In Situ Construction of MnO<sub>2</sub>–Co<sub>3</sub>O<sub>4</sub> Nanosheet Heterojunctions on Co@NCNT Surfaces for Oxygen Evolution
Qiaoling Zhao, Zhenjiang Lu, Jing Xie, Jindou Hu, Yali Cao, Aize Hao
Abstract
Electrocatalytic water splitting is still circuitous and controversial because of the lack of highly active electrocatalysts to decrease the overpotential. Herein, we report a feasible method for constructing heterojunctions of MnO 2 –Co 3 O 4 nanosheets on Co@NCNT support surfaces (MnO 2 –Co 3 O 4 /Co@NCNT) by spontaneous redox reactions. Experimental results indicate that Co embedded in Co@NCNT can be used as the carbon support and anchoring sites for heterojunctions, thus exposing a large number of active sites, adjusting the surface electronic structure, changing the OER rate-determining step of the catalyst, and reducing the reaction energy barrier. Besides, the in situ formation of MnO 2 –Co 3 O 4 nanosheets on Co@NCNT inhibits the loss and aggregation of the catalyst, leading to robust structural stability. Therefore, the synergistic effects of these factors provide multi-functional active sites to enhance the intrinsic activity and achieve maximum catalytic performances. To deliver a current density of 10 mA cm –2, the catalyst of MnO 2 –Co 3 O 4 /Co@NCNT achieves an overpotential (η) of 303 mV in 1.0 M KOH media for OER. This simple redox strategy can be easily extended to prepare other ultrathin transition-metal oxide heterojunctions, which could be applied not only for water splitting but also for other energy conversion and storage technologies.