(216c) Transition Metal-Doped C2N as Active Catalysts for the Oxygen Reduction Reaction

Meeting ever-increasing worldwide energy demands in a sustainable way is one of the most pressing challenges of our times. The oxygen reduction reaction (ORR) plays a critical role in pollution-free energy conversion technologies, such as hydrogen fuel cells and metal-air batteries. Platinum (Pt) is one of the best known catalysts for ORR, but the high cost of this precious metal and the sluggish ORR kinetics inhibit the widespread growth and implementation of fuel cell technologies. [1,2]

Two-dimensional (2D) transition metal-doped carbon nitride catalysts have emerged as abundant and low-cost alternatives to Pt for ORR. [3] A more recent member of this family, C₂N, [4] exhibits several promising features for ORR, including a conductive framework and the potential to create and tune active sites through controlled transition metal doping. [5]

In this work, we use density functional theory (DFT) to investigate the ORR mechanism for C₂N catalysts doped with various transition metals. We find that the choice of metal dopant significantly affects the coverages of the ORR intermediates (*OOH, *O, *OH) on this material. These coverages directly influence the predicted ORR mechanism and overpotentials, which determine catalytic activity. By including explicit solvent layers in our predictions, we also investigate solvation effects on the binding energies. By studying the ORR mechanism and activity of various metal-doped C₂N catalysts, we identify critical material properties that influence the performance of single site 2-D catalysts for electrochemical reactions.

References:

[1] Xia, W., Mahmood, A., Liang, Z., Zou, R., & Guo, S. (2016). Earth‐Abundant Nanomaterials for Oxygen Reduction. Angewandte Chemie International Edition, 55(8), 2650-2676.

[2] United States Department of Energy. (2016). Comparison of Fuel Cell Technologies. https://energy.gov/eere/fuelcells/comparison-fuel-cell-technologies.

[3] Zheng, Y. et al. (2017). Molecule-Level g-C₃N₄ Coordinated Transition Metals as a New Class of Electrocatalysts for Oxygen Electrode Reactions. Journal of the American Chemical Society, 139(9), 3336-3339.

[4] Mahmood, J., et. al. (2015). Nitrogenated holey two-dimensional structures. Nature communications, 6, 6486.

[5] Li, X., Zhong, W., Cui, P., Li, J., & Jiang, J. (2016). Design of Efficient Catalysts with Double Transition Metal Atoms on C₂N Layer. The Journal of Physical Chemistry Letters, 7(9), 1750-1755.