WashU affiliated authors: Sung Beom Cho, Rohan Mishra (Dept. of Mechanical Engineering and Materials Science), Cheng He, Shrihari Sankarasubramanian, Javier Parrondo, Jing Xie, Vijay Ramani (Dept. of Energy, Environmental, and Chemical Engineering), Arashdeep Singh Thind (Institute of Materials Science and Engineering)
Abstract: Clusters of nitrogen- and carbon-coordinated transition metals dispersed in a carbon matrix (e. g., Fe−N−C) have emerged as an inexpensive class of electrocatalysts for the oxygen reduction reaction (ORR). Here, it was shown that optimizing the interaction between the nitrogen-coordinated transition metal clusters embedded in a more stable and corrosion-resistant carbide matrix yielded an ORR electrocatalyst with enhanced activity and stability compared to Fe−N−C catalysts. Utilizing first-principles calculations, an electrostatics-based descriptor of catalytic activity was identified, and nitrogen-coordinated iron (FeN4) clusters embedded in a TiC matrix were predicted to be an efficient platinum-group metal (PGM)-free ORR electrocatalyst. Guided by theory, selected catalyst formulations were synthesized, and it was demonstrated that the experimentally observed trends in activity fell exactly in line with the descriptor-derived theoretical predictions. The Fe−N−TiC catalyst exhibited enhanced activity (20 %) and durability (3.5-fold improvement) compared to a traditional Fe−N−C catalyst. It was posited that the electrostatics-based descriptor provides a powerful platform for the design of active and stable PGM-free electrocatalysts and heterogenous single-atom catalysts for other electrochemical reactions.