Bicontiunous Janus Materials

Abstract

Hydrogen fuel cells can contribute to the transition to a more sustainable global society. Hydrogen and oxygen are used for the conversion of chemical energy to electrical energy, with water as a waste product. There is a limiting factor however to the power density output of these cells. At high humidity water condenses inside the pores of the gas diffusion layer (GDL), reducing the oxygen uptake of the cell. GDLs with patterned wettability can mitigate this problem. We propose the use of a porous Janus material, with asymmetric surface properties as GDL to provide separate pathways for the diffusion of oxygen and the removal of water from the cell. Bicontinuous interfacially jammed emulsion gels (bijels) are used as precursor for such a material. Bijels have a unique morphology with interpenetrating oil and water channels separated by a layer of nanoparticles. By selective hydrophobization of the nanoparticle scaffold inside a bijel, a Janus material can be obtained. The surface modification is done using alkyl silanes, more specific octadecyl trichlorosilane. Different reaction times and concentrations are studied to obtain the optimal effect. With Scanning Electron Microscopy (SEM) and Scanning Laser Confocal Microscopy the modified bijels are characterized, where Reconstitution experiments are executed to monitor the wetting behavior of hydrophobic and hydrophilic liquids inside the pores of the treated bijel scaffold.