Three-dimensional supramolecular phosphomolybdate architecture-derived Mo-based electrocatalytic system for overall water splitting

Abstract

With hydrogen bond-directed three-dimensional phosphomolybdate-based supramolecular architecture as a precursor, a Mo₂C composite material (Mo₂C@NC) supported by nitrogen-doped carbon matrix was fabricated successfully through calcination. In this composite material, Mo₂C particles with size about 5 to 8 nm disperse evenly in the framework of nitrogen-doped mesoporous carbon matrix. In acid media, to achieve a current density of 10 mA cm⁻², the overpotential required was 142 mV with a Tafel slope of 63 mV dec⁻¹. Under basic conditions, the overpotential reduced to as low as 56 mV with a Tafel slope of 59 mV dec⁻¹. To realize overall water splitting, MoO₂-based composite material (MoO₂@NC) with nitrogen-doped carbon as matrix was obtained using the same precursor as Mo₂C@NC. MoO₂@NC exhibits excellent oxygen evolution reaction (OER) performance with an over potential of 302 mV. With Mo₂C@NC as cathode and MoO₂@NC as anode, an efficient electrolyzer was constructed, which required a cell voltage of 1.60 V to achieve a current of 10 mA cm⁻² in 1.0 M KOH. Furthermore, besides overall water splitting, Mo₂C@NC also shows striking catalytic removal property towards 4-nitrophenol and Rhodamine B.