Electrocatalytic production of ammonia from dinitrogen is considered as a sustainable alternative to the energy-demanding and pollutive Haber-Bosch process [1]. A promising class of materials for selective reduction of nitrogen (NRR) corresponds to MXenes, however, with the caveat that these materials have shown to be effective catalysts for the competing hydrogen evolution reaction (HER) in the same potential range [2]. A better atomic-scale understanding of the NRR requires theoretical approaches that go beyond the traditional volcano approach [3]. Therefore, different mechanistic pathways as well as overpotential and kinetic effects must be taken into account when analyzing activity trends by means of heuristic approaches [4,5].

In this lecture, we present our recent results gained by the combination of density functional theory calculations and molecular dynamics simulations for nanoscale MXene compositions [6]. Using a dedicated procedure of electrochemical in silico pulse experiments, we discuss the formation of single-atom catalysts based on MXenes. Notably, the single-atom motif of MXenes reveals excellent activity and selectivity for the electrocatalytic NRR, and we identify the reaction mechanism and limiting reaction steps for this motif by our advanced in-house methodologies [7].

References:

[1] C. Guo et al., Energy Environ. Sci. 2018, 14, 45-56.

[2] Z. W. Seh et al., ACS Energy Lett. 2016, 1, 589-594.

[3] K. S. Exner, Chin. J. Catal. 2022, 43, 2871-2880.

[4] K. S. Exner, ChemCatChem 2022, 14, e202200366

[5] S. Razzaq, K. S. Exner, ACS Catal. 2023, 13, 1740-1758.

[6] S. Razzaq, S. Faridi, D. Singh, S. Kenmoe, L. Meng, F. Vines, F. Illas, K. S. Exner, submitted.

[7] D. Singh, S. Razzaq, K. S. Exner, submitted.