Axial chlorine-induced asymmetric cobalt single-atom coordination fields for boosting oxygen reduction reaction
0 Abstract
The development of oxygen reduction reaction (ORR) catalysts with high activity, stability, and economic applicability plays a decisive role in reducing expenses and enhancing the discharge performance of seawater-based zinc-air batteries (SWZABs). Co- and Fe-based single-atom catalysts (M-N4-C) with metal-N4 structure offer advantages of well-defined active structure and high active site utilizations. However, the oxygen electrocatalytic performance of M-N4-C remains a formidable challenge due to the highly stable centrosymmetric electronic structure. To overcome the dilemma, we develop a Co-N4Cl-C with axial coordination of Cl atoms. The axial coordination drags the Co atoms out of the Co-N4 centrosymmetric configuration. This alters the electronic configuration of Co single-atom sites, resulting in a valence state change from +1.83 to +0.67 and forming a localized negative charge environment. These alternations enhance the electronic orbital overlap between Co single-atom sites and oxygen species, promote the rapid evolution of *OOH intermediates, and inhibit the adsorption of toxic Cl- ions, ensuring the ORR kinetics and stability. Co-N4Cl-C exhibits a high oxygen reduction onset potential of 1.05 mV and a half-wave potential of 0.88 mV vs. the reversible hydrogen electrode. The SWZAB, featuring a Co-N4Cl-C catalyst cathode, Zn anode, and NaCl electrolyte supplemented with KOH, reaches a discharge voltage platform of 1.27 V and a peak power density of 179 mW·cm-2, even at a current density
Keywords
INTRODUCTION
The seawater-based zinc-air batteries (SWZABs) exhibit prominent advantages, including low cost, intrinsic safety, and high theoretical energy density[1]. For SWZABs, the oxygen reduction reaction (ORR) constitutes a pivotal electrochemical process[2-4]. The catalytic activity of the cathode significantly dominates key performance indicators of these systems, such as rate capacity, energy density, and operational lifespan[5]. The ORR is characterized by a complex four-electron transfer mechanism that involves multiple steps of proton-coupled electron transfer, which results in slow kinetic rates[6]. The fundamental challenge is that the electronic configuration of the metal sites in the catalytic active centers remains suboptimal, leading to excessively strong or weak adsorption/desorption of the oxygen-species intermediates. Additionally, the suboptimal electronic structure fails to effectively impede the adsorption of Cl- ions in chloride-rich seawater electrolytes, resulting in the poisoning and corrosion of metal active sites and consequently diminishing the operational lifespan[7]. Therefore, the regulation of electronic structure in metal sites is essential for enhancing ORR activity and stability.
Currently, commercial noble metal catalysts (e.g., Pt, Pd) feature an excellent intrinsic electronic structure, demonstrating impressive ORR activity[8]. However, the widespread implementation of these catalysts is restricted by the scarcity of resource distribution and high costs[9]. Moreover, the Co- and Fe-based non-noble metal catalysts with suboptimal electronic structures exhibit strong binding energy with oxygen-containing intermediates, resulting in sluggish kinetic behavior[10-12]. For Co- and Fe-based compounds, including oxides, nitrides, and phosphides, systematic regulation of their electronic structures has been attempted through various strategies, such as doping, vacancies, and strain. However, the performance improvement from these strategies remains limited, which fails to fundamentally address the issue of low intrinsic activity[13-16].
Single-atom catalytic materials with metal-nitrogen (M-N4, M = Co, Fe, etc.) structures present several advantageous characteristics of homogeneous distribution of catalysts, including the uniformity of active sites and the adjustable interactions with ligands, while integrating the significant stability and recyclability of heterogeneous catalysts[17]. Notably, the uniformity of active sites ensures a high proportion of exposed atoms, high active site utilizations, and well-defined active sites at the single-atom level, thereby offering the potential to surpass bulk materials[18]. However, these catalysts typically adopt the M-N4 configuration with a centrosymmetric structure, which tends to exhibit a highly stable electronic structure[19-21]. The stable electronic structure increases the 3d-band electron density of the transition metal single atom, thereby reducing its orbital interaction with O 2p electrons and imposing a higher thermodynamic energy barrier for the generation of the *OOH intermediate[22,23]. Although extensive efforts have been devoted to adjusting the first and second coordination shells, these strategies have demonstrated limited efficacy in altering the centrosymmetric configuration of the M-N4 site[24-27]. The activity of these single-atom catalysts is urgently in need of enhancement[28]. Moreover, the electronic structure of M-N4 configuration with a centrosymmetric structure is insufficient to hinder the adsorption of Cl- ions on Co single-atom sites, which leads to the poisoning of the Co single-atom sites, thereby reducing its stability[29]. Therefore, there is an urgent need to optimize the M-N4 electronic structure of metal single-atom catalysts to achieve both rapid kinetics and strong resistance to Cl- ion poisoning.
