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Article

Electrocatalytic Oxygen Reduction Reaction by the Pd/Fe-N-C Catalyst and Application in a Zn–Air Battery

by
Jiabao Chen
,
Zhongqing Wang
,
Chunxiang Yang
,
Guangchao Zou
,
Shuhua Liu
,
Zhiran Sun
,
Lei Wang
,
Rui Li
,
Konggang Qu
,
Wenjun Kang
* and
Haibo Li
*
School of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, China
*
Authors to whom correspondence should be addressed.
Catalysts 2022, 12(12), 1640; https://doi.org/10.3390/catal12121640
Submission received: 6 November 2022 / Revised: 6 December 2022 / Accepted: 12 December 2022 / Published: 14 December 2022
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Abstract

:
Developing a non-platinum catalyst that effectively catalyzes the oxygen reduction reaction (ORR) is highly significant for metal–air batteries. Metal and nitrogen co-doped carbons (M-N-Cs) have emerged as alternative candidates to platinum. In this work, dual-metal Pd/Fe-N-C electrocatalysts were synthesized by the one-step pyrolysis of phytic acid, melamine, and Pd/Fe-based salts. The Pd/Fe-N-C catalyst exhibited a good catalytic ability during the ORR process and outperformed the commercial Pt/C catalyst as regards mass activity, catalytic stability, and methanol tolerance. It was found that Pd-Nx is the active center, and the synergistic effect from the Fe component introduction endowed the Pd/Fe-N-C with an excellent catalytic performance towards the ORR. When assembled into a Zn–air battery, its specific capacity was ~775 mAh gZn−1. Meanwhile, the peak power density could reach 3.85 W mgPd−1, i.e., 3.4 times that of the commercial Pt/C catalyst (1.13 W mgPt−1). This implies that the Pd/Fe-N-C catalyst has potential applications in metal–air batteries.

1. Introduction

Nowadays, the energy crisis and environment degradation promote extensive research on green and renewable energy. Metal–air batteries (e.g., the Zn–air battery) as well as fuel cells are f promising electrochemical devices, which can realize energy conversion with high energy and power density. Unfortunately, the slow kinetic characteristics of the oxygen reduction reaction (ORR), which occurs at the cathode, seriously limits their efficiency; therefore, it is necessary to further boost the ORR activity of catalysts [1]. Platinum-based catalysts, represented by the commercial Pt/C catalyst, exhibit a good ORR activity, but their wide application is highly hindered by the low reserve and high cost of the Pt sources [2,3,4,5,6,7,8]. Palladium (Pd) has very similar atomic size, crystal structure, and electronic structure to those of platinum, indicating its potential application for the ORR. Moreover, its reserve is more abundant, and its price is lower; so, it is a good substitute for platinum catalysts [4,9,10,11,12,13,14].
Since it is reported that cobalt–phthalocyanine has catalytic activity towards the ORR, metal (M) and nitrogen (N) co-doped carbons (M-N-Cs) have also attracted growing attention for their comparable activity to platinum catalysts [15,16,17,18]. In the reported M-N-Cs, M is generally a kind of third transition metal, and Fe is the most active metal species, followed by Co and Mn [19,20,21,22]. It is well known that M-Nx (e.g., M-N4) are ORR active sites [23], on which the adsorption/desorption process for intermediates can be effectively promoted, resulting in a reduced reaction barrier [24,25,26]. Recently, it was found that dual-atoms can provide two anchoring sites for O2 molecules, which results in a weakened O=O bond and favors an efficient four-electron pathway [19]. Therefore, dual-metal M-N-Cs in particular Fe/Co-N-C [27,28,29,30], Fe/Mn-N-C [25], and Fe/Cu-N-C [31,32], have become the focus of attention for their improved ORR catalytic performance. For instance, it was reported that dual-metal Fe/Co-N-C exhibited a much higher catalytic ability than single-metal Fe-N-C and Co-N-C during the ORR process [33].
The universal approach to produce M-N-Cs, consists in the pyrolysis of appropriate carbon-based precursors and transition metal salts in high-temperature conditions [34]. To date, all kinds of precursors have been tried and explored. They can be divided into three categories: (i) carbon materials including carbon black and graphene, which are widely used as precursors; however, additional nitrogen sources such as NH3 should be introduced to construct the M-N-C structure [35,36]; (ii) Polymers that usually contain lots of heteroatoms (e.g., nitrogen), which can work as coordinating sites to anchor metal ions. Under high-temperature conditions, the metal-containing polymers can translate into M-N-C catalysts [37,38]; (iii) Metal–organic frameworks, especially for zeolitic imidazolate frameworks, which have large specific surface area and a high nitrogen percentage, and allow a facile metal atom replacement, which makes them the first choice to synthesize M-N-C catalysts [39].
Although M-N-Cs with transition metal centers have been systematically studied, little attention has concentrated on noble metals. Up to now, there are highly limited studies reported in the ORR catalysis field for noble-metal M-N-C (M = Pt, Pd, and Ru) [40,41,42]. Herein, we report a facile synthesis of the Pd/Fe-N-C catalyst by a one-step pyrolysis approach and investigate the electrocatalytic performance of this catalyst towards the ORR. The obtained Pd/Fe-N-C catalyst outperformed the commercial Pt/C catalyst as regards mass activity, catalytic stability, and methanol resistance. It was found that Pd-Nx is the active center, and the synergistic effect from the Fe component endowed the Pd/Fe-N-C catalyst with an excellent catalytic performance towards the ORR. The Pd/Fe-N-C catalyst also showed a much higher power density than the commercial Pt/C catalyst when it was applied as the cathode catalyst in a Zn–air battery.

