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Sudarshan Vijay: Metal-Nitrogen-Carbon catalysts for CO2 reduction

posted 12 Aug 2019, 07:35 by info admin
DTU Physics, Technical University of Denmark

Graphene based 2D catalysts hold great promise for CO2 reduction to CO and CH4. Recent experimental investigations1 show metal doped Iron-Nitrogen-Carbon (Fe-N-C) catalysts are able to reduce CO2 to CO at low overpotentials and with high selectivity. However, modelling these materials in an electrochemical environment poses several open challenges. In this work, we present a theoretical investigation on Fe-N-C catalysts which includes the effect of potential, interfacial pH, change in local spin states and quantum capacitance to properly elucidate the mechanism for CO2 reduction. Energies are benchmarked to higher levels of theory and experiment to test the applicability of commonly used methods in computational catalysis to these class of materials. We find that the electronic structure of Fe-N-C resembles graphene more than it does a metal, with significantly fewer states at the fermi level. Charge dependence[2] of binding energies of key intermediates depend on the position of the highest energy d-orbital with respect to the fermi level. Using computed reaction energetics coupled with mean-field kinetic models, we are able to ascertain the mechanism for CO2 reduction and compare our results with experimental findings. We extend this analysis to other Metal-Nitrogen-Carbon systems and rational design principles are proposed.  

1. Varela, A. S. et al. Electrochemical reduction of CO2 (CO2RR) on Metal-Nitrogen-doped carbon (MNC) catalysts. ACS Catal. (2019).
2. Gauthier, J. et al. Unified Approach to Implicit and Explicit Solvent Simulations of Electrochemical Reaction Energetics doi:10.26434/chemrxiv.8396954.v1

Sudarshan Vijay is a PhD student at the Catalysis Theory group at the Physics department of the Technical University of Denmark. He works on mechanistic understanding and computational catalyst discovery of CO2 reduction (CO2R) to CO and further reduced products on single atom catalysts on graphene supports. Previously, he obtained his MS from Carnegie Mellon University, Pittsburgh where he worked on using computational methods to elucidate mechanisms at play for transport of hydroxide ions through an anion exchange membrane.