An Efficient Design for High-Energy and High-Power Capability Hybrid

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An Efficient Design for High-Energy and High-Power Capability Hybrid Electric Power Device with Enhanced Electrochemical Interfaces Ruili Sun, Zhangxun Xia, Fulai Qi, Fenning Jing, Ruoyi Deng, Suli Wang, and Gongquan Sun ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b01863 • Publication Date (Web): 10 May 2019 Downloaded from http://pubs.acs.org on May 10, 2019

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An Efficient Design for High-Energy and HighPower Capability Hybrid Electric Power Device with Enhanced Electrochemical Interfaces Ruili Sun1, 2, Zhangxun Xia1, Fulai Qi 3, Fenning Jing1, Ruoyi Deng1, 2, Suli Wang1,*, Gongquan Sun1,* 1 Division of Fuel Cell & Battery, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China 2 University of Chinese Academy of Sciences, Beijing 100049, China 3 Institutes of Metal Research, Chinese Academy of Science, Shenyang 110016, China KEYWORDS：Hybrid Electrode, Electrochemical Interfaces, Hybrid Electric Power Device ABSTRACT: Fabrication of novel electrode architectures with tailored electrochemical interfaces is an effective strategy for enhancing charge and mass transport processes within electrochemical devices. Here, we design and fabricate a well-hybrid electrode based on the coupling of polyaniline (PANI) nanowires and Pt-based electrocatalysts to manufacture a hybrid electric power device (HEPD) combining with advantages of supercapacitors and fuel cells. Due to the boosted charge transfer between PANI nanowires and Pt-based materials via enhanced electrochemical interfaces, the HEPD assembled with hybrid electrodes shows remarkable performance with a peak power density of 222 mW cm-2, a specific power of 3810 W kg-1 and a


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specific energy of 2100 Wh kg-1, normalized to the mass of membrane electrode assemblies (MEAs). The in-situ Raman spectra and extended electrochemical studies demonstrate the intrinsic mechanism of charge transfer processes within hybrid electrodes, shedding lights for the alternative progress of electrochemical energy conversion systems and storage devices. Introduction With the rapid progress of electrochemical energy conversion systems and storage devices for these decades, energy devices with high specific energy and high specific power have been indeed demanded.1-4 As one of the most prospective alternative energy conversion devices, direct methanol fuel cells (DMFCs) have attracted much attention duo to their relatively high specific energy, easy transport and low pollutant emissions.5,6 However, because of the sluggish kinetics for electrochemical catalysis of oxygen reduction and methanol oxidation, the bad power output remains one of the major challenges for the large-scale commercialization of DMFCs.7 Although great achievements have been gained to enhance the activity and utilization of electrocatalysts for electrochemical reactions by designing high-activity Pt-based electrocatalysts8-12 or constructing novel electrode structures,13,14 DMFCs still suffer from the low power performance challenge (< 160 W cm-2, the target of DOE). Due to their ultrafast charge transport nature, supercapacitors have been regarded as ultra-high specific power (> 1000 W kg-1) electrochemical devices in comparison with secondary batteries or fuel cells.15 Therefore, a coupling system of supercapacitors and fuel cells, or called hybrid electric power devices (HEPD) should be an effective strategy for developing a novel electrochemical energy conversion system with high specific power and high specific energy.16-18 HEPD, where electric energy could be conversed and stored at the same time, are primarily constructed through linking different parts by the power equipment.19 Such complex electronic interfaces for the fuel cell, the capacitor or power management equipment, could bring in the challenge in the construction and performance for hybrid energy devices, and decrease the