In this work, we axially coupled electron-rich and highly electronegative Cl atoms to the Co-N4 coordination structure without altering its tetracoordination, thereby designing the Co-N4Cl-C catalyst. The Co-N4Cl coordination structure consists of a Cl atom coordinated to the Co-N4 structure in an adjacent 2-dimensional (2D) carbon layer. The axial coordination of Cl atoms reconstructs the local electronic environment and optimizes the electronic configuration of the Co single-atom sites, thereby significantly enhancing the intrinsic ORR activity. This axial coordination of Cl transfers electrons to Co single-atom sites, reducing the electron density at the Co site in Co-N4Cl-C from +1.83 to +0.67. The reduction in electron density enhances the orbital coupling between Co single-atom sites and oxygen species, facilitating the generation of *OOH intermediates and thus accelerating the ORR kinetics. This ensures an efficient four-electron transfer mechanism. Meanwhile, the axial coordination of Cl atoms forms a localized negative charge environment, reducing the adsorption of Cl- ions from the reaction medium, mitigating the poisoning of cobalt single-atom sites and thus improving stability. Compared to pristine Co-N4-C, the oxygen reduction onset potential (Eonset) and half-wave potential (E1/2) of Co-N4Cl-C catalyst are enhanced by 0.16 and 0.08 V, respectively, achieving values of 1.05 and 0.88 V vs. reversible hydrogen electrode (RHE). The E1/2 of Co-N4Cl-C surpasses that of Co3O4/G (0.74 V), FeNiP-NPHC (0.83 V), Pt/C-Ir/C
EXPERIMENTAL DETAILS
Materials
Cobalt acetylacetonate [Co(acac)3, 98%], zinc nitrate hexahydrate [Zn(NO3)2·6H2O, 98%], methanol
Fabrication of the Co-ZIF-8 precursor
A 2.60 g quantity of 2-mlm was solubilized in 35 mL of CH3OH, followed by continuous agitation for
Fabrication of the Co-N4-C catalyst
The Co-ZIF-8 precursor underwent pyrolysis at 1,000 °C for a duration of 2 h under an argon gas atmosphere, with a thermal ramp rate of 5 °C per minute, and was then permitted to cool to ambient temperature in a natural manner. The resultant black powder was termed as the Co-N4-C catalyst.
Synthesis of the Co-N4Cl-C catalyst
The Co-ZIF-8 precursor was combined with NaCl powder in a mass proportion of 4:1 and subjected to grinding for 1 h. Subsequently, the mixture was subjected to pyrolysis under a flow of Ar gas at 1,000 °C for a duration of 2 h, with a thermal ramp rate of 5 °C per minute. The resultant black powders were washed with deionized water, separated via centrifugation, and ultimately dried at 60 °C in a vacuum oven for 12 h. The obtained black powders were designated as the Co-N4Cl-C catalyst.
Synthesis of the nitrogen-doped carbon catalyst
A 2.60 g quantity of 2-mlm was solubilized in 35 mL of CH3OH to yield Solution I. Next, 1.20 g of
Characterizations
The X-ray diffraction (XRD, Rigaku, SmartLab XRD) utilizing Cu-Kα radiation was performed to examine the phase constitution. The morphological and microstructural properties were characterized by scanning electron microscope (SEM, Thermo Scientific, Verios G4 UC), transmission electron microscopy (TEM, Thermo Scientific, Talos F200X G2) equipped with energy dispersive spectroscopy (EDS), and high-angle annular dark-field scanning TEM (HAADF-STEM, JEOL, JEM-ARM200F). The quantitative analysis of the Co element content was accomplished through inductively coupled plasma OES spectrometer (ICP-OES, SPECTRO Analytical, SPECTRO-blue). The chemical environment of Co and Cl atoms was scrutinized by X-ray photoelectron spectroscopy measurements (XPS, VG Scientific ESCALAB250). The electronic configuration and coordination structure of Co atom-single sites were probed by X-ray absorption spectroscopy (XAS, easyXAFS, easyXAFS300+). Standard Co foil and CoO powder were deployed as references for Co0 and Co2+ chemical states, respectively. The Co-Pc and CoCl2 were utilized as references for the Co-N and Co-Cl coordination structures, respectively. The obtained extended X-ray absorption fine structure (EXAFS) data were treated in accordance with the standard systemic procedures using the ATHENA module applied in the IFEFFIT software package.
