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  1. Atomically dispersed and nitrogen-coordinated single Ni sites ( i.e. , NiN x moieties) embedded in partially graphitized carbon have emerged as effective catalysts for CO 2 electroreduction to CO. However, much mystery remains behind the extrinsic and intrinsic factors that govern the overall catalytic CO 2 electrolysis performance. Here, we designed a high-performance single Ni site catalyst through elucidating the structural evolution of NiN x sites during thermal activation and other critical external factors ( e.g. , carbon particle sizes and Ni content) by using Ni–N–C model catalysts derived from nitrogen-doped carbon carbonized from a zeolitic imidazolate framework (ZIF)-8. The N coordination, metal–N bond length, and thermal wrinkling of carbon planes in Ni–N–C catalysts significantly depend on thermal temperatures. Density functional theory (DFT) calculations reveal that the shortening Ni–N bonds in compressively strained NiN 4 sites could intrinsically enhance the CO 2 RR activity and selectivity of the Ni–N–C catalyst. Notably, the NiN 3 active sites with optimal local structures formed at higher temperatures ( e.g. , 1200 °C) are intrinsically more active and CO selective than NiN 4 , providing a new opportunity to design a highly active catalyst via populating NiN 3 sites with increased density. We alsomore »studied how morphological factors such as the carbon host particle size and Ni loading alter the final catalyst structure and performance. The implementation of this catalyst in an industrial flow-cell electrolyzer demonstrated an impressive performance for CO generation, achieving a current density of CO up to 726 mA cm −2 with faradaic efficiency of CO above 90%, representing one of the best catalysts for CO 2 reduction to CO.« less
    Free, publicly-accessible full text available May 18, 2023
  2. Free, publicly-accessible full text available April 26, 2023
  3. Recently, graphene fibers derived from wet-spinning of graphene oxide (GO) dispersions have emerged as viable electrodes for fiber-shaped supercapacitors (FSCs) and/or batteries, wherein large surface area, high electrical conductivity, and sufficient mechanical strength/toughness are desired. However, for most fiber electrodes reported so far, compromises have to be made between energy-storage capacity and mechanical/electrical performance, whereas a graphene fiber with high capacity and sufficient toughness for direct machine weaving or knitting is yet to be developed. Inspired by the alum mordant used for natural dyes in the traditional textile dyeing industry, our research group has synthesized wet-spun GO fibers and coagulated them with different multivalent cations ( e.g. Ca 2+ , Fe 3+ , and Al 3+ ), where dramatically different fiber morphologies and properties have been observed. The first principles density functional theory has been further employed to explain the observed disparities via cation–GO binding energy calculation. When assembled into solid-state FSCs, Al 3+ -based reduced GO (rGO) fibers offer excellent stability against bending, and a specific capacitance of 148.5 mF cm −2 at 40 mV s −1 , 1.4, 4.8, and 6.8 times higher than that of the rGO fibers based on other three coagulation systems (Fe 3+ ,more »Ca 2+ and acetic acid), respectively. The volumetric energy density of the Al 3+ -based FSC is up to 13.26 mW h cm −3 , while a high power density of 250.87 mW cm −3 is maintained.« less