Edge-enriched Ni-N4 atomic sites embedded enoki-mushroom-like carbon nanotubes assembling hollow fibers for CO2 conversion and flexible Zn-air battery

Explorations of multifunctional catalysts for electrochemical reactions, such as oxygen electrocatalysis and CO2 electroreduction, are key issues for energy crisis and global warming. Herein, the hollow fiber stitched by enoki-mushroom-like carbon nanotube with enriched Ni-N4 single-atomic edge-sites (Ni/N-ESC) is constructed. The nickel clusters are introduced to catalyze in-situ growth of carbon nanotubes and preferentially anchor single-atomic Ni-N sites. These hairy units stitch together similar to enoki-mushroom and constitute the highly porous matrix for hollow fibers. After self-sacrifice of nickel clusters, hollow fibers assembled by carbon nanotubes with edge-enriched single-atomic Ni-N4 sites are constructed. Both theoretical and experimental results demonstrate the edge-rich single-atomic sites manifest superior activities on both oxygen and CO2 catalysis. Meanwhile, the highly porous and conductive framework favors the fast kinetics and gives abundant active sites. Taking above advantages, the Ni/N-ESC hollow fiber manifests the outstanding activities towards both oxygen catalysis and CO2 conversions. Moreover, the flexible Zn-air battery assembled with Ni/N-ESC hollow fiber delivers the good flexibility, high power/energy density and stable property during long-term cycling at both ambient (25 °C) and freezing (-20 °C) temperatures. Therefore, this work not only provides a new platform to design high efficient catalysts for multifarious electrochemical reactions, but also promotes the development of flexible Zn-air battery working in broadened temperature range.