# Facilely synthesized nitrogen-doped reduced graphene oxide functionalized and/or co-doped with metal ions as electrocatalyst for oxygen reduction reaction

Micaela Castellino, Nadia Garino, Juqin Zeng, Adriano Sacco, Francesca Risplendi, Michele Re Fiorentin, Katarzyna Bejtka, Angelica Chiodoni, Jaime Segura-Ruiz, Candido Fabrizio Pirri, et al.

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## ► To cite this version:

Micaela Castellino, Nadia Garino, Juqin Zeng, Adriano Sacco, Francesca Risplendi, et al. Facilely synthesized nitrogen-doped reduced graphene oxide functionalized and/or co-doped with metal ions as electrocatalyst for oxygen reduction reaction. Science Talks, 2022, 4, pp.100073. 10.1016/j.sctalk.2022.100073. hal-05074770

HAL Id: hal-05074770

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Submitted on 20 May 2025

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# Facilely synthesized nitrogen-doped reduced graphene oxide functionalized and/or co-doped with metal ions as electrocatalyst for oxygen reduction reaction

Micaela Castellino<sup>a,*</sup>, Nadia Garino<sup>a,b</sup>, Juqin Zeng<sup>b</sup>, Adriano Sacco<sup>b</sup>, Francesca Risplendi<sup>a</sup>, Michele Re Fiorentin<sup>b</sup>, Katarzyna Bejtka<sup>a,b</sup>, Angelica Chiodoni<sup>b</sup>, Jaime Segura-Ruiz<sup>c</sup>, Candido Fabrizio Pirri<sup>a,b</sup>, Giancarlo Cicero<sup>a</sup>

## ARTICLE INFO

**Keywords:**

Reduced graphene oxide

Oxygen reduction reaction

Surface characterization

Density functional theory calculations

## ABSTRACT

Due to fossil fuels depletion and environmental pollution, clean and sustainable energy technologies, e.g. fuel cells and metal-air batteries, have attracted extensive attention.

To push further the research on these electrochemical devices, low-cost, durable and efficient electrocatalysts alternative to platinum are required, to boost the oxygen reduction reaction (ORR).

A microwave-assisted method has been optimized, to obtain effective heterogeneous catalyst for ORR, starting from graphene oxide (GO), urea and a transition metal (e.g. Mn and Cu) precursor. We have proved that our synthetic method originates porphyrin-like structures containing pyrrole rings within the reduced GO (rGO) basal plane which coordinate the Mn²⁺. In the case of copper, however, Cu²⁺ forms an ionic tetra coordinated structure anchored at the rGO surface via residual oxygen containing functional groups. In both cases, metal complex acts as an ORR highly efficient catalytic reaction center and their identification were strongly supported by several characterization techniques, such as X-ray Photoelectron Spectroscopy (XPS), X-ray absorption spectroscopies (XAS) and Transmission Electron Microscopy (TEM), together with Density Functional Theory (DFT) simulations. All synthesized materials exhibit outstanding catalytic properties toward ORR, as evidenced by electron transfer numbers larger than 3.8 and per-oxide percentages lower than 7%, similar to Pt/C reference electrode.

Video to this article can be found online at https://doi.org/10.1016/
j.sctalk.2022.100073.

<footnote><sup>a</sup> Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy</footnote>

<footnote><sup>b</sup> Center for Sustainable Future Technologies @Polito, Istituto Italiano di Tecnologia, Via Livorno 60, 10144 Torino, Italy</footnote>

<footnote><sup>c</sup> European Synchrotron Radiation Facility, Avenue des Martyrs 71, 38000 Grenoble, France</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: micaela.castellino@polito.it (M. Castellino).</footnote>
Figures and Tables

<figure><img src="image_3.png" /><figcaption>Fig. 1. Schematic illustration of the synthesis of reduced graphene oxide (rGO) starting from commercial graphene oxide (GO) by means of a hydrothermal assisted microwave setup.</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>Fig. 2. XPS HR spectra of Mn2p (a) and Mn3s (b) doublets, C1s (c) and N1s (d) peaks for N-rGO and N-Mn-rGO samples. Image adapted from [1].</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Fig. 3. XANES spectra of (a) Mn metallic foil, MnO2, MnSO4 and Mn-N-rGO powder and their derivative (b). The vertical dotted lines represent the position of the Mn absorption K-edge for the oxidation states 0, +2 and +4 (black, red and blue, respectively). Image adapted from [1].</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>Fig. 4. Mn K edge EXAFS corresponding Fourier transform in R space of the Mn-N-rGO sample. Black line represents experimental data, while red, yellow and blue lines represent the fit procedures obtained using the structures shown in the left side of the figure. The best fit has been obtained with the red line, which represents the Mn atom in a porphyrin-like structure as shown in inset (d).</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Fig. 5. (a) Comparison of electron transfer number (left axis) and peroxide percentage (right axis) evaluated from RRDE measurements. (b) Chronoamperometric curves normalized with respect to the initial current value.</figcaption></figure>
<figure><img src="image_8.png" /><figcaption>**Fig. 6.** Electron microscopy characterization of Cu-N-rGO sample. (a) FESEM micrograph (scale bar: 1 µm), (b) FESEM micrograph (scale bar: 100 nm), (c) BFTEM image (scale bar: 500 nm), (d) STEM micrograph (scale bar: 1 µm), (e) STEM micrograph (scale bar: 100 nm), (f) selected area electron diffraction pattern and (g) EDX spectrum.