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specific power and specific energy of HEPD. Based on abovementioned challenges, Shleev et al. created a new kind of hybrid electric power biodevice by combining biofuel cells and supercapacitors into a single system, which achieved a specific power and specific energy of 23 W kg-1 and 0.5 Wh kg-1.18 The hybrid at the electrode level could be considered as a practical method to obtain the electric power system with high specific power and high specific energy. Nevertheless, the poor performance of biofuel cells obstructs the development of hybrid biodevices in electrochemical energy conversion systems and storage devices.16 Hence, substituting biofuel cells with other types of energy devices may improve the performance of HEPD.19-21 Recently, some researchers have introduced secondary batteries to fabricate hybrid electric power devices, such as rechargeable batteries or accumulators.21 However, few investigations have been conducted on DMFC-based hybrid devices. According to abovementioned design strategies, our group employed the polyaniline (PANI) conductive polymer to fabricate a novel HEPD with the advantages of DMFCs and supercapacitors via hybrid electrodes, viz. a discrete electrode concurrently behaving electrocatalytic and charge-storage feature.22 Because of the unique synergy of electrochemical reactions and pseudo-capacitive processes, dual-function electrodes could achieve a specific energy of 1550 Wh kg-1 and a specific power of 4080 W kg-1. However, limited electrochemical interfaces constructed by pseudo-capacitor materials and electrochemical catalysts could affect the power density of abovementioned electrodes. Meanwhile complex fabrication processes of these electrodes could be the potential drawback for their further application in electrochemical energy devices. Additionally, the intrinsic mechanism for hybrid electrodes of HEPD has rarely been reported to the best of our knowledge, which have been recognized as the significant factor for the construction of HEPD at the electrode level. In this study, we propose a novel hybrid electrode with the coupling of ultrafast charge transport processes and electrochemical reactions based on extended electrochemical interfaces


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between polyaniline (PANI) nanowires and Pt-based electrocatalysts to obtain the ultrahigh transient power output. By optimizing electrode structures and electrode fabrication conditions, structural parameters of the hybrid electrode are adjusted to fulfill requirements of the ideal electrode fabricated with PANI materials and electrocatalysts. The charge transport and storage mechanism within this hybrid electrode between electrochemical reactions (oxygen reduction reaction and methanol oxidation reaction) and transition processes of different oxidation states of PANI is also discussed. Results and Discussion The construction of this hybrid electrode is displayed in Scheme 1. In this manuscript, we used the carbon cloth as the gas diffusion layer (GDL) to form the following hybrid electrode. Clearly, different preparation methods could significantly alter electrochemical interfaces between supercapacitor materials and electrocatalysts for hybrid electrodes. Pt/C-PANI-GDL-EI electrode was fabricated via the uniform mixture of PANI capacitor materials, ionomer materials and electrocatalysts to form extended electrochemical interfaces (EI) for electrocatalysts and supercapacitor materials. Additionally, spraying the catalyst ink containing electrocatalysts and ionomer materials on the carbon cloth modified by PANI capacitor materials (PANI-GDL) could fabricate the independent PANI layer and catalytic layer to form the hybrid electrode with layered electrochemical interfaces (LS), denoted as Pt/C-PANI-GDL-LS electrode.


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Scheme 1. Schematics of the fabrication process for Pt/C-PANI-GDL-EI (a) and Pt/C-PANIGDL-LS (b).

Morphological details of hybrid electrodes are demonstrated in Figure 1. Normally, these electrocatalysts sprayed onto the PANI-GDL displayed as the thin film structure around carbonnanowires modified by PANI nanoarrays (Figure S2 and S3), and the distribution of the nitrogen element in the EDS image indicated that PANI nanoarrays was demonstrated as the uniform distribution in the carbonfiber of the carbon cloth of the Pt/C-PANI-GDL-LS electrode. From the top view mapping figures, it was obvious that many electrocatalysts located on the carbon cloth and could not construct electrochemical interfaces with PANI materials, resulting in the insufficient contact for PANI materials and electrocatalysts. Nevertheless, via introducing PANI materials into the catalytic layer, Pt/C-PANI-GDL-EI electrodes exhibited a more sufficient contact for PANI and electrocatalysts from results of the figure 1d and S1a. Additionally, the uniform distribution of the nitrogen element for the Pt/C-PANI-GDL-EI electrode implied that PANI nanowires23 with the average diameter of 40-70 nm, evenly distributed in the catalytic layer of hybrid electrodes. This result demonstrated that Pt/C-PANI-GDL-EI electrodes should have an extended electrochemical interface and might obtain a higher capability of transporting


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and storing charge. Hence, the discrepancy in electrochemical interfaces for these electrodes might bring out the difference in the performance of HEPD.