2. Results and Discussion

2.1. Catalyst Characterization

Figure 1a illustrates the synthesis procedure for the Pd/Fe-N-C catalyst, which involved the pyrolysis of a solution containing phytic acid, melamine, and Pd/Fe–based salts under an inert atmosphere. Figure 1b shows the XRD diagrams of four catalysts. All XRD patterns presented diffraction peaks at 2θ = 24.5° and 43.7°. By reference to the standard card (JCPDS # 41-1487), the diffraction peaks were attributed to the (002) and (101) crystal planes of graphitic carbons, respectively [12]. The broadness of the peaks implied a poor graphitization degree. No diffraction peaks from Pd- or Fe-related phases (e.g., Pd, Fe, and the PdFe alloy) were observed, apart from the peaks from graphite. The Raman technique was applied to further characterize the carbon component. There were two characteristic peaks located at ~1337 cm−1 and ~1580 cm−1 in the Raman spectra (Figure 1c). The former peak, named D-band, was attributed to the disordered or defected structure of the carbon material, while the latter was due to the sp2 hybridization in graphite, that is, the ordered structure of the carbon material and the in-plane stretching vibration [43,44]. The relative intensity of the two peaks (defined as ID/IG) can reflect the graphitization degree of carbon-based materials. It was found that the calculated values for all catalysts were ~0.95 ± 0.02, indicating a low graphitization degree; these findings were consistent with the XRD results. Although neither a Pd- or a Fe-related phase was observed in the XRD pattern, the EDS characterization confirmed the existence of both Pd and Fe (Figure 1d). Figure 1e,f are high-resolution TEM images of Pd/Fe-N-C, which show an amorphous carbon structure with abundant mesopores. No Pd/Fe-based particles with high contrast were observed in TEM mode. However, further characterization of HAADF-STEM (Figure 1g) along with EDS element mapping confirmed the presence of both Pd and Fe elements, and their distributions well overlapped with those of C, N and P elements (Figure 1h–l). It was concluded that both Pd and Fe were uniformly co-doped into the nitrogen-containing carbon substrates.
The XPS technique can characterize the elemental composition as well as the valence. Figure 2a displays the XPS survey spectrum of Pd/Fe-N-C, revealing the presence of C, N, P, Pd, and Fe elements. The C 1s (Figure 2b) consists of four peaks located at 284.7, 285.6, 287.8, and 291.0 eV, which are related to the C=C/C–C, C=N, C–O, and π-π* bonds, respectively [44,45]. The deconvolution of N 1s (Figure 2c) implied four kinds of N-containing species: M-N, pyrrole-, graphite-, and oxidation-type N, whose peaks are located at 399.3, 400.0, 401.1, and 403.0 eV, respectively [44,46]. The binding energy signals at 132.5 and 133.6 eV belong to P–C and P–O, respectively [47]. Due to the spin–orbital coupling effect, the Pd 3d exhibited double peaks (Figure 2e). Compared with metallic Pd(0), the Pd component in Pd/Fe-N-C has a higher binding energy, which implies that the chemical state of the Pd element is +2. The peak fitting revealed the presence of both Pd(II)–N (337.5 and 342.7 eV) and Pd(II)–Cl (338.7 and 345.1 eV) species [44,48]. The small amount of Cl element derived from K2PdCl4 present in the raw material. Figure 2f shows the peaks of Fe 2p at 723.2, 725.4, 711.1, 714.4, and 718.8 eV, which are related to Fe(II) 2p1/2, Fe(III) 2p1/2, Fe(II) 2p3/2, Fe(III) 2p3/2, as well as a satellite peak, respectively. Notably, the peak at 711.1 eV corresponds to the coordination of Fe-N species [49]. The low content of Fe element complicated the evaluation of the peaks’ positions and the observation of satellite peaks [50]. A similar peak-fitting for other species was also conducted, as shown in Figures S1–S3 in Supplementary Materials (SM). According to the XPS analysis, the Pd weight content in Pd/Fe-N-C and Pd-N-C was 2.5 and 3.0 wt. %, respectively.