Electrochemical tests
To fabricate the slurry, 10 mg of the catalyst were incorporated into a mixture comprising 80 μL of Nafion (5 wt.%) and 920 μL of isopropanol alcohol, followed by ultrasonication for 1 h. The electrochemical behavior of the ORR was appraised utilizing a conventional three-electrode setup. 4 µL of the paste was applied to a polished glassy carbon electrode, yielding a catalyst loading weight of 0.2 mg·cm-2, which was employed as the working electrode. A Pt foil with an area of 1 cm × 1 cm was engaged as the counter electrode. A Hg/HgO electrode, impregnated with a 1 M KOH solution, was leveraged as the reference electrode. A mixture of 0.5 M NaCl and 1 M KOH was deployed as the electrolyte. All reported potentials were referenced to the RHE using the following expression: Evs.RHE = Evs.Hg/HgO + 0.098 V + 0.059 × pH. The rotating disk electrode (RDE) was interfaced with an electrochemical workstation (Ivium) and a controlled speed rotator (AFMSRCE, Pine Instruments). The ORR polarization curves were captured at a scan rate of
Calculation of electron transfer numbers
Electron transfer numbers (n) were determined using the Koutecky-Levich Equations (1) and (2)[34]:
where J indicates the measured response current density, Jk and JL refer to the kinetic and limiting current densities, ω denotes the angular velocity of the disk, F signifies the Faraday constant (96,500 C·mol-1), n represents the electron transfer numbers throughout ORR process, C0 reflects the bulk concentration of O2 in KOH (1.2 × 10-6 mol·cm-3), D0 means the diffusion coefficient in KOH (1.9 × 10-5 cm2·s-1), and V refers to the kinematic viscosity in the electrolyte (0.1 M KOH: 0.01 cm2·s-1)[35].
Calculation of mass activity and turnover frequency
The value of mass activity (A gmetal-1) was computed by the following Equation (3)[36]:
where Jk and A represent the kinetic current density (mA·cm-2) and the geometric electrode area (cm2), and Mmetal signifies the loading mass of active centers in the electrocatalyst. The Co single-atom sites were regarded as active centers, and their content was validated by ICP-OES testing.
The value of turnover frequency (TOF) was inferred through the Equation (4)[36]:
where Ne refers to the electron number per Coulomb (6.24 × 1018), NA signifies Avogadro’s constant
Fabrication of SWZABs
A solution composed of 6 M KOH and 0.5 M NaCl functioned as a simulated alkaline seawater electrolyte. This electrolyte was maintained in an O2-saturated state over prolonged durations to assess the electrochemical performance of SWZABs. A zinc plate featuring an active area of 1 cm × 1 cm was utilized as the anode. The catalyst was applied to carbon paper to form the air membrane electrode for the cathode, with the catalyst-coated area measuring 1 cm × 1 cm.
RESULTS AND DISCUSSION
The preparation procedure for the Co-N4Cl-C catalyst is schematized in Figure 1. Initially, Co(acac)3 and Zn(NO3)2 interact with 2-mlm to form the Co-ZIF-8 organic ligand. Subsequently, Cl atoms are incorporated into the Co-N4 coordination structure through a molten NaCl-assisted strategy, after which Co-N4Cl-C is obtained. For comparison, the synthesis process for the Co-N4-C catalyst is identical to that of Co-N4Cl-C, except for the exclusion of NaCl.
Figure 1. Visual representation of the synthetic procedures for the Co-N4Cl-C catalyst. 2-mlm: 2-methylimidazole.
The morphological characteristics of Co-N4-C and Co-N4Cl-C were first examined using SEM and TEM. The Co-N4-C catalyst exhibits a solid dodecahedral morphology, with particles observed to be approximately 80 nm after pyrolysis [Figure 2A and B], which is similar to the Co-ZIF-8 precursor [Supplementary Figure 1]. In contrast, with the molten NaCl-assisted strategy, the dodecahedral structure of Co-N4Cl-C undergoes slight collapse, shrinking to a size of 50 nm [Figure 2C and D]. Meanwhile, the dodecahedral configuration evolves from a solid structure into a porous hollow carbon skeleton [Figure 2D]. The formation of the porous hollow carbon framework is attributed to the high polarity of NaCl, which melts and infiltrates the Co-ZIF-8 dodecahedral structure during pyrolysis[37-39]. This process induces localized etching between adjacent C and Cl atoms, generating pores and facilitating the introduction of Cl atoms. EDS mapping was employed to verify the spatial distribution of multiple elements within the catalyst. The comparison of EDS mapping results [Figure 2E and F] ascertains that C, N, Co, and additional Cl elements are evenly dispersed throughout the Co-N4Cl-C, while C atoms are enriched in edge regions. Based on the fitting curves of the EDS spectrum, the content of Cl atoms in the Co-N4Cl-C catalyst was determined to be 0.17 wt.% [Supplementary Figure 2]. The Cl content is significantly lower than the nominal concentration, showing that most Cl atoms are volatilized during 1,000 °C pyrolysis, leaving only trace residues. To clarify the specific localization of Co atoms on the carbon substrate, the HAADF-STEM test was conducted. The isolated bright spots attest to the monatomic distribution of Co atoms in Co-N4-C
Figure 2. (A and C) The SEM pictures; (B and D) TEM pictures; (E and F) corresponding EDS mappings; and (G and H) HAADF-STEM images of Co-N4-C and Co-N4Cl-C, respectively. SEM: Scanning electron microscope; TEM: transmission electron microscopy; EDS: energy dispersive spectroscopy; HAADF-STEM: high-angle annular dark-field scanning TEM.
