Construction of cobalt nanoparticles decorated intertwined N-doped carbon nanotube clusters with dual active sites for highly effective 4-nitrophenol reduction

Abstract

Fabricating catalysts with dual active sites is an effective approach for boosting the catalytic activities. In this work, a highly active catalyst with Co nanoparticles decorating on interconnected N-doped carbon nanotube clusters (Co@NCNTS) was synthesized by directly heating the ZIF-67 precursor in H2/Ar atmosphere. The Co nanoparticles exhibited small particle sizes (7–11 nm) and high dispersions, which will prevent the particles from coalescence and agglomeration. In addition, the intertwined NCNTS network could also provide a long-term conductivity, which will facilitate the transfer of charge carriers and effectively enhance the catalytic performance. After that, the catalytic reduction performance of the catalysts to 4-nitrophenol in the presence of NaBH4 solution was also investigated. As expected, the as-synthesized Co@NCNTS catalyst exhibited a superior catalytic reduction ability to 4-nitrophenol in the presence of NaBH4 solution with an almost 100% conversion ratio and a high apparent kinetic rate constant k of 0.37 min−1. Furthermore, the pristine NCNTS also exhibited well catalytic reduction performance to 4-nitrophenol with a k constant of 0.09. The synergetic effect between Co nanoparticles and NCNTS could effectively boost the catalytic reduction performance. Thus, the excellent catalytic performance could own to the confinement effect of ZIF-67 precursors, high conductivity and synergetic effect between Co nanoparticles and NCNTS.