Figure 1. SEM images of Pt/C-PANI-GDL-EI (a, d), Pt/C-PANI-GDL-LS (b, e) and Pt/CGDL (c, f); mapping images of Pt/C-PANI-GDL-EI (g), Pt/C-PANI-GDL-LS (h) and Pt/C-GDL (i). Synergistic effects of the charge transfer between pseudocapacitor materials and electrocatalysts can be demonstrated as the potential coupling of different electrochemical processes. In brief, the fast kinetics of the transition processes for different oxidation states of PANI could be applied to the high charge/discharge rates of electrocatalysts of DMFCs because the potential of pseudo-capacitive processes of PANI materials matches with the potential of DMFCs. Namely, in the open circuit, at a cathode side, the charge and proton are transferred to oxygen and then the oxygen reduction reaction (ORR) occurs where PANI was found to change


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to the Pernigraniline. And PANI could be reduced from the Emeraldine to Leucoemeraldine at an anode side, because of the charge and proton from the methanol oxidation reaction (MOR). In addition, the PANI of hybrid electrodes might suffer opposite redox reactions during the discharge process. Hence, pseudo-capacitive processes of PANI might be benefit for electrochemical reactions of DMFCs. Furthermore, in-situ electrochemical Raman spectroscopy on the PtRu-GDL, PtRu-PANI-GDL-LS and PtRu-PANI-GDL-EI electrodes was carried out to demonstrate synergistic effects of the charge transfer between pseudocapacitor materials and electrocatalysts, as shown in Fig. 2. At the beginning, a series of PANI Raman spectra were achieved via varying the operating potential from 0.04-0.84 V vs. RHE in the Raman measuring equipment (Fig. S4).24 It was worth noting that when the potential was applied to the PANIGDL, the spectral peaks of 1160 cm-1 and 1186 cm-1 caused by C-H bending vibrations of PANI were observed to disperse or raise, indicating that PANI was found to change between an Emeraldine form and a Leucoemeraldine form. Therefore, these peaks of PANI could be employed to demonstrate whether there existed the charge transfer between pseudocapacitor materials and electrocatalysts. According to above results, a two-electrode electrochemical cell was carried out to analyze the interaction between PANI materials and electrocatalysts of hybrid electrodes (Fig. S4). Apparently, the original PANI from the side of PANI-GDL electrode was found as the mixture of the Emeraldine form and Leucoemeraldine form (Fig. S5), and then PANI was found to change to the Leucoemeraldine form when the methanol was put in the side of PtRu-GDL (in Fig. 2, denoted as PtRu-GDL). These phenomena showed that during the methanol oxidation reaction, charges and protons from MOR were transmitted to another side of PtRu-GDL via the external wire and caused the PANI of another side electrode to be transformed from the Emeraldine to Leucoemeraldine. Moreover, when the same operation was carried out


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on the side of PtRu-PANI-GDL-LS, the PANI of another side electrode partially remained in the original form (in the Fig. 2, denoted as PtRu-PANI-GDL-LS), implied that electrons and protons generated by MOR at the PtRu-PANI-GDL-LS electrodes could not be entirely transferred to the PANI of another side. However, for PtRu-PANI-GDL-EI electrodes, the PANI of PANI-GDL electrode remained the original form even if the methanol was put in the side of PtRu-PANIGDL-EI (in Fig. 2, denoted as PtRu-PANI-GDL-EI). It was obvious that charges and protons from MOR should be transmitted to the PANI of PtRu-PANI-GDL-EI electrode, and could not bring out the reduction of PANI on another side. Hence, these results exhibited electrons and protons generated by electrochemical reactions indeed transferred through electrochemical interfaces between PANI materials and electrocatalysts of hybrid electrodes. Therefore, electrochemical interfaces from pseudocapacitor materials and electrocatalysts have a significant influence on charge transfer processes, and then affect the performance of the HEPD.

