(389i) Designing M-N-C Electrocatalysts with Inspiration from Thermal and Molecular Catalysis
AIChE Annual Meeting
2022
2022 Annual Meeting
Engineering Sciences and Fundamentals
Electrochemical Fundamentals: Faculty Candidate Session II
Tuesday, November 15, 2022 - 5:00pm to 5:15pm
In the first example,1 the mechanism of O2 reduction mediated by hydroquinone (HQ) molecules is studied over M-N-Cs (M = Co, Fe) in the absence of an external electrochemical driving force. Although conventional wisdom describes this thermocatalytic system using coupled electrochemical half-reactions, our kinetic studies reveal a contrasting mechanism at M-N-C surfaces crowded by HQ molecules, which are poised to stabilize the transition state via a unique inner-sphere mechanism. Molecular crowding of the surface changes the dominant reaction pathway and circumvents the rateâpotential relationship expected for electrocatalytic O2 reduction, opening new opportunities to design fuel cell systems that reduce O2 at lower overpotential by using mediators to drive thermocatalytic pathways.
In the second example,2 an approach to synthesize Fe-N-C is developed using inspiration from routes for the metalation of molecular macrocyclic complexes. FeNx moieties are formed without exposure to high temperatures (>200 °C) and their density is improved by increasing the availability of uncoordinated Nx binding sites in the N-doped carbon support. Aerobic HQ oxidation serves as a catalytic benchmark reaction to corroborate this improvement in Fe dispersion. I envision that the modularity of the synthetic approach will enable rational design of Fe-N-C catalysts through tailoring their underlying supports.
References
[1] Bates, J. S.; Biswas, S.; Suh, S.-E.; Johnson, M. R.; Mondal, B.; Root, T. W.; Stahl, S. S. J. Am. Chem. Soc. 2022, 144, 922â927.
[2] Bates, J. S.; Khamespanah, F.; Cullen, D. A.; Al-Zahrani, A.; Hopkins, M. N.; Martinez, J. J.; Root, T. W.; Stahl, S. S. Submitted.