Two-dimensional iron–tetracyanoquinodimethane (Fe–TCNQ) monolayer: an efficient electrocatalyst for the oxygen reduction reaction

Abstract

Searching for efficient, cheap, and stable non-Pt electrocatalysts for the oxygen reduction reaction (ORR) has been a major challenge for the development of fuel cells. Herein, we systematically investigated the potential of the experimentally synthesized two-dimensional (2D) metal–tetracyanoquinodimethane (M–TCNQ, where M denotes Mn, Fe, and Co) monolayers as novel ORR catalysts by means of density functional theory (DFT) computations. Our results revealed that O₂ molecules can be chemisorbed and efficiently activated on the M–TCNQ monolayers, and the subsequent oxygen reduction can readily proceed via a 4e⁻ pathway. Among the monolayers, the Fe–TCNQ monolayer exhibits the highest catalytic activity with onset potentials of 0.63 and −0.20 V in acidic and alkaline media, respectively. Remarkably, its electrocatalytic performance could be further enhanced by the attachment of axial halogen ligands. Therefore, the Fe–TCNQ monolayer might serve as a promising alternative to Pt-based catalysts for the ORR in fuel cells.