Co-electrolysis of water and CO2 to produce hydrogen and CO would provide an alternative pathway to making chemicals and fuels. The process could provide a way to use excess renewable electricity, or could be coupled to nuclear or carbon-based power generation. Opus 12 has overcome barriers to using a proton exchange membrane (PEM) reactor for this reaction by modifying the cathode catalyst layer to enhance simultaneous electrochemical H2 production and CO2 reduction. Current reactor performance metrics in terms of selectivity, current density, and applied voltage meet or exceed internal targets. However, the cell lifetime must be extended for a commercial product to be feasible. Through this H2@Scale project, we propose to work with the Weber Group at LBNL to diagnose performance decay mechanisms that currently limit the lifetime of the electrochemical syngas generator. LBNL is host to a number of advanced PEM diagnostic tools and lab scientists have unique experience in exploring performance and lifetime tradeoffs at the component to cell scales. Using the results of this study, the identified limiting mechanisms will be mitigated through improved cell and catalyst design.

The Parties developed understanding of water and thermal management in fuel cells using a detailed 1-D model for the through-plane direction, a gas-channel relation model for the flow-channel direction, and a method to account for the rib/channel direction. The model simulates and predicts the water transport phenomena occurring within the fuel-cell sandwich, including the complex interplay among the various phases. This model enables optimum designs, operating conditions, and material properties for use in commercial PEFCs for automotive applications. In addition, novel advanced diagnostic methods and submodels were developed to determine the critical properties and model parameters and explore specific phenomena (e.g., ionomer thin films).

Rationale : Methamphetamine (MA) dependence frequently co- occurs with HIV infection and increases the likelihood of poorer outcomes, including neurocognitive impairment. One aspect of cognition affected in both HIV and MA and may be a target for intervention is prospective memory (PM), or remembering to perform an intended action at a specific time. Self-generation is a potentially powerful approach to improve PM, hypothetically by supporting strategic aspects of encoding and cue monitoring that underlie PM impairment in HIV/MA individuals. This dissertation project sought to: 1) evaluate the efficacy of self- generation on PM in HIV/MA adults on basic, clinical, and naturalistic PM paradigms; 2) determine neurocognitive mechanisms of self-generation on PM in HIV/MA; and 3) explore potential correlates of self-generation on PM in HIV/MA. Design : Using a 3-group design (N=83), this study examined the effectiveness of self-generation in HIV+MA- and HIV+MA+ individuals compared to healthy comparison individuals (HIV-MA-) across three PM tasks of varying ecological validity. Participants were also administered a structured psychiatric interview, neuropsychological battery, and neuromedical examination. Results : Across tasks utilizing within-subjects designs (basic, clinical PM tasks), participants were more likely to respond to the PM cue at recall and recognition for self-generated cues relative to didactically-learned cues (ps<0.05; Hedge's gs=0.28-0.53); group and interaction factors were non- significant (ps>0.05). On the basic PM task, participants responded more quickly to the ongoing lexical decision- making task during the self-generated PM trials relative to the didactic trials (p=0.033; Hedge's g=0.18). Neurocognitively-impaired HIV+ participants experienced greater benefit from self-generation on the basic PM task relative to their neurocognitively-normal counterparts (p=0.008; Hedge's g difference=0.42). No main or interaction effects were observed on the naturalistic PM task, but longitudinal analyses revealed a trend-level effect of self-generation in the combined clinical sample. Across all tasks, no neurocognitive, psychiatric, HIV disease, or MA use characteristics were associated with self-generation benefit. Relevance : This study establishes potential effectiveness of self-generation to improve PM in healthy and HIV-infected adults, yielding effects in the small-to-medium range. Future research should seek to expand test mechanisms to health-related behaviors as well as the utility of a combined approach with manipulations designed to enhance PM cue monitoring

A macroscopic-modeling methodology to account for the chemical and structural properties of fuel-cell diffusion media is developed. A previous model is updated to include for the first time the use of experimentally measured capillary pressure -- saturation relationships through the introduction of a Gaussian contact-angle distribution into the property equations. The updated model is used to simulate various limiting-case scenarios of water and gas transport in fuel-cell diffusion media. Analysis of these results demonstrate that interfacial conditions are more important than bulk transport in these layers, where the associated mass-transfer resistance is the result of higher capillary pressures at the boundaries and the steepness of the capillary pressure -- saturation relationship. The model is also used to examine the impact of a microporous layer, showing that it dominates the response of the overall diffusion medium. In addition, its primary mass-transfer-related effect is suggested to be limiting the water-injection sites into the more porous gas-diffusion layer.