Image adapted from [2].</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>Fig. 7. XPS characterization of Cu-N-rGO sample. (a) Survey spectrum, (b) C1s HR spectrum with deconvolution procedure, (c) Cu2p HR doublet and (d) CuLMM Auger peak. Image adapted from [2].</figcaption></figure>

<figure><img src="image_10.png" /><figcaption>Fig. 8. EXAFS study of Cu-N-rGO sample. (a) k3-weighted Cu K edge EXAFS, (b) corresponding Fourier transform in R-space. The solid red lines represent the best fit obtained using the structure of Cu ion coordinated to two surface —O— groups and also bound to hydroxyl groups. Image adapted from [2].</figcaption></figure>
<figure><img src="image_11.png" /><figcaption>Fig. 9. (a) Rotating ring disk electrode study. Number of electrons (left axis) and peroxide percentage (right axis) on graphene-based and reference Pt/C catalysts in air-saturated 0.1 M KOH solution. (b) CA measurements on Cu-N-rGO and reference Pt/C catalysts in air-saturated 0.1 M KOH solution. Image adapted from [2].</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>Fig. 10. XPS survey spectra of Cu-N-rGO sample before (green line) and after (red line) H₂SO₄ treatment.</figcaption></figure>

CRediT author statement

J.Z., A.S., N.G., and G.C. contributed to the conceptualization. C.F.P. contributed to funding acquisition. J.Z., N.G., A.S., M.C., K.B., A.C., F.R., M.R.F., G.C., J.S.-R. contributed to formal analysis and investigation. All authors contributed to writing, review and editing original draft.

Acknowledgments

The CINECA award under the ISCRA initiative and HPC@POLITO are acknowledged for the availability of high performance computing resources and support. The ESRF is acknowledged for the beamtime allocated.

Declaration of interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References

[1] N. Garino, et al., Proving the existence of Mn porphyrin-like complexes hosted in reduced graphene oxide with outstanding performance as oxygen reduction reaction catalysts, 2D Mater. 6 (2019), 045001. https://doi.org/10.1088/2053-1583/ab2449.

[2] N. Garino, et al., Facilely synthesized nitrogen-doped reduced graphene oxide functionalized with copper ions as electrocatalyst for oxygen reduction, npj 2D Mater. Appl. 5 (2021) 2, https://doi.org/10.1038/s41699-020-00185-x.

Further reading

[1] J.A. Trindell, et al., Well-defined nanoparticle electrocatalysts for the refinement of the- ory, Chem. Rev. 120 (2) (2020) https://doi.org/10.1021/acs.chemrev.9b00246 814.

[2] https://ec.europa.eu/info/strategy/priorities-2019-2024/european-green-deal_en.

[3] V. Masson-Delmotte, et al., Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2021.

[4] P.A. Arias, et al., Climate Change, The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, 2021, Cambridge University Press, 2021 33–144.
[5] J.G. Vitillo, et al., The role of carbon capture, utilization, and storage for economic pathways that limit global warming to below 1.5 °C, *iScience* 25 (2022), 104237.

[6] *Proton Exchange Membrane Fuel Cells* - https://doi.org/10.1007/978-3-319-70727-3

[7] https://www.clariant.com/en/Business-Units/Catalysts/Syngas-Catalysts/Fuel-Cell-technologies.

[8] https://www.intechopen.com/chapters/62242.

[9] Y. He, et al., Metal-nitrogen-carbon catalysts for oxygen reduction in PEM fuel cells: self-temperature synthesis approach to enhancing catalytic activity and stability, *Electrochem. Energ. Rev.* 2 (2019) 231–251, https://doi.org/10.1007/s41918-019-00031-9.

[10] N. Garino, et al., Ultrafast, low temperature microwave-assisted solvothermal synthesis of nanostructured lithium iron phosphate optimized by a chemometric approach, *Electrochim. Acta* 184 (2015) 381–386, https://doi.org/10.1016/j.electacta.2015.10.049.

[11] N. Garino, et al., Microwave-assisted synthesis of reduced graphene oxide/SnO2 nano-composite for oxygen reduction reaction in microbial fuel cells, ACS Appl. Mater. Inter-faces 8 (7) (2016) 4633–4643, https://doi.org/10.1021/acsami.5b11198.

[12] N. Garino, et al., One-pot microwave-assisted synthesis of reduced graphene oxide/iron oxide nanocomposite catalyst for the oxygen reduction reaction, *ChemistrySelect* 1 (2016) 3640, https://doi.org/10.1002/slct.201601037.

[13] W. Ju, et al., Understanding activity and selectivity of metal-nitrogen-doped carbon catalysts for electrochemical reduction of CO₂, *Nat. Commun.* 8 (2017) 944, https://doi.org/10.1038/s41467-017-01035-z.

[14] M.C. Biesinger, et al., Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni, *Appl. Surf. Sci.* 257 (2010) 887, https://doi.org/10.1016/j.apsusc.2010.10.051.

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Dr. M. Castellino received her MS and PhD degrees in Physics from the University of Turin (Italy), and now she is Assistant Professor at the Department of Applied Science and Technology at the Polytechnic of Turin (Italy). Her research activity is mainly focused on surface material chemico-physical characterization especially by means of X-ray Photoelectron Spectroscopy (XPS), for energy harvesting and conversion applications. She is main teacher of the “Nanomaterials Engineering” course for the Master Degree in Material Engineering, from 2021. She has published more than 90 journal/conference articles and attended many conferences as invited speaker (1912 citations, h-index = 25 - Scopus source).