Figure 2. (a) Raman spectra of PANI at different potentials and different electrodes；(b) Electrode charge-discharge processes for hybrid electrodes. To evaluate the electrochemical catalytic performance of Pt/C-PANI-GDL-EI, a series of measurements were conducted in a three-electrode electrochemical system. Attributed to the relationship between electrochemical redox reactions of electrocatalysts and pseudo capacitance processes of PANI materials, Pt/C-PANI-GDL-EI displayed significantly discrepancy in the CV curve in comparison with that of Pt/C-PANI-GDL-LS and Pt/C-GDL, as illustrated in Fig. S6.


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Although the electrochemical surface area (ECSA) of different electrodes was similar (Table S1), the galvanostatic discharge and stability curves exhibited noticeable discrepancy in the ORR activity for these electrodes. As shown in Fig. S7, the open circuit potential (OCV) of galvanostatic discharge curves of Pt/C-PANI-GDL-EI could have a large positive shift in comparison with that of Pt/C-PANI-GDL-LS, but was similar to that of Pt/C-GDL. Additionally, Pt/C-PANI-GDL-EI showed greater capacitance than Pt/C-PANI-GDL-LS, as seen by extending the discharge time to reach the selected potential. Moreover, Pt/C-PANI-GDL-EI also revealed a small potential decay-rate after the 3-hour galvanostatic discharge test. This suggests that unique electrochemical interfaces of Pt/C-PANI-GDL-EI facilitate the supply of the pseudo-capacitance of PANI and the electrochemical activity of electrocatalysts. CV and galvanostatic discharge curves of PtRu-PANI-GDL-EI were also tested as shown in Figure S8 and S9. From the CV curves, a larger double-layer was observed in the PtRu-PANIGDL-EI curve compared to PtRu-PANI-GDL-LS and PtRu-GDL, which was connected with the transformation of different PANI forms. Meanwhile, in galvanostatic discharge performance curves, PtRu-PANI-GDL-EI displayed an OCV similar to that of PtRu-GDL at the beginning of 100 s, implying that the novel electrode structure of PtRu-PANI-GDL-EI should not influence the activity of electrocatalyst. The discharge curve of PtRu-PANI-GDL-EI was then divided into three parts, in which the pseudo capacitance provided by PANI materials was observed by prolonging the discharge time to reach a selected potential, which was similar to PtRu-PANIGDL-LS. This means that the novel electrode structure of PtRu-PANI-GDL-EI should be benefit to the pseudo capacitance of PANI. In addition, PtRu-PANI-GDL-EI showed less potential decay-rate after the 3-hour galvanostatic discharge test over PtRu-GDL. With the above phenomena, unique electrochemical interfaces of PtRu-PANI-GDL-EI electrode could have


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obvious benefit for the pseudo capacitance of PANI and the electrochemical activity, which is consistent in the results of Pt/C-PANI-GDL-EI.

