Guanxiong Wang

Cobalt-Based Coordination Polymer for Oxygen Reduction Reaction

Lack of control over the structure and electrically nonconductive properties of coordination polymers (CPs) creates a major hindrance to designing an active electrocatalyst for oxygen reduction reaction (ORR). Here, we report a new semiconductive and low-optical band gap CP structure [{Co3(μ3-OH)(BTB)2(BPE)2}{Co0.5N(C5H5)}], 1, that exhibits high-performance ORR in alkaline medium. The electrical conductivity of compound 1 was measured using impedance spectroscopy and found to be 5 × 10–4 S cm–1. The Ketjenblack EC-600JD carbon used as a support for all the electrochemical methods such as cyclic voltammetry, rotating disk electrode, rotating ring-disk electrode and Koutecký–Levich analysis. The as-synthesized Co-based catalyst has the ability to reduce O2 to H2O by a nearly four-electron process. The crystal structure of 1 shows that the trimeric unit {Co3(μ3-OH)(COO)5N3} and monomeric unit {Co(COO)2(NC5H4)2}2+ are linked with BTB and BPE linkers to form a three-dimensional structure. Theoretical calculations predict that the monomeric center acts as an active catalytic site for ORR. This could be due to the efficient overlap of highest occupied molecular orbital–lowest unoccupied molecular orbital between monomer and O2 molecule. This CP, 1, shows facile 3.6-electron ORR, and it is inexpensive compared with widely used Pt catalysts. Therefore, this CP can be used as a promising cathode material for fuel cells in terms of efficiency and cost effectiveness.