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  1. Free, publicly-accessible full text available July 11, 2022
  2. Free, publicly-accessible full text available July 1, 2022
  3. Carbon-based catalysts have been attracting extensive attention as viable candidates to replace platinum towards oxygen reduction reaction, a critical process at fuel cell cathode. An advancement has been the development of carbon-supported iron carbide (Fe3C/C) catalysts derived from the pyrolysis of metal organic frameworks (MOFs). In the present study, a series of Fe3C/C nanocomposites were prepared by controlled pyrolysis of FeMOF-NH2 with a systemic variation of the iron and zinc compositions in the MOF precursor. Scanning/transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopic measurements were carried out to examine the morphologies, structures, and elemental composition of the nanocomposites, whilemore »nitrogen adsorption/desorption and Raman studies were used to characterize the surface area and porosity. It was found that an optimal zinc to iron feeding ratio was required to produce a catalyst with a preferential pore size distribution. Electrochemical measurements revealed that the sample derived from 20% zinc replacement in the FeMOF-NH2 precursor exhibited the best electrocatalytic activity in alkaline media among the series, with the most positive onset potential and highest limiting current, which coincided with the highest surface area and porosity. The results suggest that deliberate structural engineering is critical in manipulating and optimizing the electrocatalytic activity of metal,nitrogen-codoped carbon nanocomposites.« less
  4. We advance a tripartite framework of language use to encompass language skills, the practice of language skills, and the subjective experiences associated with language use among Mexican-origin adolescents who function as language brokers by translating and interpreting for their English-limited parents. Using data collected over 2 waves from a sample of 604 adolescents (Wave 1: Mage = 12.41, SD = 0.97), this study identified 4 types of bilingual language broker profiles that capture the tripartite framework of language use: efficacious, moderate, ambivalent, and nonchalant. All 4 profiles emerged across waves and brokering recipients (i.e., mothers, fathers), except for Wave 1more »brokering for mother, in which case only 3 profiles (i.e., efficacious, moderate, and ambivalent) emerged. Three profiles emerged across time: stable efficacious, stable moderate, and other. The efficacious and stable efficacious profiles showed the most consistent relation to adolescents' academic competence. Improving bilingual language proficiency, together with fostering more frequently positive brokering experiences, may be an avenue to improving academic competence among Mexican-origin adolescents in the United States.« less