The XPS detection technology was performed to reveal the surface chemical environment of catalysts. In the high-resolution Cl 2p spectra [Figure 3A], the prominent characteristic peak is observed at 197 eV for Co-N4Cl-C[42]. For the high-resolution Co 2p spectra [Supplementary Figure 5] of Co-N4-C and Co-N4Cl-C catalysts, peaks are observed at 778.8 and 793.6 eV, which are characteristics of the Co0 2p3/2 and Co0 2p1/2 orbitals, respectively. Prominent peaks at 780.7 and 795.6 eV are indicative of the oxidation status of the Co2+ 2p3/2 and Co2+ 2p1/2 orbitals, respectively. Moreover, satellite peaks are identified at 785.3 and
Figure 3. (A) Cl 2p XPS spectra of Co-N4-C and Co-N4Cl-C; (B) Co-K-edge XANES spectra of samples and references (the inset shows the magnified pre-edge XANES region); (C) The determined Co K-edge positions and oxidation statuses of Co in the Co-N4Cl-C and Co-N4-C; (D) FT of the EXAFS spectra of samples and references. First-shell fitting of FT of EXAFS spectra for (E) Co-N4-C and (F) Co-N4Cl-C. EXAFS spectra were fitted using the FEFF 6.0 code (the insets show the structure of the Co-N4-C and Co-N4Cl-C; the balls in gray, blue, pink, and green correspond to C, N, Co, and Cl atoms, respectively); (G) WT of samples and references. XPS: X-ray photoelectron spectroscopy; XANES: X-ray absorption near-edge structure; EXAFS: extended X-ray absorption fine structure; FT: Fourier transform; FEFF: full multiple scattering; WT: wavelet-transformed.
The K3-weighted EXAFS spectra were derived from the Fourier-transformed (FT) original XAS data. In the first shell of the R-space between 1 and 2 Å, the characteristic peak of Co-N4-C emerges at 1.4 Å, similar to that in Co-Pc, corresponding to the Co-N4 coordination structure [Figure 3D][44]. By contrast, this characteristic peak for Co-N4Cl-C shifts to 1.7 Å, resulting in a change in the first-shell coordination environment of Co metal sites. Moreover, in the Co-N4-C and Co-N4Cl-C catalysts, neither the characteristic peaks associated with Co-Co and Co-O scattering paths are detected in the second shell of the R-space spectra within the range of 2 to 2.5 Å, indicating that the metal coordination structure consists solely of Co single-atom sites[45,46]. To further elucidate the coordination number and bond length of Co single-atom sites, the EXAFS curves were quantitatively analyzed using fitting routines [Figure 3E and F]. Compared with Co-N4-C, in the first coordination shell, the Co-N coordination number of Co-N4Cl-C catalyst evolves from 4.1 to 3.6, and the Co-Cl coordination number is calculated to be 0.9 [Supplementary Table 2][22,47]. Notably, the generation of the Co-Cl coordination structure stretches the Co-N bond length to 1.7 Å, bringing both to a comparable scale. Additional insights into the atomic arrangement of Co are provided by the EXAFS oscillation curves in k-space [Supplementary Figure 6] and wavelet-transformed (WT) Co K-edge EXAFS contour plots [Figure 3G]. The intensity maxima of the Co-N4-C and Co-N4Cl-C catalysts appear at 6.5 and 6.2 Å-1, corresponding to Co-N and Co-N/Cl scattering paths, respectively, consistent with the structural analysis of R-space. Based on these XAS results, the structure of Co-N4Cl-C involves the formation of an axial coordination structure between individual Cl atoms and Co single-atom site in the adjacent 2D carbon layer, pulling the Co atom away from the planar centrosymmetric Co-N4 environment [Figure 3F, inset]. This pulling process induces a tip effect, which triggers the accumulation of local negative charges and results in partial electron transfer from the chlorine atoms to the cobalt single-atom sites, thereby reducing the valence state of the cobalt single-atom sites[48,49].
