More than a Matrix: Tailoring Catalytic Sites in Graphitic Carbon Nitride

Graphitic carbon nitride (g-C3N4) is a promising multifunctional 2D material, especially popular as an eco-friendly and accessible catalyst in oxygen reduction reactions (ORR), hydrogen evolution reactions (HER), and fuel cells [1]. However, the application of g-C3N4 is restricted by a natively high e-/h+ recombination rate, poor conductivity, and low surface area, resulting in somewhat sluggish and limited catalytic performance. Research towards ameliorating these limitations has shown that coordinating metals in the lattice gallery space and non-metal substitutional doping are incredibly effective tools for tailoring selective and high-performing catalytic materials [2]. Critically, these tools are often studied in isolation or with sub-optimally prepared g-C3N4, which fails to address the various challenges holistically [3-5]. Our work demonstrates strong improvements in the baseline performance of g-C3N4 due to pre-polymerization supramolecular assembly coupled with extensive exfoliation. We also show that this g-C3N4 synthesis method is highly compatible for both metals coordinated to the nitrogen lone pairs and substitution covalently bonded dopants. These results show uniquely tailored, catalytically active sites in the material, specifically improving the ORR and HER performance. Specifically, we fabricated exfoliated g-C3N4 nanosheets with transition metals (Fe/Na/Co/Mg/Pd) strongly coordinated to the active sites, which had been secondarily engineered via covalently bonded interstitial dopants (P/S). These materials were subjected to ORR and HER electrochemical assessments and traditional characterization techniques to preliminarily grasp the advantages and limitations of our material preparation procedures. These material variations offer a wide range of selectivity towards catalytic systems and applications while wholistically improving the catalytic performance and preserving the stability, and sustainability of the g-C3N4 system.<br/><br/>Related group papers:<br/>[1] J. Pennings et al., “Femtosecond laser irradiation as a novel method for nanosheet growth and defect generation in g-C3N4,” Nanotechnology, vol. 34, no. 41, p. 415603, Jul. 2023, doi: 10.1088/1361-6528/acda3e.<br/>[2] T. R. Aldhafeeri, M. Uceda, A. Singh, M. Ozhukil Valappil, M. W. Fowler, and M. A. Pope, “Embedded Platinum–Cobalt Nanoalloys in Biomass-Derived Laser-Induced Graphene as Stable, Air-Breathing Cathodes for Zinc–Air Batteries,” ACS Appl. Nano Mater., vol. 6, no. 10, pp. 8302–8314, May 2023, doi: 10.1021/acsanm.3c00564.<br/>[3] G. F. Hawes, S. Rehman, Y. Rangom, and M. A. Pope, “Advanced manufacturing approaches for electrochemical energy storage devices,” International Materials Reviews, vol. 68, no. 3, pp. 323–364, Apr. 2023, doi: 10.1080/09506608.2022.2086388.<br/><br/>Related sources:<br/>[1] J. Wen, J. Xie, X. Chen, and X. Li, “A review on g-C3N4-based photocatalysts,” Applied Surface Science, vol. 391, pp. 72–123, Jan. 2017, doi: 10.1016/j.apsusc.2016.07.030.<br/>[2] A. K. Mrinalini Kalyani, R. Rajeev, L. Benny, A. R. Cherian, and A. Varghese, “Surface tuning of nanostructured graphitic carbon nitrides for enhanced electrocatalytic applications: a review,” Materials Today Chemistry, vol. 30, p. 101523, Jun. 2023, doi: 10.1016/j.mtchem.2023.101523.<br/>[3] Q. Zuo et al., “Ultrathin Metal–Organic Framework Nanosheets with Ultrahigh Loading of Single Pt Atoms for Efficient Visible-Light-Driven Photocatalytic H2 Evolution,” Angewandte Chemie International Edition, vol. 58, no. 30, pp. 10198–10203, 2019, doi: 10.1002/anie.201904058.<br/>[4] J. Jiang et al., “Sulfur-doped g-C3N4/g-C3N4 isotype step-scheme heterojunction for photocatalytic H2 evolution,” Journal of Materials Science & Technology, vol. 118, pp. 15–24, Aug. 2022, doi: 10.1016/j.jmst.2021.12.018.<br/>[5] X. Zhu et al., “Design and Architecture of P-O Co-Doped Porous g-C3N4 by Supramolecular Self-Assembly for Enhanced Hydrogen Evolution,” Catalysts, vol. 12, no. 12, Art. no. 12, Dec. 2022, doi: 10.3390/catal12121583.