2.2. Evaluation of the ORR Catalytic Performance

To assess the ORR activity, cyclic voltammetry (CV) was recorded in an oxygen-saturated potassium hydroxide solution. The appearance of cathode peaks in Figure 3a implied the occurrence of the oxygen reduction reaction, and the peaks’ positions reflect the electrocatalytic ability of the catalysts towards the ORR. For Pd/Fe-N-C, the peak was located at 0.764 V, a value more positive than the values obtained for N-C (0.730 V), Fe-N-C (0.744 V), and Pd-N-C (0.751 V), implying that Pd/Fe-N-C had the highest ORR activity [48]. Linear sweep voltammetry (LSV) was also applied to deeply investigate the ORR performance. Figure 3b shows the LSV curves of Pd/Fe-N-C at different rotations (400~1600 rpm). The reduction currents regularly increased following the rise of the rotating speeds, which implied that O2 molecules could effectively diffuse to the catalyst surface. As an important evaluation index, the electron transfer number (n) was obtained from the Koutecky–Levich (K–L) equation (Equations (S1)–(S3)). The calculated n for Pd/Fe-N-C was 4.0 (Figure 3c), suggesting an efficient four-electron transfer path in the ORR process. Figure 3d displays the LSV curves recorded at 1600 rpm for the four catalysts. Compared with N-C, Fe-N-C exhibited a similar activity; however, Pd-N-C exhibited an obvious improvement. This implies that Pd-Nx is the active center responsible for the ORR activity [51]. It should be noted that the introduction of the Fe component could further improve the ORR activity of Pd-N-C. As exhibited in Figure 3e and Figure S4, Pd/Fe-N-C outperformed the other catalysts as regards both the half-wave potential (E1/2) and the electron transfer number (n), which appeared close to those of the commercial Pt/C (E1/2 = 0.86 V, n = 3.8) (Figure S5). This confirmed that the synergistic effect of Fe introduction was vital for the improvement of the ORR performance of Pd/Fe-N-C [33]. As Pd/Fe-N-C has a low content of Pd, its mass activity can reach 372 mA/mgPd at 0.85 V, which is approximately 2.1 times that of the commercial Pt/C (180 mA/mgPt), showing an application prospect.
Catalytic stability is also an important indicator of the ORR performance and was investigated by the accelerated durability test (ADT) with cyclic voltammetry. As illustrated in Figure 4a,b, the E1/2 of Pd/Fe-N-C negatively shifted by 7 mV after 5000 CV cycles was smaller than that of the commercial Pt/C (25 mV). It means that Pd/Fe-N-C has a much higher catalytic stability. Methanol tolerance is also an important factor that influences a catalyst’s stability. Figure 4c shows the LSV curves of Pd/Fe-N-C before and after adding 1.0 M methanol. Almost no change was observed in the high-potential region. However, an obvious methanol oxidation rather than the ORR took place on the commercial Pt/C catalyst after introducing 1.0 M methanol (Figure 4d). This suggests that the Pd/Fe-N-C catalyst has a better anti-interference performance than the commercial Pt/C. To well evaluate the ORR catalytic process, the kinetic mechanism was studied by the rotating ring-disk electrode (RRDE) test. Figure 4e shows the test results. Compared with the disc current, the ring current for Pd/Fe-N-C was negligible, implying a low yield of the H2O2 product. On the basis of Equations (S4) and (S5), the yield of H2O2 at a high potential (0.60~0.90 V) was less than 5 %, and n was determined to be ~3.9, close to that of the commercial Pt/C (Figure S6). This further confirmed that the ORR on Pd/Fe-N-C proceeded through a high-efficiency four-electron transfer path.

2.3. Zn–Air Battery

In metal–air batteries, the ORR is an important cathode reaction, which highly determines the energy transformation efficiency. Given its high ORR activity, Pd/Fe-N-C was applied as the cathode catalyst in a Zn–air battery. Figure 5a exhibits the schematic diagram of the Zn–air battery, in which a Pd/Fe-N-C-loaded carbon paper and zinc flakes served as the cathode and anode, respectively, and a 6.0 M potassium hydroxide solution was used as the electrolyte. The effective contact area between the electrolyte and the cathode was 1.0 cm2. As shown in Figure 5b, we found that the open circuit voltage (OCV) of Pd/Fe-N-C can reached 1.42 V, close to the reported value (1.43 V) for the commercial Pt/C [52]. Two Pd/Fe-N-C-based Zn–air batteries connected in series could light up an LED board labeled with the LCU logo (Figure 5c). Figure 5d shows the discharge curves at 10 mA cm−2. The output voltage of Pd/Fe-N-C was lower than that of Pt/C in the first stage; however, it surpassed that of Pt/C in a later stage. Both Pd/Fe-N-C- and Pt/C-based Zn–air batteries showed almost the same specific capacity of ~775 mAh gZn−1. Moreover, a similar phenomenon was also observed in a variable-current discharge process. As displayed in Figure 5e, the output voltage of Pd/Fe-N-C remained stable at each current density; however, the voltage platform for the commercial Pt/C showed a declining trend. This further confirmed that the catalytic stability of Pd/Fe-N-C is higher than that of the commercial Pt/C. Figure 5f shows the discharge polarization curve and the corresponding power density of Zn–air batteries driven by Pd/Fe-N-C and Pt/C. The peak power density of Pd/Fe-N-C was 3.85 W mgPd−1 at 316 mA cm−2, i.e., 3.4 times that of the commercial Pt/C (1.13 W mgPt−1 at 307 mA cm−2). It implies a high utilization of metal Pd in Pd/Fe-N-C during the ORR catalytic process.

3. Experimental Section

3.1. Chemicals

Potassium tetrachloropalladate (K2PdCl4), iron chloride hexahydrate (FeCl3·6H2O), phytic acid solution (C6H18O24P6), and melamine (C3H6N6) were purchased from Zhengzhou Alpha Chemical Co., Ltd., Zhengzhou, China. No further purification was carried out for all chemicals.

3.2. Synthesis of Pd/Fe-N-C

Firstly, 100 mg of melamine, 15 mg of K2PdCl4, and 37.2 mg of FeCl3·6H2O were well dispersed in 2 mL of phytic acid (70 wt. % in H2O) by a sonication treatment, and then the solution was carbonized at 950 °C in a N2 atmosphere for 2 h (heating rate: 3 °C min−1). After careful grinding, the obtained powder was fully soaked in 2.0 M hydrochloric acid to remove some impurities. The final product was collected by centrifugation. For convenience, the obtained product was named Pd/Fe-N-C. In addition, Fe-N-C and Pd-N-C were obtained through a similar synthesis process based on the with above procedure. They were prepared in the absence of K2PdCl4 and FeCl3·6H2O, respectively. The N-C counterpart was also synthesized without K2PdCl4 or FeCl3·6H2O.