Figure 3. Stability curves of HEPD-EI under different discharge conditions. The red plot obtained with 0.5 M CH3OH and air under 100 mAcm-2; the pink plot achieved with H2O and air under 2 Ω; the dark plot obtained with 0.5 M CH3OH and N2 under 2 Ω; the blue plot achieved with H2O and t N2 under 2 Ω; The temperature was 80 °C, the anode flow rate was 1.0 ml min-1 and the cathode was 80 sccm. To further study the performance for the applied situation of DMFCs, Pt/C-PANI-GDL-EI and PtRu-PANI-GDL-EI were assembled as the cathode and anode of HEPD-EI, and then measured, and results were demonstrated in Fig. 3 and S11. Duo to the improvement in the pseudo capacitance of PANI, the single cell equipped with these hybrid electrodes (HEPD) also remarkably outperformed in the stability measurement, in which the anode side was 0.5 M CH3OH and the cathode side was air. Stability curves were remarkably different from curves obtained under other test conditions (such as supplying the cathode fed with air and anode with H2O). It indicates that electrons and protons generated by MOR and ORR could be transferred between PANI pseudo-capacitor materials and electrocatalysts during electrochemical processes, which plays the vital role in the providence of the pseudo-capacitance of PANI and electrochemically catalytic reactions for HEPD-EI.


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IV curves were applied to investigate the influence of different electrochemical interfaces on the performance of HEPD. As illustrated in Fig. 4, a single cell equipped with Pt/C-PANI-GDLEI and PtRu-PANI-GDL-EI (HEPD-EI-0.2) displayed the similar performance in comparison with that of DMFC and HEPD-LS. The peak power density of HEPD-EI-0.2 was 97 mW cm-2 while DMFC and HEPD-LS were 114 m Wcm-2 and 111 mW cm-2. Because of the discrepancy in the voltage of high current density (>200 mA cm-2) and the catalyst loading of fuel cells, the peak power density showed the sight difference. However, due to the outstanding synergistic effects of the charge transfer between charge-discharge processes and electrochemical reactions of these hybrid electrodes, the HEPD-EI-0.2 with about 0.6 mg cm-2 of PANI mass loading highlighted the significantly enhancement in the specific power of the intermittent pulse discharge test, in comparison with that of HEPD-LS with about 1.7 mg cm-2 of PANI mass loading. Additionally, the HEPD-EI-0.2 with the intermittent peak power density of 205 mW cm2

exhibited a 1.11-fold enhancement compared to the steady performance, which outperformed

the 0.42-fold and 0.91-fold enhancement for DMFC and HEPD-LS. Moreover, the stability test was conducted via the discharge pulse procedure of Figure S10 and curves were displayed in Fig. 4f. Clearly, the voltage for DMFC, HEPD-LS and HEPD-EI-0.2 declined by 12.9 mW h-1, 10.1 mW h-1 and 7.9 mW h-1, indicating the outstanding stability for HEPD-EI-0.2 single cell at the pulse discharge test.


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Figure 4. Polarization curves of different HEPD and DMFC for the steady measurement (a) and the intermittent pulse discharge (c). (b) Voltage drops by applied discharge pulses with different current densities. (d) Comparison of the power density for DMFC and HEPD. (e) EIS curves at 100 mA cm-2. (f) Stability curves at 100 mA cm-2. Contact structured interfaces denoted as (CS) Table 1. EIS fitting parameters for different HEPD and DMFC RΩ(mΩ)

Rcct(mΩ)

CPEcct-P

CPEcct-T(F)

Ract(mΩ)

CPEact-P

CPEact-T(F)

DMFC

30.0

30.0

0.65

0.098

19.0

0.76

0.049

HEPD-CS

32.5

28.0

0.62

0.295

19.4

0.71

0.14

HEPD-LS

24.0

28.0

0.66

0.280

18.6

0.76

0.13

HEPD-EI-0.2

20.0

22.0

0.68

0.340

17.0

0.82

0.13

The enhancement in the electrochemical performance should be further proofed by electrochemical impedance spectra (EIS) results, as illustrated in Fig. 4e and S12. Based on electrochemical equivalent circuit results, EIS fitting parameters for different HEPD and DMFC were set out in the table 1.25 Obviously, the charge transfer resistance of HEPD-EI-0.2 at cathode and anode (22.0 mΩ and 17.0 mΩ) were smaller than those of HEPD-LS (28.0 mΩ and 18.6 mΩ), which evidenced the fast kinetic of charge processes between electrochemical reactions


