Advances in metal-cation-free, quaternary ammonium, polymer alkaline anion exchange membranes (AAEMs) have provided a recent resurgence of interest in the alkaline fuel cell (AFC). The alkaline environment supported by the AAEM offers several potential advantages, including opportunities for the use of non-noble metal catalysts with high energy density and logistically favorable fuels and oxidants, such as methanol and air. However, recent experimental literature has shown that the AAEM derived AFCs have considerable resistive losses that can be attributed to the AAEM. This work describes a dusty fluid model used to predict AAEM conductivities as a function of relative humidity and membrane properties in an initial attempt at forming a framework for understanding the processes at work. A percolation model is used to account for the membrane structure. The model is validated using Nafion 115 conductivity data.

A high-resolution, nondestructive X-ray computed tomography ͑XCT͒ technique is applied to image the three-dimensional ͑3D͒ microstructure of a solid oxide fuel cell ͑SOFC͒ composed of a solid yttria-stabilized zirconia ͑YSZ͒ electrolyte and a porous nickel YSZ ͑Ni-YSZ͒ anode. The X-ray microscope uses the 8 keV Cu K␣ line from a laboratory X-ray source, with a reflective condenser optic lens providing a spatial resolution of 42.7 nm. The reconstructed volume data is visualized as 3D images and further postprocessed in binary-image format to obtain structural parameters. The porosity is calculated using a voxel counting method, and tortuosity is evaluated by solving the Laplace equation. A 3D representation of the microstructure is used to calculate true structural parameters and carry out a detailed study of the gas transport within an SOFC electrode at the pore scale. Simulation of multicomponent mass transport and electrochemical reactions in the anode microstructure using the XCT data as geometric input illustrate the impact of this technique on SOFC modeling.

Present solid oxide fuel cells (SOFCs) use complex materials to provide (i) sufficient stability and support, (ii) electronic, ionic, and mass transport, and (iii) electrocatalytic activity. However, there is a limited quantitative understanding of the effect of the SOFC's three dimensional (3D) nano/microstructure on electronic, ionic, and mass-transfer-related losses. Here, a nondestructive tomographic imaging technique at 38.5 nm spatial resolution is used along with numerical models to examine the phase and pore networks within an SOFC anode and to provide insight into the heterogeneous microstructure’s contributions to the origins of transport-related losses. The microstructure produces substantial localized structure-induced losses, with approximately 50% of those losses arising from phase cross-sectional diameters of 0.2μm or less.

Photocatalytic assembly of heterometallic nanoarchitectures via plasmonic hot electrons is demonstrated by liquid-phase, reductive photodeposition of platinum (Pt) onto gold nanorods (AuNR) under longitudinal surface plasmon (LSP) excitation. Nucleation of Pt 0 from PtCl 6 2−was initiated by plasmonic hot electrons at the Au surface. Sub-5 nm epitaxial overgrowth of Pt followed a core−shell morphology. Measured 6.5 longitudinal:transversal growth aspect ratio revealed longitudinal growth preferentiality that was consistent with the LSP dipole polarity. In situ spectroscopic monitoring of the photocatalytic growth process permitted real-time feedback into Au surface functionalization with PtCl 6 2− according to 16 nm red-shift in its Cl−Pt ligand-to-metal charge-transfer (L π MCT) band involving ligand π orbitals. Subsequent Pt 0 growth kinetics were tracked using the L π MCT band. Discrete dipole models elucidated evolving lightmatter interactions of Pt-decorated AuNR that were consistent with experimental characterization. These studies provide a foundational mechanistic understanding toward guided assembly of heterometallic nanoarchitectures at ambient conditions via plasmonic hot electrons.

The combination of cation exchange membrane (CEM) and anion exchange membrane (AEM) electrolytes to form of a hybrid, or bipolar membrane (BPM) electrolyte, can have unique advantages for electrochemical systems including fuel cells, electrolyzers, electrodialysis, and photovoltaic solar-to-fuel devices. However, a major challenge for this approach is the development of a stable and active interfacial region (i.e., junction) that adjoins the CEM and AEM layers. Moreover, a fundamental understanding of transport at the CEM-AEM junction is lacking. Therefore, the present study focuses on the theoretical development and analysis of the nature of the BPM interface. A Poisson-Nernst-Planck (PNP) theory is formalized and applied to a representative BPM interface. The findings are reported in terms of bias (i.e., overpotential) in a galvanic device with respect to CEM and AEM material requirements. Specific attention is paid to our interests in the application of the BPM to a fuel cell device with an acidic (CEM) anode and alkaline (AEM) cathode. We demonstrate that a BPM with an acidic CEM anode and alkaline AEM cathode must promote a trap-assisted type of recombination mechanism under forward bias. Without such a mechanism, large overpotentials are needed to drive ionic recombination processes. Low temperature fuel cells have had difficulty in reaching the mass market despite promise as an efficient and scalable power source. Issues associated with costs, reliability, and ease of integration have made it difficult to disrupt established energy storage and conversion technologies. Fuel cell costs are often driven by the use of noble metal catalysts and fluorinated polymeric electrolytes.1 Numerous research groups explore catalyst materials in search of methods to remove platinum (Pt) and other precious metal electrocatalysts from low temperature fuel cell systems. To their credit, Pt content in polymer electrolyte membrane hydrogen/air fuel cells have dropped from upwards of 5 mg/cm 2 in the 1980s to approximately 0.125-0.3 mg/cm 2 at present. 1,2Other portions of the research community have turned their attention from acidic polymer electrolytes, a type form of cation exchange membrane (CEM), to alkaline anion exchange membrane (AEM) materials. While less mature, AEM materials have been steadily improving with notable improvements in metrics such as conductivity and stability. 3-6The motivation for the move to AEM materials is the recognition that oxygen reduction reaction (ORR) can be performed without Pt-based electrocatalysts. However, the hydrogen and methanol oxidation reaction at an alkaline ionomer-catalyst interface can also experience a voltage penalty associated with specific adsorption of cationic groups and/or other intermediates. [7][8][9] In addition to challenges with catalysts, a fuel cell system's balance of plant (BoP) can turn a simple device into a complex system. The BoP, which is typically comprised of radiators or heat exchangers, humidifiers, flow regulators, and power conditioning components,...