Effective Catalytic Reduction of 4-Nitrophenol to 4-Aminophenol over Etched Halloysite Nanotubes@α-Ni(OH)2

A series of supported alpha-Ni(OH)(2) structures on etched halloysite nanotubes (eHAs) are synthesized via a one-pot facile co-precipitation method. By expediently controlling the variety of alkali source, etched halloysite nanotubes@alpha-Ni(OH)(2) (eHA@alpha-Ni(OH)(2)) with different alpha-Ni(OH)(2) morphologies and Ni2+-ion contents can be achieved. The prepared eHA@alpha Ni(OH)(2) is used to catalytically reduce 4-nitrophenol (4-NP). It shows that eHA@alpha-Ni(OH)(2) prepared with n-butylamine as an alkali source (eHA@alpha-Ni(OH)(2)-B) exhibits a higher k(app) of 1.458 x 10(-2) s(-1) and K of 583.27 s(-1).g(-1). The catalytic reduction property is in accordance with the Ni2+-ion content of eHA@aNi(OH)(2). Moreover, it also exhibits a good cycle stability due to the synergy of the support eHA and the supported Ni2+ ions in alpha Ni(OH)(2), which can achieve a 99% 4-nitrophenol conversion after 11 cycles. The Ni2+-ion reduction experiment illustrates that the Ni2+ ion is the activation site and the enhanced 4-NP reduction activity of eHA@alpha-Ni(OH)(2)-B is attributed to the higher Ni2+-ion content, which accelerates the electron transport from NaBH4 to 4-NP to result in the catalytic reduction of 4-NP to 4-aminophenol (4-AP).