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Iron-based anode materials, such as Fe2O3 and FeSe2 have attracted widespread attention for lithium-ion batteries due to their high capacities. However, the capacity decays seriously because of poor conductivity and severe volume expansion. Designing nanostructures combined with carbon are effective means to improve cycling stability. In this work, ultra-small Fe2O3 nanoparticles loaded on a carbon framework were synthesized through a one-step thermal decomposition of the commercial C15H21FeO6 [Iron (III) acetylacetonate], which could be served as the source of Fe, O, and C. As an anode material, the Fe2O3@C anode delivers a specific capacity of 747.8 mAh g−1 after 200 cycles at 200 mA g−1 and 577.8 mAh g−1 after 365 cycles at 500 mA g−1. When selenium powder was introduced into the reaction system, the FeSe2 nano-rods encapsulated in the carbon shell were obtained, which also displayed a relatively good performance in lithium storage capacity (852 mAh g−1 after 150 cycles under the current density of 100 mA·g−1). This study may provide an alternative way to prepare other carbon-composited metal compounds, such as FeNx@C, FePx@C, and FeSx@C, and found their applications in the field of electrochemistry. [ABSTRACT FROM AUTHOR]

Groundwater resources are playing an increasingly vital role in water supply for domestic and irrigation purposes in the Yinchuan Plain, along with the reduction in water transfer from the Yellow River. This study aimed to identify the current status of phreatic water quality and associated hydrogeochemical processes in an irrigated region along the upper Yellow River. A total of 78 water samples were collected in September 2018 for chemical analysis. Results showed that the phreatic water was excellent or good in most areas west of the Yellow River, while it was poor or very poor quality in some places east of the Yellow River. The nitrate contamination is particularly severe in the pluvial-alluvial plain, relating to the localized fine-grained zone with low permeability. Most samples had no sodium hazard but had magnesium hazard. Additionally, the overall evolutionary trend of the phreatic water showed the transformation of Ca-Mg-HCO3 into Na-Cl-SO4 type. Rock weathering and evaporation jointly predominate the evolution of phreatic water chemistry. The main geochemical processes involve the dissolution/precipitation of gypsum, halite, dolomite. and calcite, along with the cation exchange. Insights from this work have important implications for groundwater sustainable management in such irrigated regions along the upper Yellow River. [ABSTRACT FROM AUTHOR]