3.3. Electrochemical Test

The ORR evaluations were performed with a CHI820C potentiostat (Shanghai Chen Hua Co., Shanghai, China) in a 0.1 M KOH solution. An Ag/AgCl (3.0 M NaCl) electrode worked as the reference electrode. The counter electrode was a coiled Pt wire with a length of 23 cm. The working electrodes were fabricated on a rotating disk electrode (RDE) according to the following process: the catalyst powder (2 mg) was dispersed into a solution consisting of 800 µL of H2O, 200 µL of isopropanol, and 10 µL of Nafion (5 wt. %); then, 15 µL of catalyst ink was drop-casted onto the electrode surface.

4. Conclusions

In summary, dual-metal Pd/Fe-N-C was prepared by the one-step pyrolysis of phytic acid, melamine, and Pd/Fe–based salts. The synergistic effect of Fe endowed Pd/Fe-N-C with an excellent ORR performance. In comparison with the commercial Pt/C, Pd/Fe-N-C displayed higher mass activity and catalytic stability as well as a better methanol tolerance. When applied as the cathode catalyst in a Zn–air battery, it also showed a much higher peak power density than the Pt/C catalyst. Given its excellent ORR performance, Pd/Fe-N-C, as a non-platinum catalyst, has promising applications in the metal–air battery field.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal12121640/s1. Characterization techniques for the catalysts; Electrochemical formulas for ORR evaluation; Figure S1: (a) XPS survey spectrum of N-C. Peak-fitting of the XPS spectra of (b) C 1s, (c) N 1s, and (d) P 2p for N-C; Figure S2: Peak-fitting of the XPS spectra of (a) C 1s, (b) N 1s, (c) P 2p, and (d) Fe 2p for Fe-N-C; Figure S3: Peak-fitting of the XPS spectra of (a) C 1s, (b) N 1s, (c) P 2p, and (d) Pd 3d for Pd-N-C; Figure S4: LSV curves of (a) N-C, (b) Fe-N-C, and (c) Pd-N-C in O2-saturated 0.1 M KOH at different rotation rates. Koutecky–Levich plots of (d) N-C, (e) Fe-N-C, and (f) Pd-N-C at different potentials; Figure S5: (a) LSV curves of commercial Pt/C in O2-saturated 0.1 M KOH at different rotation rates. (b) Koutecky–Levich plots of commercial Pt/C at different potentials; Figure S6: (a) Polarization curves of Pt/C recorded on the RRDE in an O2-saturated 0.10 M KOH solution at a rotation rate of 1600 rpm. (b) Calculated H2O2 yield and electron transfer numbers (n) for Pt/C.

Author Contributions

J.C. carried out the main experiments and finished the draft. Z.W., C.Y., G.Z., S.L. and Z.S. performed some electrochemistry experiments. L.W., R.L., K.Q. and W.K. revised the draft. H.L. supervised the work and finalized the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by funds from the Natural Science Foundation of Shandong Province (Grant No. ZR2019MB064, ZR2021MB122, 2019KJC031) and the Students Innovation Fund (Grant No. S202110447063).

