Chinese scholars have made new progress in the field of fuel cells

Figure Schematic diagram of Pt/C@COF-Nafion™ catalytic layer and its mechanism of action in fuel cells

With the support of the National Natural Science Foundation of China (approval numbers: 22171022, 21922502, 21971017, 21805292, 21625102), the team of Professor Wang Bo and Professor Feng Xiao from the School of Chemistry and Chemical Engineering of Beijing Institute of Technology have made new progress in the field of fuel cells, and the relevant research results are based on "Covalent organic framework-based high-performance fuel cells based on covalent organic framework porous ionomers.
" porous ionomers for high-performance fuel cells", published in the journal
Science on October 14, 2022.
Links to papers: _istranslated="1">.

Proton exchange membrane fuel cells are one of the most promising hydrogen energy utilization methods, and the key to their technological development and large-scale application lies in the development of high-performance, low-cost membrane electrode materials
.
The catalytic layer, composed of Pt/C catalysts and ionomers, serves as the core of the membrane electrode and is the site
of electrochemical reactions in fuel cells.
In order to ensure the efficiency of the electrochemical reaction, the catalytic layer needs to provide a channel
for the protons and reaction gases required for the reaction to reach the surface of the catalyst at the same time.
At present, the ionomer used in the catalytic layer is a chain perfluorosulfonic acid resin (PFSA, Nafion), which can achieve rapid conduction
of protons.
At the same time, however, Nafionon over-wraps the catalyst, reducing the utilization of the active site of the catalyst and causing greater gas resistance
.

In view of this challenge, a porous covalent organic framework (COF) ionomer suitable for the catalytic layer of fuel cells is proposed and constructed, which improves the mass transfer problem in the gas-solid-liquid three-phase interface, breaks through the constraints of traditional chain ionomers, significantly improves the mass transfer efficiency of the catalytic layer, and greatly improves the power density
of fuel cells.
As shown, the two-dimensional polymer planar structure is formed by an infinitely periodic extension of a hexagonal skeleton in a two-dimensional direction, with a sulfonic acid group cantilever anchored inside the hexagonal skeleton providing high proton conduction capacity, and COF channels providing pathways for oxygen and water
.
The use of porous COF ionomers increased the mass activity of commercial Pt/C catalysts and the peak power density of fuel cells by 1.
6 times
.

Porous ionomers introduce rigid development framework nanosheets with rich mesopores without sacrificing proton conductivity, optimize the ORR three-phase microenvironment of the fuel cell catalytic layer, and greatly improve the performance of
fuel cells.
COF has good thermal stability, acid-base stability, swelling resistance and structural designability, which makes it have broad application prospects
in high-temperature fuel cells or alkaline fuel cells.