Enhanced electron transport through a nanoforest-like structure of CoNi nanoalloy@nitrogen-doped carbon nanotubes for highly efficient catalysis of overall water splitting

Abstract

A major challenge of water splitting is to develop a robust bifunctional electrocatalyst. However, the catalytic effect of the reported materials is still unsatisfactory due to discrete electron transport, poor conductivity and limited active site. Herein, the nanoforest-like structure of CoNi@NC-NCNTs is fabricated by a facile carbonization-induced in situ growth strategy with nitrogen-doped carbon layer coated CoNi alloy nanowires (CoNi@NC) as trunks and intertwined nitrogen-doped carbon nanotubes as branches (NCNTs). The intertwined NCNTs grown on CoNi@NC nanowires not only build a highway of the electron transport between CoNi@NC nanowires, but also provide a continuous 3D conductive network for the whole electrocatalyst. Meantime, such structure increases the electrical conductivity and the catalytic activity site of CoNi@NC-NCNTs. Combined with the above advantages, the nanoforest-like CoNi@NC-NCNTs electrode exhibits high HER and OER catalytic performance in 1 M KOH solution with low overpotentials of 85 mV and 263 mV at 10 mA cm−2 and outstanding durability, respectively. The two-electrode electrolyzer assembled by CoNi@NC-NCNTs only requires 1.62 V to reach the current density of 10 mA cm−2. This paper provides a well-defined model for constructing highly efficient catalyst toward overall water splitting.