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and charge-discharge processes for HEPD. Meanwhile, the capacitance of HEPD-EI-0.2 with about 0.6 mg cm-2 of PANI mass loading for anode and cathode sides (0.130 F and 0.340) were larger than those of HEPD-LS (0.280 and 0.130 F) with about 1.7 mg cm-2 of PANI mass loading and DMFC (0.098 and 0.049 F) in accord with the results of above electrodes electrochemical measurements. Hence, the fast charge transfer between charge-discharge processes and electrochemical reactions for Pt/C-PANI-GDL-EI and PtRu-PANI-GDL-EI are the important factor of the high specific power and excellent stability performance for HEPD-EI-0.2.

Figure 5. The polarization curves of different HEPD-EI at the steady measurement (a) and the intermittent pulse discharge (b). Comparison of the power density for different HEPD-EI single cells (c). The intermittent discharge curves at different current densities (d). Stability curves under 100 mA cm-2 (e). EIS curves under 100 mA cm-2 (f). Many hybrid electrodes (such as Pt/C-PANI-GDL-EI with different mass ratio of PANI and electrocatalysts) with different electrochemical interfaces were equipped and tested to further certify the abovementioned conclusion, as shown in Figure 5. From the figure, the steady and intermittent peak power density firstly presented the increasing trend when the mass ratio of PANI and electrocatalysts increased from 1:0.1 to 1:0.4, and then both performances decreased with the increasing of the mass ratio of PANI and electrocatalysts. Even though these HEPD-EI


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were tested at the intermittent discharge of different current density (0, 10, 50, 100 and 200 mA cm-2), there still existed the similar tendency. Additionally, after the stability test conducted for 10800 s, the HEPD-EI exhibited the similar voltage declined rate, implying the outstanding stability of HEPD-EI electrodes. Based on the difference in the contact degree for PANI and electrocatalysts of these electrodes, the discrepancy for the performance of HEPD-EI could be related to the electrochemical interfaces between PANI and electrocatalysts. Hence, HEPD-EI single cells could demonstrate the excellent performance via constructing the novel structure with the superior electrochemical interfaces between pseudocapacitor materials and electrocatalysts. Conclusions Here in this work, based on the potential coupling of polyaniline (PANI) nanowires and Pt-based electrocatalysts, we design and fabricate an enhanced hybrid electrode with extended electrochemical interfaces for constructing a hybrid electrochemical power device. In-situ Raman spectra and extended electrochemical studies have demonstrated that electrons and protons indeed transfer between the catalytic active sites and the pseudo-capacitor through electrochemical interfaces during the electrochemical reactions of DMFCs. The significant synergy of electrochemical reactions and pseudo capacitive processes creates the high power density of 222 mW cm-2, the specific power of 3810 W kg-1 and the specific energy of 2100 Wh kg-1 for HEPD in the electrode level. Such electrode structure could exhibit great potentials in the application including electric vehicles and energy devices. Moreover, the development for HEPD might bring in lights for the future of energy conversion systems and storage devices. ASSOCIATED CONTENT


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Supporting Information Experimental Section; preparation processes, physical characterizations and electrochemical measurements of DMFC and HEPD; electrochemical surface area for different electrodes (Table S1); capacitance properties for different electrodes (Table S2); single cell parameters for DMFC and HEPD (Table S3); single cell performance for DMFC and HEPD (Table S4); the calculation processes of specific energy and specific power density of HEPD; EDS images for Hybrid electrodes (Figure S1); SEM images of the pure carbon cloth and PANI-GDL (Figure S2); Mapping figures of PtRu-PANI-GDL-LS electrode (Figure S3); schematic of Raman spectra measurement (Figure S4); XPS spectra of the N 1s peak of PANI-GDL (Figure S5); CV curves, galvanostatic discharge curves and stability curves for hybrid electrodes (Figure S6, S7, S8 and S9); experimental setup of discharge pulse (Figure S10); charge-discharge curve of HEPD-EI (Figure S11); electrochemical equivalent circuit (Figure S12) and polarization curves of different single cells (Figure S13). The following files are available free of charge. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]; [email protected] ORCID: Gongquan Sun: 0000-0001-8414-8894 Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Funding Sources