To evaluate the benefit of Cl atomic axial coordination, the ORR performances of Co-N4Cl-C, Co-N4-C, NC, and commercial Pt/C catalysts were systematically examined in 1 M KOH and 0.5 M NaCl electrolyte. The conventional three-electrode setup was employed for electrochemical measurements. This setup includes the catalyst as the working electrode, a Pt foil as the counter electrode, and an Hg/HgO electrode (saturated with 1 M KOH) as the reference electrode. In the linear sweep voltammetry (LSV) analysis conducted on the RDE at a scan rate of 5 mV·s-1 under a spinning rate of 1,600 rpm in N2-saturated and O2-saturated conditions, over a potential span of 0.2 to 1.2 V vs. RHE, the current densities of the Co-N4-C, Co-N4Cl-C, Pt/C, and NC catalysts show a notable increase under O2-saturated condition relative to those under N2-saturated condition [Figure 4A and Supplementary Figure 7], demonstrating the occurrence of ORR process rather than other electrochemical reactions (such as double-layer capacitance, ion intercalation, and hydrogen evolution). After background calibration using the current densities of LSV curves under N2-saturated conditions, the Co-N4Cl-C catalyst delivers oxygen reduction Eonset and E1/2 of 1.05 and 0.88 V vs. RHE, outperforming the Co-N4-C (0.89 and 0.8 V), Pt/C (0.94 and 0.85 V), and NC (0.76 and 0.71 V). Meanwhile, the E1/2 of Co-N4Cl-C is higher than that of most reported catalysts in seawater-based systems, such as Co3O4/G (0.74 V), FeNiP-NPHC (0.83 V), Pt/C-Ir/C (0.85 V), D-FeCo@NHC (0.85 V), and FexN-NC (0.87 V) [Figure 4B][30-33]. As shown in Figure 4C, the Co-N4-C, Pt/C, and NC catalysts exhibit the Tafel slopes of 103, 87, and 143 mV·dec-1, respectively. In contrast, the Co-N4Cl-C catalyst demonstrates the smallest Tafel slope (76 mV·dec-1), pointing to faster oxygen electrocatalytic reaction kinetics. The TOF and mass activity of Co-N4Cl-C and Co-N4-C were calculated at 0.80 V vs. RHE, which serve as key indicators of intrinsic catalytic activity [Figure 4D]. The Co-N4Cl-C catalyst exhibits a mass activity of 1,713 A·g-1 and a TOF of 15.72 h-1, both of which are approximately 2.5-fold greater than those of Co-N4-C (680 A·g-1 and
Figure 4. (A) LSV tests of Co-N4-C, Co-N4Cl-C, Pt/C, and NC collected after the electrolyte is saturated with O2; (B) Literature comparison chart about ORR performance of Co-N4Cl-C with reported catalysts; (C) Tafel plots of Co-N4-C, Co-N4Cl-C, Pt/C, NC; (D) Mass activity and TOF at 0.80 V (vs. RHE) for Co-N4-C and Co-N4Cl-C catalysts. ORR polarization curves of (E) Co-N4Cl-C and (F) Co-N4-C at various rotational speeds; the inset shows a fitting illustration of the K-L formula across various voltages; (G) Current-time chronoamperometric responses of Co-N4Cl-C, Co-N4-C, and Pt/C. LSV: Linear sweep voltammetry; ORR: oxygen reduction reaction; TOF: turnover frequency.
The remarkable ORR activity of Co-N4Cl-C highlights its potential as a high-performance cathode for SWZABs. The SWZAB was assembled using the Co-N4Cl-C-based membrane electrode as the cathode and a zinc plate as the anode. Its practical charge/discharge characteristics were appraised in a simulated alkaline seawater electrolyte of 0.5 M NaCl and 6 M KOH. The open-circuit voltage (OCV) is determined to be
Figure 5. (A) OCV plots of SWZABs assembled with Co-N4Cl-C, Co-N4-C, and Pt/C catalysts using simulated alkaline seawater electrolyte (6 M KOH and 0.5 M NaCl); (B) Discharge polarization curves and power density plots of Co-N4Cl-C-, Co-N4-C-, and Pt/C-based SWZABs; (C) Specific capacity by mass normalization at a constant current density of 10 mA·cm-2; (D) Galvanostatic discharge curves at various current densities ranging from 3 to 20 cm-2. OCV: Open-circuit voltage; SWZABs: seawater-based zinc-air batteries.
