Abstract

Proton exchange membrane fuel cells (PEMFC) have attracted much attention in vehicles, portable electronics, and combined heat and power (CHP) systems, which are simple, efficient, clean, and pollution-free. O2 reduction reaction (ORR) that occurs on a fuel cell cathode exhibits sluggish kinetics and limits the turnover performances in corresponding devices. A hybrid bilayer membrane (HBM) electrochemical platform is a modular system to regulate the proton and electron pathways of ORR and control the product selectivity of ORR without altering the molecular structure of the HBM-embedded catalyst by using 1-dodecylboronic acid (DBA) as a transmembrane proton carrier.1 However, the catalytic active sites of HBMs for ORR are limited to two types of transitional metals—Cu and Fe ions.2 To go beyond this status quo, a new ligand framework, based on tris(2-pyridylmethyl)amine (TPA) and equipped with an alkylthiolate arm, suitable for coordinating a wide range of metal ions and capable of assembling into a self-assembled monolayer (SAM) in an HBM is synthesized, and the ORR product distributions on the HBMs incorporated with Ni, Co, Cu, and Fe are investigated. Lastly, the interplay between different metal ions is interrogated to discern their synergistic functions for ORR. This work broadens the range of catalytic metal centers that can be used in an HBM, thereby enabling HBM to act as a screening tool to search for dual-metal complexes with enhanced ORR activity and desirable selectivity for H2O.

Fig.1. Schematic of the HBM electrochemical platform utilized to regulate the dual-site metal catalytic activity in O2 reduction.

References:

1. 1. Gautam, R, et al.​ Angew. Chem. Int. Ed., 2018, 57, 13480-13483.

• Zeng, T., et al. ACS Catalysis, 2020, 10(21): 13149-13155.