Physical Electronics and Surface Physics

Contains reports on two research projects.National Aeronautics and Space Administration (Grant NGR-22-009-091)M. I. T. Cabot Solar Energy FundJoint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E

Physical Electronics and Surface Physics

Contains research objectives and reports on two research projects.National Aeronautics and Space Administration (Grant NGR-22-009-091)M. I. T. Cabot Solar Energy FundJoint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E

Physical Electronics and Surface Physics

Contains research objectives, summary of research and reports on three research projects.National Aeronautics and Space Administration (Grant NGR-22-009-091)M.I.T. Cabot Solar Energy FundJoint Services Electronics Programs (U. S. Army, U.S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E

Physical Electronics and Surface Physics

Contains research objectives and reports on four research projects.National Aeronautics and Space Administration (Grant NGR-22-009-091)M. I. T. Cabot Solar Energy FundJoint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 36-039-AMC-03200(E

Physical Electronics and Surface Physics

Contains reports on three research projects.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 36-039-AMC-03200(E)National Aeronautics and Space Administration (Grant NGR-22-009-09-091)National Aeronautics and Space Administration (Grant NsG-496

Purification of Residual Ni and Co Hydroxides from Fe‐Free Alkaline Electrolyte for Electrocatalysis Studies

It is critical to control Fe impurity concentrations in oxygen-evolution-reaction electrocatalysis experiments so that unambiguous assignments of activity and mechanistic details can be made. An established method to prepare Fe-free KOH electrolyte is by using particulate Ni(OH)2 or Co(OH)2 as absorbents to remove the Fe from KOH or other neutral-to-alkaline electrolytes. However, this method yields residual Ni or Co species in the electrolyte which can be redeposited on the working electrode. Thus, current methods of Fe removal could convolute studies of OER. In this work, we compared two different methods, continuous electrolysis and nano-filtration, to remove the Ni and/or Co species from Fe-free alkaline electrolyte. We found the best approach is to pass the Fe-free electrolyte through a hydrophilic 0.1 μm polyethersulfone filter which decreases the Ni species concentration in 1 M KOH to single ppb levels. This result suggests the remaining Ni or Co species are primarily particulate in nature, consistent with their small solubility as ions. In comparison, extended pre-electrolysis of the electrolyte removed only a portion of the Ni/Co

Nanoscale semiconductor/catalyst interfaces in photoelectrochemistry

Semiconductor structures (for example, films, wires, particles) used in photoelectrochemical devices are often decorated with nanoparticles that catalyse fuel-forming reactions, including water oxidation, hydrogen evolution or carbon-dioxide reduction. For high performance, the catalyst nanoparticles must form charge-carrier-selective contacts with the underlying light-absorbing semiconductor, facilitating either hole or electron transfer while inhibiting collection of the opposite carrier. Despite the key role played by such selective contacts in photoelectrochemical energy conversion and storage, the underlying nanoscale interfaces are poorly understood because direct measurement of their properties is challenging, especially under operating conditions. Using an n-Si/Ni photoanode model system and potential-sensing atomic force microscopy, we measure interfacial electron-transfer processes and map the photovoltage generated during photoelectrochemical oxygen evolution at nanoscopic semiconductor/catalyst interfaces. We discover interfaces where the selectivity of low-Schottky-barrier n-Si/Ni contacts for holes is enhanced via a nanoscale size-dependent pinch-off effect produced when surrounding high-barrier regions develop during device operation. These results thus demonstrate (1) the ability to make nanoscale operando measurements of contact properties under practical photoelectrochemical conditions and (2) a design principle to control the flow of electrons and holes across semiconductor/catalyst junctions that is broadly relevant to different photoelectrochemical devices

Geographic and Sociodemographic Disparities in Drive Times to Joint Commission–Certified Primary Stroke Centers in North Carolina, South Carolina, and Georgia

Introduction: Timely access to facilities that provide acute stroke care is necessary to reduce disabilities and death from stroke. We examined geographic and sociodemographic disparities in drive times to Joint Commission–certified primary stroke centers (JCPSCs) and other hospitals with stroke care quality improvement initiatives in North Carolina, South Carolina, and Georgia. Methods: We defined boundaries for 30- and 60-minute drive-time areas to JCPSCs and other hospitals by using geographic information systems (GIS) mapping technology and calculated the proportions of the population living in these drive-time areas by sociodemographic characteristics. Age-adjusted county-level stroke death rates were overlaid onto the drive-time areas. Results: Approximately 55% of the population lived within a 30-minute drive time to a JCPSC; 77% lived within a 60-minute drive time. Disparities in percentage of the population within 30-minute drive times were found by race/ethnicity, education, income, and urban/rural status; the disparity was largest between urban areas (70% lived within 30-minute drive time) and rural areas (26%). The rural coastal plains had the largest concentration of counties with high stroke death rates and the fewest JCPSCs. Conclusion: Many areas in this tri-state region lack timely access to JCPSCs. Alternative strategies are needed to expand provision of quality acute stroke care in this region. GIS modeling is valuable for examining and strategically planning the distribution of hospitals providing acute stroke care