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The work is financially supported by “Transformational Technologies for Clean Energy and Demonstration”, Strategic Priority Research Program of the Chinese Academy of Science, Grant No. XDA21090203 and the “High temperature methanol fuel cell electric vehicle power supply system”, the Program of the Chinese Academy of Science, Grant No. KFZD-SW-419. REFERENCES (1) Kongkanand, A.; Mathias, M. F. The Priority and Challenge of High-Power Performance of Low-Platinum Proton-Exchange Membrane Fuel Cells. J. Phys. Chem. Lett. 2016, 7, 1127-1137. (2) Lin, C. F.; Qi, Y.; Gregorczyk, K.; Lee, S. B.; Rubloff, G. W. Nanoscale Protection Layers to Mitigate Degradation in High-Energy Electrochemical Energy Storage Systems, Acc. Chem. Res. 2018, 51, 97-106. (3) Banham, D.; Ye, S. Current Status and Future Development of Catalyst Materials and Catalyst Layers for Proton Exchange Membrane Fuel Cells: An Industrial Perspective, ACS Energy Lett. 2017, 2, 629-638. (4) Wei, Q.; Xiong, F.; Tan, S.; Huang, L.; Lan, E. H.; Dunn, B.; Mai, L. Porous One-Dimensional Nanomaterials: Design, Fabrication and Applications in Electrochemical Energy Storage, Adv. Mater. 2017, 29, NO. 1602300. (5) Tang, H.; Wang, S.; Pan, M.; Jiang, S. P.; Ruan, Y. Performance of Direct Methanol Fuel Cells Prepared by Hot-pressed MEA and Catalyst-coated Membrane (CCM), Electrochim. Acta 2007, 52, 3714-3718. (6) Liu, G.; Li, X.; Wang, M.; Wang, M.; Kim, J. Y.; Woo, J. Y.; Wang, X.; Lee, J. K. A Study on Anode Diffusion Layer for Performance Enhancement of A Direct Methanol Fuel Cell, Energy Convers. Manage. 2016, 126, 697-703. (7) Tiwari, J. N.; Tiwari, R. N.; Singh, G.; Kim, K. S. Recent Progress in the Development of Anode and Cathode Catalysts for Direct Methanol Fuel Cells, Nano Energy 2013, 2, 553-578. (8) Wang, C.; Zheng, L.; Chang, R.; Du, L.; Zhu, C.; Geng, D.; Yang, D. PalladiumCobalt Nanowires Decorated with Jagged Appearance for Efficient Methanol Electro-oxidation, ACS Appl. Mater. Inter. 2018, 10, 29965-29971. (9) Yang, Z.; Kim, C.; Hirata, S.; Fujigaya, T.; Nakashima, N. Facile Enhancement in CO-Tolerance of a Polymer-Coated Pt Electrocatalyst Supported on Carbon Black: Comparison between Vulcan and Ketjenblack , ACS Appl. Mater. Inter. 2015, 7, 15885-15891. (10) Melvin, A. A.; Joshi, V. S.; Poudyal, D. C.; Khushalani, D.; Haram, S. K. Electrocatalyst on Insulating Support?: Hollow Silica Spheres Loaded with Pt Nanoparticles for Methanol Oxidation , ACS Appl. Mater. Inter. 2015, 7, 6590-6595. (11) Kwon, S.; Ham, D. J.; Kim, T.; Kwon, Y.; Lee, S. G.; Cho, M. Active Methanol Oxidation Reaction by Enhanced CO Tolerance on Bimetallic Pt/Ir Electrocatalysts Using Electronic and Bifunctional Effects , ACS Appl. Mater. Inter. 2018, 10, 39581-39589. (12) Liu, Z.; Su, F.; Zhang, X.; Tay, S. W. Preparation and Characterization of PtRu Nanoparticles Supported on Nitrogen-Doped Porous Carbon for Electrooxidation of Methanol, ACS Appl. Mater. Inter. 2011, 3, 3824-3830.


