# Design and Characterization of Hybrid Multilayer Structures: Layer-by-Layer Growth of Polymer and Graphene Oxide Assemblies and Their Utility in Fuel Cell Applications

## TL;DR

Scientists created hybrid layers of polymer and graphene oxide that reduce hydrogen gas leakage in fuel cells.

## Contribution

A new method for layer-by-layer assembly of sulfamate-modified polymer and sulfate-modified graphene oxide for fuel cell applications.

## Key findings

- Hybrid multilayer structures reduced H2 gas crossover by 15% in PEM fuel cells.
- Layer thickness was only 12 nm while maintaining structural consistency with calculations.
- XPS confirmed Zr/S stoichiometry in the assembled multilayer structures.

## Abstract

We report the layer-by-layer growth of poly­(ethylenimine)
(PEI)
that has been modified with sulfamate functionalities (S-PEI) using
Zr4+-complexation interlayer linking chemistry. We have
also deposited adlayers of graphene oxide (GO) that have been modified
to possess sulfate functionalities (S-GO), onto the S-PEI layers.
The multilayer assemblies are formed with sulfamate/sulfate and sulfate/sulfate
(S-PEI + S-GO) interlayer linking chemistry. In all cases the adlayer
thickness is consistent with predictions based on van der Waals volume
and/or molecular mechanics calculations. X-ray photoelectron spectroscopy
(XPS) is used to characterize the Zr/S stoichiometry in the multilayer
assembly. The utility of these hybrid multilayer structures is demonstrated
in a Proton Exchange Membrane (PEM) fuel cell, where they are shown
to reduce H2 gas crossover by 15% with only a 12 nm thick
layer.