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Wu, Y.; Xiao, Z.; Jin, Z.; Li, X.; Chen, Y. The cobalt carbide/bimetallic CoFe phosphide dispersed on carbon nanospheres as advanced bifunctional electrocatalysts for the ORR, OER, and rechargeable Zn-air batteries. J. Colloid Interf. Sci. 2021, 590, 321–329. [Google Scholar] [CrossRef] [PubMed]
  2. Ejaz, A.; Jeon, S. The individual role of pyrrolic, pyridinic and graphitic nitrogen in the growth kinetics of Pd NPs on N-rGO followed by a comprehensive study on ORR. Int. J. Hydrogen Energy 2018, 43, 5690–5702. [Google Scholar] [CrossRef]
  3. Xiang, W.; Zhao, Y.; Jiang, Z.; Li, X.; Zhang, H.; Sun, Y.; Ning, Z.; Du, F.; Gao, P.; Qian, J.; et al. Palladium single atoms supported by interwoven carbon nanotube and manganese oxide nanowire networks for enhanced electrocatalysis. J. Mater. Chem. A 2018, 6, 23366–23377. [Google Scholar] [CrossRef]
  4. Nunes, M.; Fernandes, D.M.; Morales, M.V.; Rodríguez-Ramos, I.; Guerrero-Ruiz, A.; Freire, C. Cu and Pd nanoparticles supported on a graphitic carbon material as bifunctional HER/ORR electrocatalysts. Catal. Today 2020, 357, 279–290. [Google Scholar] [CrossRef]
  5. Fu, Y.; Han, L.; Zheng, P.; Peng, X.; Xian, X.; Liu, J.; Zeng, X.; Dong, P.; Xiao, J.; Zhang, Y. Vanadium nitride supported on N-doped carbon as high-performance ORR catalysts for Zn-air batteries. Catalysts 2022, 12, 877. [Google Scholar] [CrossRef]
  6. Jiang, Y.; Zhu, D.; Zhao, X.; Chu, Z.; Zhang, L.; Cao, Y.; Si, W. Pt/Pd decorate MOFs derived Co-N-C materials as high-performance catalysts for oxygen reduction reaction. Catalysts 2022, 12, 482. [Google Scholar] [CrossRef]
  7. Tang, Z.; Wu, W.; Wang, K. Oxygen reduction reaction catalyzed by noble metal clusters. Catalysts 2018, 8, 65. [Google Scholar] [CrossRef] [Green Version]
  8. Tong, Y.; Wang, L.; Hou, F.; Dou, S.X.; Liang, J. Electrocatalytic oxygen reduction to produce hydrogen peroxide: Rational design from single-atom catalysts to devices. Electrochem. Energy R. 2022, 5, 7. [Google Scholar] [CrossRef]
  9. Liu, H.; Koenigsmann, C.; Adzic, R.R.; Wong, S.S. Probing ultrathin one-dimensional Pd-Ni nanostructures as oxygen reduction reaction catalysts. ACS Catal. 2014, 4, 2544–2555. [Google Scholar] [CrossRef]
  10. Jiao, W.; Chen, C.; You, W.; Zhang, J.; Liu, J.; Che, R. Yolk-shell Fe/Fe4 N@Pd/C magnetic nanocomposite as an efficient recyclable ORR electrocatalyst and SERS substrate. Small 2019, 15, 1805032. [Google Scholar] [CrossRef]
  11. Liu, J.; Fan, X.; Sun, C.Q.; Zhu, W. DFT study on intermetallic Pd-Cu alloy with cover layer Pd as efficient catalyst for oxygen reduction reaction. Materials 2017, 11, 33. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  12. Neergat, M.; Gunasekar, V.; Rahul, R. Carbon-supported Pd-Fe electrocatalysts for oxygen reduction reaction (ORR) and their methanol tolerance. Electroanal. Chem. 2011, 658, 25–32. [Google Scholar] [CrossRef]
  13. Tian, J.; Wu, W.; Tang, Z.; Wu, Y.; Burns, R.; Tichnell, B.; Liu, Z.; Chen, S. Oxygen reduction reaction and hydrogen evolution reaction catalyzed by Pd-Ru nanoparticles encapsulated in porous carbon nanosheets. Catalysts 2018, 8, 329. [Google Scholar] [CrossRef] [Green Version]
  14. Zhou, M.; Guo, J.; Fang, J. Nanoscale design of Pd-based electrocatalysts for oxygen reduction reaction enhancement in alkaline media. Small Struct. 2022, 3, 2100188. [Google Scholar] [CrossRef]
  15. Li, Z.; Zhuang, Z.; Lv, F.; Zhu, H.; Zhou, L.; Luo, M.; Zhu, J.; Lang, Z.; Feng, S.; Chen, W.; et al. The marriage of the FeN4 moiety and MXene boosts oxygen reduction catalysis: Fe 3d electron delocalization matters. Adv. Mater. 2018, 30, 1803220. [Google Scholar] [CrossRef]
  16. Wang, Y.C.; Lai, Y.J.; Song, L.; Zhou, Z.Y.; Liu, J.G.; Wang, Q.; Yang, X.D.; Chen, C.; Shi, W.; Zheng, Y.P.; et al. S-doping of an Fe/N/C ORR catalyst for polymer electrolyte membrane fuel cells with high power density. Angew. Chem. Int. Edit. 2015, 54, 9907–9910. [Google Scholar] [CrossRef]
  17. Xiao, M.; Zhu, J.; Ma, L.; Jin, Z.; Ge, J.; Deng, X.; Hou, Y.; He, Q.; Li, J.; Jia, Q.; et al. Microporous framework induced synthesis of single-atom dispersed Fe-N-C acidic ORR catalyst and its in situ reduced Fe-N4 active site identification revealed by X-ray absorption spectroscopy. ACS Catal. 2018, 8, 2824–2832. [Google Scholar] [CrossRef]
  18. Liu, T.; Zhao, P.; Hua, X.; Luo, W.; Chen, S.; Cheng, G. An Fe-N-C hybrid electrocatalyst derived from a bimetal-organic framework for efficient oxygen reduction. J. Mater. Chem. A 2016, 4, 11357–11364. [Google Scholar] [CrossRef]
