6 research outputs found
Unique selectivity trends of highly permeable PAP[5] water channel membranes
Artificial water channels are a practical alternative to biological water channels for achieving exceptional water permeability and selectivity in a stable and scalable architecture. However, channel-based membrane fabrication faces critical barriers such as: (1) increasing pore density to achieve measurable gains in permeability while maintaining selectivity, and (2) scale-up to practical membrane sizes for applications. Recently, we proposed a technique to prepare channel-based membranes using peptide-appended pillar[5]arene (PAP[5]) artificial water channels, addressing the above challenges. These multi-layered PAP[5] membranes (ML-PAP[5]) showed significantly improved water permeability compared to commercial membranes with similar molecular weight cut-offs. However, due to the distinctive pore structure of water channels and the layer-by-layer architecture of the membrane, the separation behavior is unique and was still not fully understood. In this paper, two unique selectivity trends of ML-PAP[5] membranes are discussed from the perspectives of channel geometry, ion exclusion, and linear molecule transport. © 2018 The Royal Society of Chemistry.11Nsciescopu
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Carbon Corrosion in Polymer Electrolyte Fuel Cells: A Complex Interplay between Morphological Changes and Electrochemical Performance
A scalable membrane electrode assembly architecture for efficient electrochemical conversion of CO2 to formic acid
Abstract The electrochemical reduction of carbon dioxide to formic acid is a promising pathway to improve CO2 utilization and has potential applications as a hydrogen storage medium. In this work, a zero-gap membrane electrode assembly architecture is developed for the direct electrochemical synthesis of formic acid from carbon dioxide. The key technological advancement is a perforated cation exchange membrane, which, when utilized in a forward bias bipolar membrane configuration, allows formic acid generated at the membrane interface to exit through the anode flow field at concentrations up to 0.25 M. Having no additional interlayer components between the anode and cathode this concept is positioned to leverage currently available materials and stack designs ubiquitous in fuel cell and H2 electrolysis, enabling a more rapid transition to scale and commercialization. The perforated cation exchange membrane configuration can achieve >75% Faradaic efficiency to formic acid at <2 V and 300 mA/cm2 in a 25 cm2 cell. More critically, a 55-hour stability test at 200 mA/cm2 shows stable Faradaic efficiency and cell voltage. Technoeconomic analysis is utilized to illustrate a path towards achieving cost parity with current formic acid production methods
Elucidation of Critical Catalyst Layer Phenomena toward High Production Rates for the Electrochemical Conversion of CO to Ethylene
This work utilizes
EIS to elucidate the impact of catalyst–ionomer
interactions and cathode hydroxide ion transport resistance (RCL,OH–) on cell
voltage and product selectivity for the electrochemical conversion
of CO to ethylene. When using the same Cu catalyst and a Nafion ionomer,
varying ink dispersion and electrode deposition methods results in
a change of 2 orders of magnitude for RCL,OH– and ca. a 25% change in electrode
porosity. Decreasing RCL,OH– results in improved ethylene Faradaic efficiency (FE), up
to ∼57%, decrease in hydrogen FE, by ∼36%, and reduction
in cell voltage by up to 1 V at 700 mA/cm2. Through the
optimization of electrode fabrication conditions, we achieve a maximum
of 48% ethylene with >90% FE for non-hydrogen products in a 25
cm2 membrane electrode assembly at 700 mA/cm2 and
RCL,OH– is translated to other
material requirements, such as anode porosity. We find that the best
performing electrodes use ink dispersion and deposition techniques
that project well into roll-to-roll processes, demonstrating the scalability
of the optimized process