Electron-Donors/Acceptors Interaction Enhancing Electrocatalytic Activity of Metal Organic Polymers for Oxygen Reduction.

Abstract

Catalysts with metal-Nx sites have long been considered as effective electrocatalysts for oxygen reduction reaction (ORR), yet the accurate structure-property correlations of these active sites remain debatable. Report here is a proof-of-concept method to construct 1,4,8,11-tetraaza[14]annulene (TAA)-based polymer nanocomposites with well-managed electronic microenvironment via electron-donors/acceptors interaction of altering electron-withdrawing β-site substituents. DFT calculation proves the optimal -Cl substituted catalyst (CoTAA-Cl@GR) tailored the key OH* intermediate interaction with Co-N4 sites under the d-orbital regulation, hence reaching the top of ORR performance with excellent turnover frequency (0.49 e s-1 site-1). The combination of in-situ scanning electrochemical microscopy and variable-frequency square wave voltammetry techniques contribute the great ORR kinetics of CoTAA-Cl@GR to the relatively high accessible site density (7.71×1019 site g-1) and fast electron outbound propagation mechanism. This work provides theoretical guidance for rational design of high-performance catalysts for ORR and beyond.