Cobalt single atoms supported on CNT/MoS2 heterojunction nanocomposite for highly-efficient reduction of 4-nitrophenol wastewater: Enhanced electron transport

Modulation of the electronic structure of heterogeneous catalysts by introducing heterojunctions is an effective means to improve their catalytic performance. Although Co-based nanocatalysts have been widely used in the reduction of 4-nitrophenol (4-NP) wastewater, Co single-atom catalysts (SACs) have rarely been reported. Herein, we successfully fabricate Co SACs supported on CNT/MoS2 heterojunction nanocomposite (Co1-MoS2/ CNT) by a hydrothermal synthesis combined with the subsequent impregnation method. The catalytic performance of Co1-MoS2/CNT is evaluated using the reduction of 4-NP in an aqueous media containing sodium borohydride. Complete reduction of 4-NP catalyzed by Co1-MoS2/CNT occurs within 5 min at room temperature, and the apparent rate constant k can reach 1.16 min- 1, which is 4.1 and 38.6 times higher than those of Co1-CNT and Co1-MoS2, respectively. The improved catalytic performance of Co1-MoS2/CNT is attributed to the p-n heterojunctions of MoS2/CNT increasing the electron density of the Co single-atom sites, as well as the CNTs with excellent conductivity, accelerating the electron transfer. Moreover, Co1-MoS2/CNT exhibits excellent stability and favorable applicability, endowing its potential for practical applications. Our findings not only provide useful insights into the enhancement of catalytic performance of SACs, but also open a new avenue for the treatment of 4-NP wastewater.