  19. He, Y.; Liu, S.; Priest, C.; Shi, Q.; Wu, G. Atomically dispersed metal-nitrogen-carbon catalysts for fuel cells: Advances in catalyst design, electrode performance, and durability improvement. Chem. Soc. Rev. 2020, 49, 3484–3524. [Google Scholar] [CrossRef]
  20. Shen, H.; Gracia-Espino, E.; Ma, J.; Zang, K.; Luo, J.; Wang, L.; Gao, S.; Mamat, X.; Hu, G.; Wagberg, T.; et al. Synergistic effects between atomically dispersed Fe-N-C and C-S-C for the oxygen reduction reaction in acidic media. Angew. Chem. Int. Edit. 2017, 56, 13800–13804. [Google Scholar] [CrossRef]
  21. Xie, X.; He, C.; Li, B.; He, Y.; Cullen, D.A.; Wegener, E.C.; Kropf, A.J.; Martinez, U.; Cheng, Y.; Engelhard, M.H.; et al. Performance enhancement and degradation mechanism identification of a single-atom Co-N-C catalyst for proton exchange membrane fuel cells. Nat. Catal. 2020, 3, 1044–1054. [Google Scholar] [CrossRef]
  22. Pan, Y.; Wang, M.; Feng, C. A doping-adsorption-pyrolysis strategy for constructing atomically dispersed cobalt sites anchored on a N-doped carbon framework as an efficient bifunctional electrocatalyst for hydrogen evolution and oxygen reduction. RSC Adv. 2022, 12, 20578–20582. [Google Scholar] [CrossRef] [PubMed]
  23. Lo Vecchio, C.; Sebastián, D.; Lázaro, M.; Aricò, A.; Baglio, V. Methanol-tolerant M-N-C catalysts for oxygen reduction reactions in acidic media and their application in direct methanol fuel cells. Catalysts 2018, 8, 650. [Google Scholar] [CrossRef] [Green Version]
  24. Xu, W.; Tang, H.; Gu, H.; Xi, H.; Wu, P.; Liang, B.; Liu, Q.; Chen, W. Research progress of asymmetrically coordinated single-atom catalysts for electrocatalytic reactions. J. Mater. Chem. A 2022, 10, 14732–14746. [Google Scholar] [CrossRef]
  25. Sahraie, N.R.; Kramm, U.I.; Steinberg, J.; Zhang, Y.; Thomas, A.; Reier, T.; Paraknowitsch, J.P.; Strasser, P. Quantifying the density and utilization of active sites in non-precious metal oxygen electroreduction catalysts. Nat. Commun. 2015, 6, 8618. [Google Scholar] [CrossRef] [Green Version]
  26. Wang, T.; Sun, C.; Yan, Y.; Li, F. Understanding the active sites of Fe-N-C materials and their properties in the ORR catalysis system. RSC Adv. 2022, 12, 9543–9549. [Google Scholar] [CrossRef]
  27. Shui, H.; Jin, T.; Hu, J.; Liu, H. In situ incorporation strategy for bimetallic FeCo-doped carbon as highly efficient bifunctional oxygen electrocatalysts. ChemElectroChem 2018, 5, 1401–1406. [Google Scholar] [CrossRef]
  28. Zhang, D.; Chen, W.; Li, Z.; Chen, Y.; Zheng, L.; Gong, Y.; Li, Q.; Shen, R.; Han, Y.; Cheong, W.C.; et al. Isolated Fe and Co dual active sites on nitrogen-doped carbon for a highly efficient oxygen reduction reaction. Chem. Commun. 2018, 54, 4274–4277. [Google Scholar] [CrossRef]
  29. Xiong, J.; Chen, X.; Zhang, Y.; Lu, Y.; Liu, X.; Zheng, Y.; Zhang, Y.; Lin, J. Fe/Co/N-C/graphene derived from Fe/ZIF-67/graphene oxide three dimensional frameworks as a remarkably efficient and stable catalyst for the oxygen reduction reaction. RSC Adv. 2022, 12, 2425–2435. [Google Scholar] [CrossRef]
  30. Liu, M.; Li, N.; Cao, S.; Wang, X.; Lu, X.; Kong, L.; Xu, Y.; Bu, X.H. A “pre-constrained metal twins” strategy to prepare efficient dual-metal-atom catalysts for cooperative oxygen electrocatalysis. Adv. Mater. 2022, 34, 2107421. [Google Scholar] [CrossRef]
  31. Wang, Z.; Jin, H.; Meng, T.; Liao, K.; Meng, W.; Yang, J.; He, D.; Xiong, Y.; Mu, S. Fe, Cu-coordinated ZIF-derived carbon framework for efficient oxygen reduction reaction and Zinc-air batteries. Adv. Funct. Mater. 2018, 28, 1802596. [Google Scholar] [CrossRef]
  32. Feng, M.; Wu, X.; Cheng, H.; Fan, Z.; Li, X.; Cui, F.; Fan, S.; Dai, Y.; Lei, G.; He, G. Well-defined Fe-Cu diatomic sites for efficient catalysis of CO2 electroreduction. J. Mater. Chem. A 2021, 9, 23817–23827. [Google Scholar] [CrossRef]
  33. Wang, J.; Huang, Z.; Liu, W.; Chang, C.; Tang, H.; Li, Z.; Chen, W.; Jia, C.; Yao, T.; Wei, S.; et al. Design of N-coordinated dual-metal sites: A stable and active Pt-free catalyst for acidic oxygen reduction reaction. J. Am. Chem. Soc. 2017, 139, 17281–17284. [Google Scholar] [CrossRef] [PubMed]
  34. Wu, H.; Wu, J.; Li, Y.; Li, W.; Zhai, J.; Jiang, Q.; Xu, X.; Gao, Y. Enhanced oxygen reduction with carbon-polyhedron-supported discrete cobalt-nitrogen sites for Zn-air batteries. Chem. Eng. J. 2022, 431, 134084. [Google Scholar] [CrossRef]
  35. Jung, J.Y.; Kim, S.; Kim, J.-G.; Kim, M.J.; Lee, K.-S.; Sung, Y.-E.; Kim, P.; Yoo, S.J.; Lim, H.-K.; Kim, N.D. Hierarchical porous single-wall carbon nanohorns with atomic-level designed single-atom Co sites toward oxygen reduction reaction. Nano Energy 2022, 97, 107206. [Google Scholar] [CrossRef]
