Chromophore amphiphile-polyelectrolyte hybrid hydrogels for photocatalytic hydrogen production

Hiroaki Sai, Aykut Erbas, Adam Dannenhoffer, Dongxu Huang, Adam Weingarten, Erica Siismets, Kyujin Jang, Karen Qu, Liam C. Palmer, Monica Olvera De La Cruz, Samuel I. Stupp*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

Hybrid systems based on covalent polymers and supramolecular assemblies offer unique opportunities for functional materials based on the pathway-dependent dynamic structures of supramolecular assemblies and the mechanical stability of covalent polymers. We report here on the synthesis of functional hybrid hydrogels containing self-assembling chromophore amphiphiles and polyelectrolytes. Chromophore amphiphiles were introduced into non-aqueous solvent swollen polymer matrices and self-assembly of the chromophore amphiphiles into crystalline nanostructures was triggered in the confined environment of the covalent network upon solvent exchange for water. Opposite charges in the covalent polyelectrolyte and the chromophore amphiphiles and sterics entrap the supramolecular assemblies within the mechanically stable network. However, molecular components necessary for catalysis, byproducts from photocatalysis, and the hydrogen produced are able to diffuse in or out of the covalent network to create a reusable robust host for photocatalysis. By varying the monomer and crosslinker composition in the feed, we can tune the porosity of the network as well as the chemical environment in which supramolecular crystallization of the chromophore amphiphiles takes place. This allows optimization of the hydrogel mechanical properties, retention of the chromophore amphiphile assemblies, and the photocatalytic reaction efficiency. Coarse-grained molecular dynamics simulations revealed that the chromophore amphiphile assembly is guided by the polyelectrolyte network via ionic interactions. We also demonstrate successful photocatalytic hydrogen production from catalyst-laden hybrid hydrogels with the turnover frequency approaching that of the supramolecular hydrogel system, and also show that the hybrid hydrogels can be reused over multiple cycles as photosensitizers.

Original languageEnglish (US)
Pages (from-to)158-168
Number of pages11
JournalJournal of Materials Chemistry A
Volume8
Issue number1
DOIs
StatePublished - Jan 7 2020

Funding

This work was primarily supported by the Center for Bio-Inspired Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under Award # DESC0000989. Molecular synthesis was supported by the National Science Foundation under NSF Award Number DMR-1121262. The authors thank the Sherman Fairchild Foundation for computational support. E. S. acknowledges the Materials Research Science and Engineering Center REU program, supported by the National Science Foundation under NSF Award Number DMR-1121262. The authors also thank Prof. Michael Wasielewski (Northwestern University) for access to the gas chromatography instrument, Zaida Alvarez-Pinto (North-western University) for assistance with optical imaging of the hydrogels, and Garrett Lau (Northwestern University) for assistance in acquiring thermogravimetric analysis data. This work made use of the following facilities at Northwestern University: the J. B. Cohen X-Ray Diffraction Facility, the EPIC facility (cryo-SEM), the Keck Biophysics facility (UV-Vis), the Biological Imaging Facility (CLSM), the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS) (X-ray scattering), and the IMSERC facility (TGA). The J. B. Cohen X-Ray Diffraction Facility is supported by the MRSEC program of the National Science Foundation (DMR-1121262) at the Materials Research Center of Northwestern University. The EPIC facility of the NUANCE Center has received support from the So and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. The Keck Biophysics facility has received support from a Cancer Center Support Grant (NCI CA060553). DND-CAT is supported by Northwestern University, E. I. DuPont de Nemours & Co., and The Dow Chemical Company. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. IMSERC facility has received support from the NSF (CHE-1048773); So and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the State of Illinois and International Institute for Nanotechnology (IIN).

ASJC Scopus subject areas

  • General Chemistry
  • Renewable Energy, Sustainability and the Environment
  • General Materials Science

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