CONCLUSIONS
In summary, we incorporated Cl atoms into the Co-N4 coordination structure, developing the Co-N4Cl-C catalyst as a high-performance ORR cathode for SWZABs. The Cl atom acts as an electron-rich and highly electronegative anionic ligand, which forms an axial coordination structure of Co-N4Cl with Co single-atom sites in the neighboring 2D carbon layer. This axial coordination drags the original planar centrosymmetric Co-N4 structure and stretches the bond length of Co-N, transferring electrons to the Co metal site and adjusting its charge state from +1.83 to +0.67 due to the accumulation of local negative charges caused by tip effect. The reduction in charge density boosts electronic orbital overlap between Co single-atom sites and oxygen species, thereby accelerating ORR kinetics during the conversion of *OOH intermediates. Meanwhile, the axial coordination of Cl atoms induces a localized negative charge environment on the surface of Co single atom sites, impeding the adsorption poisoning of Cl- atoms. These alternations result in high intrinsic activity and stability of Co-N4Cl-C in the alkaline seawater medium. The Co-N4Cl-C catalyst exhibits E1/2 of 0.88 V (vs. RHE), surpassing the values of Co3O4/G (0.74 V), FeNiP-NPHC (0.83 V),
DECLARATIONS
Authors’ contributions
The conception and design of the work: Zheng, X.R.; Deng, Y.D.
The acquisition and analysis of data: Jiang, X.R.; Lu, J.D.; Xie, G.D.; Li, J.H.
The interpretation of data: Jiang, X.R.; Dong, Y.; Xie, P.; Ma, W.D.
The supervision: Huang, W.J.; Zheng, X.R.; Lu, J.D.
All authors participated in writing the manuscript.
Availability of data and materials
The data and materials can be obtained from the corresponding author upon reasonable request.
Financial support and sponsorship
This work was supported by the National Natural Science Foundation of China (No. U23A20687, No. 52422314, No. 52402357) and the Hainan Provincial Natural Science Foundation of China (No. KJRC2023L04).
Conflicts of interest
Yida Deng is an Editorial Board member of the journal Microstructures. Yida Deng was not involved in any steps of editorial processing, notably including reviewer selection, manuscript handling, and decision making. The other authors declared that there are no conflicts of interest.
Ethical approval and consent to participate
Not applicable.
Copyright
© The Author(s) 2025.
Supplementary Materials
REFERENCES
1. Yu, J.; Li, B. Q.; Zhao, C. X.; Zhang, Q. Seawater electrolyte-based metal-air batteries: from strategies to applications. Energy. Environ. Sci. 2020, 13, 3253-68.
2. Wang, Q.; Kaushik, S.; Xiao, X.; Xu, Q. Sustainable zinc-air battery chemistry: advances, challenges and prospects. Chem. Soc. Rev. 2023, 52, 6139-90.
3. Guo, Y.; Cao, Y.; Lu, J.; Zheng, X.; Deng, Y. The concept, structure, and progress of seawater metal-air batteries. Microstructures 2023, 3, 2023038.
4. Zheng, L.; Chang, L.; Xue, S.; et al. Electrochemical responsive alginate chains rendered sol-to-gel gradient electrolyte towards practical Ah-level zinc metal pouch cell. Angew. Chem. Int. Ed. Engl. 2025, 64, e202502103.
5. Ju, L.; Tang, X.; Kou, L. Polarization boosted catalysis: progress and outlook. Microstructures 2022, 2, 2022008.
6. Dey, S.; Mondal, B.; Chatterjee, S.; Rana, A.; Amanullah, S. K.; Dey, A. Molecular electrocatalysts for the oxygen reduction reaction. Nat. Rev. Chem. 2017, 1, 0098.
7. Zhan, Y.; Ding, Z. B.; He, F.; et al. Active site switching of Fe-N-C as a chloride-poisoning resistant catalyst for efficient oxygen reduction in seawater-based electrolyte. Chem. Eng. J. 2022, 443, 136456.
8. Zhang, J.; Yuan, Y.; Gao, L.; Zeng, G.; Li, M.; Huang, H. Stabilizing Pt-based electrocatalysts for oxygen reduction reaction: fundamental understanding and design strategies. Adv. Mater. 2021, 33, e2006494.
9. Li, Y.; Liang, J.; Lin, Z.; et al. Introducing covalent metal-phosphorus bonds into intermetallic platinum-based catalysts for high-performance fuel cells. Renewables 2024, 2, 223-32.
10. Zeng, K.; Zheng, X.; Li, C.; et al. Recent advances in non-noble bifunctional oxygen electrocatalysts toward large-scale production. Adv. Funct. Mater. 2020, 30, 2000503.
11. Osgood, H.; Devaguptapu, S. V.; Xu, H.; Cho, J.; Wu, G. Transition metal (Fe, Co, Ni, and Mn) oxides for oxygen reduction and evolution bifunctional catalysts in alkaline media. Nano. Today. 2016, 11, 601-25.
12. Han, X.; He, G.; He, Y.; et al. Metal air batteries: engineering catalytic active sites on cobalt oxide surface for enhanced oxygen electrocatalysis. Adv. Energy. Mater. 2018, 8, 1870043.
13. Pu, Z.; Liu, T.; Amiinu, I. S.; et al. Transition-metal phosphides: activity origin, energy-related electrocatalysis applications, and synthetic strategies. Adv. Funct. Materials. 2020, 30, 2004009.