  36. Liu, D.; Tong, Y.; Yan, X.; Liang, J.; Dou, S.X. Recent advances in carbon-based bifunctional oxygen catalysts for zinc-air batteries. Batter. Supercaps 2019, 2, 743–765. [Google Scholar] [CrossRef]
  37. Zhu, Z.; Cui, J.; Cao, X.; Yang, L.; Sun, H.; Liang, W.; Li, J.; Li, A. Synthesis and electrocatalytic properties of M (Fe, Co), N co-doped porous carbon frameworks for efficient oxygen reduction reaction. Int. J. Hydrogen Energy 2022, 47, 9504–9516. [Google Scholar] [CrossRef]
  38. Zhu, Y.; Chen, X.; Liu, J.; Zhang, J.; Xu, D.; Peng, W.; Li, Y.; Zhang, G.; Zhang, F.; Fan, X. Rational design of Fe/N/S-doped nanoporous carbon catalysts from covalent triazine frameworks for efficient oxygen reduction. ChemSusChem 2018, 11, 2402–2409. [Google Scholar] [CrossRef]
  39. Gao, C.; Mu, S.; Yan, R.; Chen, F.; Ma, T.; Cao, S.; Li, S.; Ma, L.; Wang, Y.; Cheng, C. Recent advances in ZIF-Derived atomic metal-N-C Electrocatalysts for oxygen reduction reaction: Synthetic strategies, active centers, and stabilities. Small 2022, 18, 2105409. [Google Scholar] [CrossRef]
  40. Wang, Z.; Yang, Y.; Wang, X.; Lu, Z.; Guo, C.; Shi, Y.; Tan, H.; Shen, L.; Cao, S.; Yan, C. A three-dimensional ordered honeycomb nanostructure anchored with Pt-N active sites via self-assembly of a block copolymer: An efficient electrocatalyst towards the oxygen reduction reaction in fuel cells. J. Mater. Chem. A 2022, 10, 12141–12149. [Google Scholar] [CrossRef]
  41. Qin, J.; Liu, H.; Zou, P.; Zhang, R.; Wang, C.; Xin, H.L. Altering ligand fields in single-atom sites through second-shell anion modulation boosts the oxygen reduction reaction. J. Am. Chem. Soc. 2022, 144, 2197–2207. [Google Scholar] [CrossRef] [PubMed]
  42. Chang, J.; Wang, G.; Wang, M.; Wang, Q.; Li, B.; Zhou, H.; Zhu, Y.; Zhang, W.; Omer, M.; Orlovskaya, N.; et al. Improving Pd-N-C fuel cell electrocatalysts through fluorination-driven rearrangements of local coordination environment. Nat. Energy 2021, 6, 1144–1153. [Google Scholar] [CrossRef]
  43. Deng, Y.; Huangfu, H.; Tang, S.; Li, J. High performance ORR electrocatalysts prepared via one-step pyrolysis of riboflavin. Chin. J. Catal. 2017, 38, 1668–1679. [Google Scholar] [CrossRef]
  44. Dong, X.; Li, J.; Wei, D.; Li, R.; Qu, K.; Wang, L.; Xu, S.; Kang, W.; Li, H. Pd(II)/Ni(II)-dimethylglyoxime derived Pd-Ni-P@N-doped carbon hybrid nanocatalysts for oxygen reduction reaction. Appl. Surf. Sci. 2019, 479, 273–279. [Google Scholar] [CrossRef]
  45. Goswami, C.; Saikia, H.; Jyoti Borah, B.; Jyoti Kalita, M.; Tada, K.; Tanaka, S.; Bharali, P. Boosting the electrocatalytic activity of Pd/C by Cu alloying: Insight on Pd/Cu composition and reaction pathway. J. Colloid Interf. Sci. 2021, 587, 446–456. [Google Scholar] [CrossRef]
  46. Chen, C.; Su, H.; Lu, L.-N.; Hong, Y.-S.; Chen, Y.; Xiao, K.; Ouyang, T.; Qin, Y.; Liu, Z.-Q. Interfacing spinel NiCo2O4 and NiCo alloy derived N-doped carbon nanotubes for enhanced oxygen electrocatalysis. Chem. Eng. J. 2021, 408, 127814. [Google Scholar] [CrossRef]
  47. Najam, T.; Shah, S.S.A.; Ding, W.; Jiang, J.; Jia, L.; Yao, W.; Li, L.; Wei, Z. An Efficient Anti-poisoning Catalyst against SOx, NOx, and POx: P, N-doped carbon for oxygen reduction in acidic media. Angew. Chem. Int. Edit. 2018, 57, 15101–15106. [Google Scholar] [CrossRef]
  48. Jiang, X.; Elouarzaki, K.; Tang, Y.; Zhou, J.; Fu, G.; Lee, J.-M. Embedded PdFe@N-carbon nanoframes for oxygen reduction in acidic fuel cells. Carbon 2020, 164, 369–377. [Google Scholar] [CrossRef]
  49. Li, Q.; Liu, H.; Zhang, L.-C.; Chen, H.; Zhu, H.; Wu, Y.; Xu, M.; Bao, S.-J. Highly efficient Fe-N-C oxygen reduction electrocatalyst engineered by sintering atmosphere. J. Power Sources 2020, 449, 227497. [Google Scholar] [CrossRef]
  50. Cai, H.; Chen, B.; Zhang, X.; Deng, Y.; Xiao, D.; Ma, D.; Shi, C. Highly active sites of low spin FeIIN4 species: The identification and the ORR performance. Nano Res. 2020, 14, 122–130. [Google Scholar] [CrossRef]
  51. Han, C.; Yi, W.; Feng, S.; Li, Z.; Song, H. Single-atom palladium anchored N-doped carbon towards oxygen electrocatalysis for rechargeable Zn-air batteries. Dalton Trans. 2022, 51, 12314–12323. [Google Scholar] [CrossRef] [PubMed]
  52. Gu, L.; Sun, X.-L.; Zhao, J.; Gong, B.-Q.; Bao, Z.-L.; Jia, H.-L.; Guan, M.-Y.; Ma, S.-S. A highly efficient bifunctional electrocatalyst (ORR/OER) derived from GO functionalized with carbonyl, hydroxyl and epoxy groups for rechargeable zinc-air batteries. New J. Chem. 2021, 45, 6535–6542. [Google Scholar] [CrossRef]
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Figure 1. (a) Schematic illustration of the synthesis process of Pd/Fe-N-C catalysts. (b) XRD patterns and (c) Raman spectra of N-C, Fe-N-C, Pd-N-C, and Pd/Fe-N-C. (d) EDS of Pd/Fe-N-C. (e,f) High-resolution TEM, (g) HAADF-STEM, and (h–l) EDS element mapping of Pd/Fe-N-C.