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(13) Xia, Z.; Wang, S.; Li, Y.; Jiang, L.; Sun, H.; Zhu, S.; Su, D. S.; Sun, G. Vertically Oriented Polypyrrolenanowire Arrays on Pd-plated Nafion® Membrane and its Application in Direct Methanol fuel Cells , J. Mater. Chem. A 2013, 1, 491-494. (14) Xia, Z.; Wang, S.; Jiang, L.; Sun, H.; Sun, G. Controllable Synthesis of Vertically Aligned Polypyrrole Nanowires as Advanced Electrode Support for Fuel Cells, J. Power Sources 2014, 256, 125-132. (15) Jiang, H.; Lee, P. S.; Li, C. 3D Carbon Based Nanostructures for Advanced Supercapacitors, Energy Environ. Sci. 2013, 6, 41-53. (16) Pankratov, D.; Blum, Z.; Shleev, S. Hybrid Electric Power Biodevices, ChemElectroChem 2014, 1, 1798-1807. (17) Pankratov, D.; Blum, Z.; Suyatin, D. B.; Popov, V. O.; Shleev, S. Hybrid Electric Power Biodevices, ChemElectroChem 2014, 1, 343-346. (18) Pankratov, D.; Falkman, P.; Blum, Z.; Shleev, S. A Hybrid Electric Power Device for Simultaneous Generation and Storage of Electric Energy, Energy Environ. Sci. 2014, 7, 989993. (19) Carignano, M. G.; Costa-Castelló, R.; Roda, V.; Nigro, N. M.; Junco, S.; Feroldi, D. Energy Management Strategy for Fuel Cell-Supercapacitor Hybrid Vehicles Based on Prediction of Energy Demand, J. Power Sources 2017, 360, 419-433. (20) Aouzellag, H.; Ghedamsi, K.; Aouzellag, D. Energy Management and Fault Tolerant Control Strategies for Fuel Cell/Ultra-Capacitor Hybrid Electric Vehicles to Enhance Autonomy, Efficiency and Life Time of The Fuel cell system, Int. J. Hydrogen Energy 2015, 40, 7204-7213. (21) Dubal, D. P.; Ayyad, O.; Ruiz, V.; Gomez-Romero, P. Hybrid Energy Storage: The Merging of Battery and Supercapacitor Chemistries, Chem. Soc. Res. 2015, 44, 1777-1790. (22) Fu, X.; Xia, Z.; Sun, R.; An, H.; Qi, F.; Wang, S.; Liu, Q.; Sun, G. A SelfCharging Hybrid Electric Power Device with High Specific Energy and Power, ACS Energy Lett. 2018, 3, 2425-2432. (23) Zhang, H.; Cao, G.; Wang, W.; Yuan, K.; Xu, B.; Zhang, W.; Cheng, J.; Yang, Y. Influence of Microstructure on The Capacitive Performance of Polyaniline/Carbon Nanotube Array Composite Electrodes, Electrochim. Acta 2009, 54, 1153-1159. (24) Ji, Q.; Yu, D.; Zhang, G.; Lan, H.; Liu, H.; Qu, J. Microfluidic Flow through Polyaniline Supported by Lamellar-Structured Graphene for Mass-Transfer-Enhanced Electrocatalytic Reduction of Hexavalent Chromium, Environ. Sci. Technol. 2015, 49, 1353413541. (25) Piela, P.; Fields, R.; Zelenay, P. Electrochemical Impedance Spectroscopy for Direct Methanol Fuel Cell Diagnostics, J. Electrochem. Soc. 2006, 153, A1902-A1913.


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An Efficient Design for High-Energy and High-Power Capability Hybrid

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