14. Tian, D.; Denny, S. R.; Li, K.; Wang, H.; Kattel, S.; Chen, J. G. Density functional theory studies of transition metal carbides and nitrides as electrocatalysts. Chem. Soc. Rev. 2021, 50, 12338-76.
15. Maiti, S.; Maiti, K.; Curnan, M. T.; Kim, K.; Noh, K.; Han, J. W. Engineering electrocatalyst nanosurfaces to enrich the activity by inducing lattice strain. Energy. Environ. Sci. 2021, 14, 3717-56.
16. Hu, X.; Tian, W.; Wu, Z.; Li, X.; Li, Y.; Wang, H. Synthesis of Zr2ON2 via a urea-glass route to modulate the bifunctional catalytic activity of NiFe layered double hydroxide in a rechargeable zinc-air battery. J. Colloid. Interface. Sci. 2024, 672, 610-7.
17. Poudel, M. B.; Balanay, M. P.; Lohani, P. C.; Sekar, K.; Yoo, D. J. Atomic engineering of 3D self-supported bifunctional oxygen electrodes for rechargeable zinc-air batteries and fuel cell applications. Adv. Energy. Mater. 2024, 14, 2400347.
18. 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, 3484-524.
19. Yuan, L. J.; Sui, X. L.; Pan, H.; Wang, Z. B. Strategies and mechanism for enhancing intrinsic activity of metal-nitrogen-carbon catalysts in electrocatalytic reactions. Renewables 2023, 1, 514-40.
20. Shang, H.; Zhou, X. L.; Dong, J.; Wang, Z. Engineering unsymmetrically coordinated Cu-S1N3 single atom sites with enhanced oxygen reduction activity. Nat. Commun. 2020, 11, 3049.
21. Mun, Y.; Lee, S.; Kim, K.; et al. Versatile strategy for tuning ORR activity of a single Fe-N4 site by controlling electron-withdrawing/donating properties of a carbon plane. J. Am. Chem. Soc. 2019, 141, 6254-62.
22. Liu, M.; Zhang, J.; Su, H.; et al. In situ modulating coordination fields of single-atom cobalt catalyst for enhanced oxygen reduction reaction. Nat. Commun. 2024, 15, 1675.
23. Grimaud, A.; Demortière, A.; Saubanère, M.; et al. Activation of surface oxygen sites on an iridium-based model catalyst for the oxygen evolution reaction. Nat. Energy. 2016, 2, 1-10.
24. Wang, A.; Li, J.; Zhang, T. Heterogeneous single-atom catalysis. Nat. Rev. Chem. 2018, 2, 65-81.
25. Zhou, A. W.; Wang, D. S.; Li, Y. D. Hollow microstructural regulation of single-atom catalysts for optimized electrocatalytic performance. Microstructures 2022, 2, 2022005.
26. Wang, Z.; Niu, H.; Wu, T.; Ding, S.; Yu, X. B.; Su, Y. Periodic defect boundary-mediated activity of electrocatalytic oxygen reduction reactions of Fe-N-C catalysts. Renewables 2024, 3, 213-9.
27. Wang, W.; Hu, Y.; Li, P.; Liu, Y.; Chen, S. Realizing the 4e-/2e- pathway transition of O2 reduction on Co-N4-C catalysts by regulating the chemical structures beyond the second coordination shells. ACS. Catal. 2024, 14, 5961-71.
28. Datye, A. K.; Guo, H. Single atom catalysis poised to transition from an academic curiosity to an industrially relevant technology. Nat. Commun. 2021, 12, 895.
29. Liu, Y.; Feng, S.; Shan, L.; et al. Localized negatively charged interfaces for seawater electrolyte-based zinc-air batteries. Adv. Funct. Materials. 2025, 35, 2422874.
30. Yu, J.; Zhao, C. X.; Liu, J. N.; Li, B. Q.; Tang, C.; Zhang, Q. Seawater-based electrolyte for zinc-air batteries. GreenChE 2020, 1, 117-23.
31. Yu, Q.; Liu, X.; Liu, G.; et al. Constructing three-phase heterojunction with 1D/3D hierarchical structure as efficient trifunctional electrocatalyst in alkaline seawater. Adv. Funct. Materials. 2022, 32, 2205767.
32. Wu, S.; Liu, X.; Mao, H.; et al. Realizing high-efficient oxygen reduction reaction in alkaline seawater by tailoring defect-rich hierarchical heterogeneous assemblies. Appl. Catal. B-Environ. 2023, 330, 122634.
33. Wu, S.; Liu, X.; Mao, H.; et al. Unraveling the tandem effect of nitrogen configuration promoting oxygen reduction reaction in alkaline seawater. Adv. Energy. Mater. 2024, 14, 2400183.