Figure 1. (a) Schematic illustration of the synthesis process of Pd/Fe-N-C catalysts. (b) XRD patterns and (c) Raman spectra of N-C, Fe-N-C, Pd-N-C, and Pd/Fe-N-C. (d) EDS of Pd/Fe-N-C. (e,f) High-resolution TEM, (g) HAADF-STEM, and (h–l) EDS element mapping of Pd/Fe-N-C.
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Figure 2. (a) XPS survey spectrum of Pd/Fe-N-C. Peak-fitting of the XPS spectra of (b) C 1s, (c) N 1s, (d) P 2p, (e) Pd 3d, and (f) Fe 2p.
Figure 2. (a) XPS survey spectrum of Pd/Fe-N-C. Peak-fitting of the XPS spectra of (b) C 1s, (c) N 1s, (d) P 2p, (e) Pd 3d, and (f) Fe 2p.
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Figure 3. (a) CV curves of the four catalysts in an O2-saturated 0.1 M KOH solution. (b) LSV curves of Pd/Fe-N-C in an O2-saturated 0.1 M KOH solution at different rotation rates. (c) Koutecky–Levich plots of Pd/Fe-N-C at different potentials. (d) Comparison of the polarization curves of the four catalysts at 1600 rpm. (e) Comparison of the half-wave potential (E1/2) and electron transfer number (n) of the four catalysts. (f) Comparison of the mass activity of the catalysts (M stands for Pd or Pt).
Figure 3. (a) CV curves of the four catalysts in an O2-saturated 0.1 M KOH solution. (b) LSV curves of Pd/Fe-N-C in an O2-saturated 0.1 M KOH solution at different rotation rates. (c) Koutecky–Levich plots of Pd/Fe-N-C at different potentials. (d) Comparison of the polarization curves of the four catalysts at 1600 rpm. (e) Comparison of the half-wave potential (E1/2) and electron transfer number (n) of the four catalysts. (f) Comparison of the mass activity of the catalysts (M stands for Pd or Pt).
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Figure 4. LSV curves before and after the ADT test with 5000 CV cycles for (a) Pd/Fe-N-C and (b) commercial Pt/C. LSV curves before and after the addition of 1.0 M CH3OH for (c) Pd/Fe-N-C and (d) commercial Pt/C. (e) LSV curves recorded on the RRDE for Pd/Fe-N-C in an O2–saturated 0.10 M KOH solution at 1600 rpm. (f) Calculated H2O2 yield and electron transfer numbers (n) for Pd/Fe-N-C.
Figure 4. LSV curves before and after the ADT test with 5000 CV cycles for (a) Pd/Fe-N-C and (b) commercial Pt/C. LSV curves before and after the addition of 1.0 M CH3OH for (c) Pd/Fe-N-C and (d) commercial Pt/C. (e) LSV curves recorded on the RRDE for Pd/Fe-N-C in an O2–saturated 0.10 M KOH solution at 1600 rpm. (f) Calculated H2O2 yield and electron transfer numbers (n) for Pd/Fe-N-C.
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Figure 5. (a) Schematic setup diagram of the Zn–air battery. (b) OCV measurement for the Pd/Fe-N-C-based zinc–air battery. (c) LED board lighted by two Pd/Fe-N-C–based Zn–air batteries. (d) Specific capacities of the Pd/Fe-N-C- and Pt/C-based Zn–air batteries at a current density of 10 mA cm−2. (e) Comparison of the rate capabilities at current densities of 2, 5 and 10 mA cm−2. (f) Discharge polarization curves and power density plots of the Pd/Fe-N-C- and Pt/C-based zinc–air batteries.
Figure 5. (a) Schematic setup diagram of the Zn–air battery. (b) OCV measurement for the Pd/Fe-N-C-based zinc–air battery. (c) LED board lighted by two Pd/Fe-N-C–based Zn–air batteries. (d) Specific capacities of the Pd/Fe-N-C- and Pt/C-based Zn–air batteries at a current density of 10 mA cm−2. (e) Comparison of the rate capabilities at current densities of 2, 5 and 10 mA cm−2. (f) Discharge polarization curves and power density plots of the Pd/Fe-N-C- and Pt/C-based zinc–air batteries.
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Chen, J.; Wang, Z.; Yang, C.; Zou, G.; Liu, S.; Sun, Z.; Wang, L.; Li, R.; Qu, K.; Kang, W.; et al. Electrocatalytic Oxygen Reduction Reaction by the Pd/Fe-N-C Catalyst and Application in a Zn–Air Battery. Catalysts 2022, 12, 1640. https://doi.org/10.3390/catal12121640

AMA Style

Chen J, Wang Z, Yang C, Zou G, Liu S, Sun Z, Wang L, Li R, Qu K, Kang W, et al. Electrocatalytic Oxygen Reduction Reaction by the Pd/Fe-N-C Catalyst and Application in a Zn–Air Battery. Catalysts. 2022; 12(12):1640. https://doi.org/10.3390/catal12121640

Chicago/Turabian Style

Chen, Jiabao, Zhongqing Wang, Chunxiang Yang, Guangchao Zou, Shuhua Liu, Zhiran Sun, Lei Wang, Rui Li, Konggang Qu, Wenjun Kang, and et al. 2022. "Electrocatalytic Oxygen Reduction Reaction by the Pd/Fe-N-C Catalyst and Application in a Zn–Air Battery" Catalysts 12, no. 12: 1640. https://doi.org/10.3390/catal12121640

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