Impact of Bubbles on Electrochemically Active Surface Area of Microtextured Gas-Evolving Electrodes.

The adverse effects of electrochemical bubbles on the performance of gas-evolving electrodes have been extensively studied. However, the ways in which bubbles dynamically alter the electrochemically active surface area during bubble evolution are not well understood. Here, we study hydrogen evolution at industrially relevant current densities by using controlled microtexture to examine this fundamental relationship. Surprisingly, the most densely microtextured electrodes have the lowest performance on an active surface area basis. Using high-speed imaging, we show that the benefits of microtexture to release smaller bubbles more consistently are outweighed by the inactivation induced by bubbles growing within the denser microtexture, causing these performance limitations. Additionally, we show that the area beneath adhered bubbles is electrochemically active, contrary to currently held assumptions. Our study therefore has broad implications for electrode design to avoid ineffective use of precious catalyst materials, which is especially critical for porous electrodes and three-dimensional structures with high specific surface areas.

Transient Effects Caused by Gas Depletion during Carbon Dioxide Electroreduction.

The novel use of carbon dioxide (CO2) electroreduction to generate carbon-based products which do not contribute to the greenhouse effect has promoted the vision of carbon dioxide as a renewable feedstock for future clean fuel production. Depending on the material choice for the electrocatalysis, a certain variety of products is expected from the carbon dioxide reduction reaction (CO2RR). However, as the CO2 concentration in areas close to the working electrode (relative to the diffusive boundary layer) decreases as it is being consumed and transformed into other products, the generation of H2 is favored to the detriment of CO2 electroreduction. Therefore, the extent to which H2 is produced can be used as a metric to evaluate the efficiency of CO2RR. This article proposes a model that accounts for the modes in which aqueous gas depletion evolves over time and affects the long-term CO2 electroreduction and the corresponding pH evolution near the electrode's surface. For the latter, two main contributions are distinguished: gas depletion due to CO2 consumption and ion generation in areas close to the electrocatalyst surface. pH is then suggested as an accurate and indirect means to measure CO2 concentration in a liquid electrolyte. We conclude that CO2 depletion causes a strong decay in the electrochemical reaction efficiency. In the end, we discuss several methods which may delay the onset of the adverse effects caused by gas depletion, such as the utilization of pulsed electroreduction, cycling the applied current to electrodes on and off periodically.

Designing a Liver Transplant Patient and Family Decision Support Tool for Organ Offer Decisions.

BACKGROUND: For liver transplant candidates on the waiting list, deciding to accept a donor organ with known or potential risk factors can be stressful and can lead to declined offers. Current education for patients and family often takes place during transplant evaluations and can be overwhelming and result in low retention and poor understanding of donor quality. METHODS: In the first phase, we sought to understand provider experiences when counseling patients about donor risks and donor offers. We conducted interviews and focus groups with liver transplant providers at 1 local center and at a national clinician conference. Twenty providers participated: 15 hepatologists and 5 surgeons. The provider feedback was used to create an initial outline of content that is consistent with decision support frameworks. In a second phase, graphic design collaborators created mockups of a patient-friendly tool. We reviewed mockups with 4 transplant coordinators and 9 liver transplant candidates for feedback on clarity and utility to prepare for an organ offer. Patient responses allowed a comparison of perceived readiness to receive an offer call before and after viewing mockups. RESULTS: We identified themes relating to the offer process, repetition and timing of education, and standardization and tailoring of content. The results indicated a gap in available education after the evaluation session, and information specific to offer decisions is needed. Patient feedback emphasized the need to review the offer process before a real offer. CONCLUSIONS: Patients and providers responded favorably to a patient tool addressing existing gaps in education while waiting for a donor offer. Additional patient, family, and provider feedback will guide the development of an interactive tool to prepare patients and families for an offer decision.

Tool to Aid Patients in Selecting a Liver Transplant Center.

Variations in candidate and donor acceptance criteria may influence access and mortality for liver transplantation. We sought to understand how recipient and donor characteristics vary across centers and how patients interpret this information, and we used these data to develop a tool to provide tailored information to candidates seeking a center (www.transplantcentersearch.org). We analyzed liver recipient data from the Scientific Registry of Transplant Recipients to determine how recipient and donor characteristics (eg, age, Medicaid use, and human immunodeficiency virus status) varied across programs. Data included recipients and donors at each US program between January 1, 2015, and December 31, 2017. The variation in characteristics was plotted with centers stratified by total transplant volume and by volume of each characteristic. A subset of characteristics was plotted to show variation over 3 years. We created mockups of potential reports displaying recipient characteristics alongside pretransplant and posttransplant outcomes and solicited feedback at patient and family interviews and focus groups, which included 39 individuals: 10 pilot interviews with candidates seeking liver transplant at the University of Minnesota-Fairview (UMNF) and 5 focus groups with 13 UMNF candidates, 6 UMNF family members, and 10 national recipients. Transcripts were analyzed using a thematic analysis. Several themes emerged: (1) Candidates experience gaps in existing education about center options; (2) patients requested information about how selection criteria might impact access to transplant; and (3) information tailored to a candidate's medical characteristics can inform decisions. Characteristics shown on mockups varied across centers (P < 0.01). Variation was widespread for small and large centers. In conclusion, variation exists in recipient and donor characteristics across centers. Liver transplant patients provide positive feedback upon viewing patient-specific search tools.

Comparing Pretransplant and Posttransplant Outcomes When Choosing a Transplant Center: Focus Groups and a Randomized Survey.

BACKGROUND: In response to calls for an increased focus on pretransplant outcomes and other patient-centered metrics in public reports of center outcomes, a mixed methods study evaluated how the content and presentation style of new information influences decision-making. The mixed methods design utilized qualitative and quantitative phases where the strengths of one method help address limitations of the other, and multiple methods facilitate comparing results. METHODS: First, a series of organ-specific focus groups of kidney, liver, heart, and lung patients helped to develop and refine potential displays of center outcomes and understand patient perceptions. A subsequent randomized survey included adult internet users who viewed a single, randomly-selected variation of 6 potential online information displays. Multinomial regression evaluated the effects of graphical presentations of information on decision-making. RESULTS: One hundred twenty-seven candidates and recipients joined 23 focus groups. Survey responses were analyzed from 975 adults. Qualitative feedback identified patient perceptions of uncertainty in outcome metrics, in particular pretransplant metrics, and suggested a need for clear guidance to interpret the most important metric for organ-specific patient mortality. In the randomized survey, only respondents who viewed a note indicating that transplant rate had the largest impact on survival chose the hospital with the best transplant rate over the hospital with the best posttransplant outcomes (marginal relative risk and 95% confidence interval, 1.161.501.95). CONCLUSIONS: The presentation of public reports influenced decision-making behavior. The combination of qualitative and quantitative research helped to guide and enhance understanding of the impacts of proposed changes in reported metrics.