Morphology engineering of 3D nanostructure MMNS as bifunctional electrocatalysts towards high-efficient overall water splitting

Abstract

It is highly desired but still a significant challenge to construct preeminent non-noble metal bifunctional electrocatalysts for large-scale electricity-to-hydrogen generation. In the paper, four novel morphologies of MMNS including epiphyllum-like MMNS-NFs1, ice flower-like NFs2, grape-like NRs1, and nanorod NRs2 were successfully achieved via a facile two-step process by adjusting C2H5NS/CO(NH2)2 M ratio and/or H2O/ethanol solvent composition. Electrochemical activities of as-prepared four samples were systematically studied, while 3D nanorods core-shell nanostructure MMNS-NRs2 exhibits high-efficient electrocatalytic performance towards HER (158 mV @ 10 mA cm−2) and OER (134 mV @ 40 mA cm−2). What's more, when MMNS-NRs2 was served as the cathode and anode for overall water splitting in 1.0 M KOH, only a low cell voltage of 1.52 V and 1.60 V were required for MMNS-NRs2//MMNS-NRs2 electrode pairing to reach the current density 20 mA cm−2 and 100 mA cm−2, respectively. MMNS-NRs2//MMNS-NRs2 also performs an outstanding long-term durability at least 16 h without obvious deactivation. The reason for outstanding electrochemical properties and stability of MMNS-NRs2 was owing to the fact that unique core-shell nanostructure can facilitate electron/ion transfer and mass transport, 3D nanosheets endow more active sites and higher electron transport rate and the synergistic effect of Mo and Mn composition. This work provides a well-designed structure and development for morphology engineering to construct high-performance material for clean energy conversion technologies.