Synthesis of distorted octahedral C-doped nickel nanocrystals encapsulated in CNTs: A highly active and stable catalyst for water pollutions treatment

A distorted octahedral C-doped nickel nanocrystals (DOCNs) encapsulated in carbon nanotubes (CNTs) was synthesized and used as the efficient catalyst for pollutants treatment. The characterizations and density func-tional theory calculations proved that high amount of dissolved carbon in DOCNs is responsible for the distorted octahedral structure, which enhances the adsorption of the HCOOH and Cr(2)O(7)(2- )and reduces the activation energy barrier of HCOOH to produce active hydrogen comparing with the metallic Ni. The reaction rate constants of DOCN-550 (k = 1.38 min(-1)), DOCN-650 (k = 0.418 min-1) and DOCN-750 (k = 0.207 min-1) were higher than those of nickel foam (k = 0.012 min(-1)), Ni/CNTs (k = 0.087 min(-2)) and commercial Pd/C (k = 0.158 min-1). Moreover, DOCN-550 showed good reusability and the activity of DOCN-550@NF can maintain more than 500 h at high weight hourly space velocity (WHSV) and Cr(6+ )concentration. And DOCN-550 can also be applied for reducing other organic pollutants in water. This study provides a highly active and stable catalyst for the degradation of toxic hexavalent chromium and other organic pollutants in water.