanced Li-Ion storage. ACS Appl. Mater. Interfaces. 2018;10:13581–13587. doi: 10.1021/acsami.8b02111. [DOI] [PubMed] [Google Scholar]
  40. Wang J., Kaskel S. KOH activation of carbon-based materials for energy storage. J. Mater. Chem. 2012;22:23710–23725. [Google Scholar]
  41. Wei J., Zhou D., Sun Z., Deng Y., Xia Y., Zhao D. A controllable synthesis of rich nitrogen-doped ordered mesoporous carbon for CO2 capture and supercapacitors. Adv. Funct. Mater. 2013;23:2322–2328. [Google Scholar]
  42. Xiong S., Fan J., Wang Y., Zhu J., Yu J., Hu Z. A facile template approach to nitrogen-doped hierarchical porous carbon nanospheres from polydopamine for high-performance supercapacitors. J. Mater. Chem. A. 2017;5:18242–18252. [Google Scholar]
  43. Xu B., Zheng D., Jia M., Cao G., Yang Y. Nitrogen-doped porous carbon simply prepared by pyrolyzing a nitrogen-containing organic salt for supercapacitors. Electrochim. Acta. 2013;98:176–182. [Google Scholar]
  44. Xu D., Tong Y., Yan T., Shi L., Zhang D. N,P-codopedmeso-/microporous carbon derived from biomass materials via a dual-activation strategy as high-performance electrodes for deionization capacitors. ACS Sustain. Chem. Eng. 2017;5:5810–5819. [Google Scholar]
  45. Yao L., Wu Q., Zhang P., Zhang J., Wang D., Li Y., Ren X., Mi H., Deng L., Zheng Z. Scalable 2D hierarchical porous carbon nanosheets for flexible supercapacitors with ultrahigh energy density. Adv. Mater. 2018;30:1706054. doi: 10.1002/adma.201706054. [DOI] [PubMed] [Google Scholar]
  46. Yu D., Goh K., Wang H., Wei L., Jiang W., Zhang Q., Dai L., Chen Y. Scalable synthesis of hierarchically structured carbon nanotube–graphene fibres for capacitive energy storage. Nat. Nanotechnol. 2014;9:555. doi: 10.1038/nnano.2014.93. [DOI] [PubMed] [Google Scholar]
  47. Zeng F.-X., Liu W.-J., Luo S.-W., Jiang H., Yu H.-Q., Guo Q.-X. Design, preparation, and characterization of a novel hyper-cross-linked polyphosphamide polymer and its adsorption for phenol. Ind. Eng. Chem. Res. 2011;50:11614–11619. [Google Scholar]
  48. Zhai Y., Dou Y., Zhao D., Fulvio P.F., Mayes R.T., Dai S. Carbon materials for chemical capacitive energy storage. Adv. Mater. 2011;23:4828–4850. doi: 10.1002/adma.201100984. [DOI] [PubMed] [Google Scholar]
  49. Zhang L., Jiang Y., Wang L., Zhang C., Liu S. Hierarchical porous carbon nanofibers as binder-free electrode for high-performance supercapacitor. Electrochim. Acta. 2016;196:189–196. [Google Scholar]
  50. Zhang L.L., Zhao X.S. Carbon-based materials as supercapacitor electrodes. Chem. Soc. Rev. 2009;38:2520–2531. doi: 10.1039/b813846j. [DOI] [PubMed] [Google Scholar]
  51. Zhang P., Yuan J., Fellinger T.-P., Antonietti M., Li H., Wang Y. Improving hydrothermal carbonization by using poly(ionic liquid)s. Angew. Chem. Int. Ed. 2013;52:6028–6032. doi: 10.1002/anie.201301069. [DOI] [PubMed] [Google Scholar]
  52. Zheng C., Qi L., Yoshio M., Wang H. Cooperation of micro- and meso-porous carbon electrode materials in electric double-layer capacitors. J. Power Sources. 2010;195:4406–4409. [Google Scholar]
  53. Zheng X., Luo J., Lv W., Wang D.-W., Yang Q.-H. Two-dimensional porous carbon: synthesis and ion-transport properties. Adv. Mater. 2015;27:5388–5395. doi: 10.1002/adma.201501452. [DOI] [PubMed] [Google Scholar]
  54. Zhong M., Kim E.K., McGann J.P., Chun S.-E., Whitacre J.F., Jaroniec M., Matyjaszewski K., Kowalewski T. Electrochemically active nitrogen-enriched nanocarbons with well-defined morphology synthesized by pyrolysis of self-assembled block copolymer. J. Am. Chem. Soc. 2012;134:14846–14857. doi: 10.1021/ja304352n. [DOI] [PubMed] [Google Scholar]
  55. Zhou J., Zhu T., Xing W., Li Z., Shen H., Zhuo S. Activated polyaniline-based carbon nanoparticles for high performance supercapacitors. Electrochim. Acta. 2015;160:152–159. [Google Scholar]
  56. Zhu D., Wang Y., Gan L., Liu M., Cheng K., Zhao Y., Deng X., Sun D. Nitrogen-containing carbon microspheres for supercapacitor electrodes. Electrochim. Acta. 2015;158:166–174. [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Document S1. Transparent Methods, Figures S1–S10, and Tables S1–S3
mmc1.pdf (1.8MB, pdf)
Data S1. 3D-FTIR Spectra of PAR-Char + KOH, Related to Figure 5B

3D infrared spectrum of gaseous compounds released during pyrolysis of PAR-char + KOH.

mmc2.csv (6.8MB, csv)
Data S2. 3D-FTIR Spectra of PAR-Char, Related to Figure 5C

3D infrared spectrum of gaseous compounds released during pyrolysis of PAR-char.

mmc3.csv (9.6MB, csv)

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