34. Luo, Y.; Li, K.; Hu, Y.; et al. TiN as radical scavenger in Fe-N-C aerogel oxygen reduction catalyst for durable fuel cell. Small 2024, 20, e2309822.
35. Meng, R.; Zhang, C.; Lu, Z.; et al. An oxygenophilic atomic dispersed Fe-N-C catalyst for lean-oxygen seawater batteries. Adv. Energy. Mater. 2021, 11, 2170085.
36. Zhang, J.; Liu, M.; Zhang, Y.; et al. Tandem synergetic effect in symbiotic Co catalyst for enhanced oxygen reduction. Chem. Eng. J. 2025, 505, 159687.
37. Zhang, W.; Zhang, J.; Wang, N.; et al. Two-electron redox chemistry via single-atom catalyst for reversible zinc-air batteries. Nat. Sustain. 2024, 7, 463-73.
38. Wang, K.; Lu, Z.; Lei, J.; Liu, Z.; Li, Y.; Cao, Y. Modulation of ligand fields in a single-atom site by the molten salt strategy for enhanced oxygen bifunctional activity for zinc-air batteries. ACS. Nano. 2022, 16, 11944-56.
39. Feng, X.; Chen, G.; Cui, Z.; et al. Engineering electronic structure of nitrogen-carbon sites by sp3-hybridized carbon and incorporating chlorine to boost oxygen reduction activity. Angew. Chem. Int. Ed. Engl. 2024, 63, e202316314.
40. Tian, H.; Ma, Y.; Li, Z.; et al. Disorder-tuned conductivity in amorphous monolayer carbon. Nature 2023, 615, 56-61.
41. Cui, J.; Zhang, D.; Liu, Z.; et al. Carbon-anchoring synthesis of Pt1Ni1@Pt/C core-shell catalysts for stable oxygen reduction reaction. Nat. Commun. 2024, 15, 9458.
42. Zhang, H.; Guo, H.; Li, D.; et al. Halogen doped graphene quantum dots modulate TDP-43 phase separation and aggregation in the nucleus. Nat. Commun. 2024, 15, 2980.
43. Huang, Y.; Zhu, K.; Hu, Z.; et al. Solvent-free synthesis of foam board-like CoSe2 alloy to selectively generate singlet oxygen via peroxymonosulfate activation for sulfadiazine degradation. J. Hazard. Mater. 2024, 466, 133611.
44. Su, J.; Musgrave, C. B.; Song, Y.; et al. Strain enhances the activity of molecular electrocatalysts via carbon nanotube supports. Nat. Catal. 2023, 6, 818-28.
45. Kumar, P.; Kannimuthu, K.; Zeraati, A. S.; et al. High-density cobalt single-atom catalysts for enhanced oxygen evolution reaction. J. Am. Chem. Soc. 2023, 145, 8052-63.
46. Ye, P.; Fang, K.; Wang, H.; et al. Lattice oxygen activation and local electric field enhancement by co-doping Fe and F in CoO nanoneedle arrays for industrial electrocatalytic water oxidation. Nat. Commun. 2024, 15, 1012.
47. Ding, S.; Barr, J. A.; Shi, Q.; et al. Engineering atomic single metal-FeN4Cl sites with enhanced oxygen-reduction activity for high-performance proton exchange membrane fuel cells. ACS. Nano. 2022, 16, 15165-74.
48. Liu, P.; Chen, B.; Liang, C.; et al. Tip-enhanced electric field: a new mechanism promoting mass transfer in oxygen evolution reactions. Adv. Mater. 2021, 33, e2007377.
49. Khan, M. U.; Wang, L.; Liu, Z.; et al. Pt3Co octapods as superior catalysts of CO2 hydrogenation. Angew. Chem. Int. Ed. Engl. 2016, 55, 9548-52.
50. Zhang, L.; Jin, N.; Yang, Y.; et al. Advances on axial coordination design of single-atom catalysts for energy electrocatalysis: a review. Nanomicro. Lett. 2023, 15, 228.
Cite This Article
Open AccessHow to Cite
Download Citation
Export Citation File:
Type of Import
Tips on Downloading Citation
Citation Manager File Format
Type of Import
Direct Import: When the Direct Import option is selected (the default state), a dialogue box will give you the option to Save or Open the downloaded citation data. Choosing Open will either launch your citation manager or give you a choice of applications with which to use the metadata. The Save option saves the file locally for later use.
Indirect Import: When the Indirect Import option is selected, the metadata is displayed and may be copied and pasted as needed.
About This Article
Copyright
Data & Comments
Data
0
Comments
Comments must be written in English. Spam, offensive content, impersonation, and private information will not be permitted. If any comment is reported and identified as inappropriate content by OAE staff, the comment will be removed without notice. If you have any queries or need any help, please contact us at support@oaepublish.com.