Heterostructured MoO2@MoS2@Co9S8 nanorods as high efficiency bifunctional electrocatalyst for overall water splitting

Abstract Developing low-cost and high-efficiency bifunctional catalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to catalyze electrochemical overall water splitting is critical for the production of hydrogen. Herein, we develop an in-situ reduction and vulcanization strategy to prepare MoO2@MoS2@Co9S8 heterostructure nanorods by utilizing MoO3@ZIF-67 as a precursor. The reduction of MoO3 can produce more conductive MoO2, and the vulcanization reaction can produce highly active MoS2 for the HER as well as highly active Co9S8 for the OER. In addition, the MoS2 anchor on the MoO2 not only facilitates electron transfer, but also interacts with Co9S8 to induce a synergic catalytic effect by the electron transfer between them. Moreover, the 2D nanosheet assembled heterostructure nanorods can provide a large electrochemical surface area. Therefore, the merits of the materials are fully utilized and outstanding catalytic performances are achieved. MoO2@MoS2@Co9S8 can catalyze HER and OER effectively with overpotentials of 160 and 310 mV at 10 mA cm−2, indicating its bifunctional activity. In addition, the two electrode electrolyzer catalyzed by MoO2@MoS2@Co9S8 can reach 10 mA cm−2 current density at a cell voltage of 1.62 V with very high stability, demonstrating its practical application for water splitting.