Selenium anion substitution endows manganese sulfide as a bifunctional electrocatalyst for efficient water splitting in alkaline solutions

Currently, it is still highly desirable to develop high activity, cost-effective and stable electrocatalyst for accomplishing robust water splitting. Due to its excellent electroconductivity and large atomic ratio, transition metal sulfides or selenides have been extensively designed and highly-developed for the electrocatalysts field. Herein, a novel Tribulus terrestris like nanostructure MnSxSe1-x@N,F-CQDs nanocomposites with abundant defects was designed based on successive strategy including microwave-assisted heating, hydrothermal and calcination. Benefiting from its distinctive chemical structure and morphology, the as-developed MnSxSe1-x@N,F-CQDs possesses impressive electrocatalytic activities under alkaline condition with low overpotentials of 209 mV for oxygen evolution reaction (OER) and 87 mV for hydrogen evolution reaction (HER) at the current density of 10 mA cm−2, simultaneously yielding low Tafel slope of 72.18 and 78.19 mV dec−1. The MnSxSe1-x@N,F-CQDs also exhibits remarkable long-term stability. Importantly, when utilized as the bifunctional electrode for overall water splitting, the MnSxSe1-x@N,F-CQDs||MnSxSe1-x@N,F-CQDs merely requires an applied voltage of 1.55 V at 10 mA cm−2 and diplays prominent durability, which is almost comparable with that of the noble metal based RuO2‖Pt/C system. This work gains a new insight into the rational construction and exploration of inexpensive and high-efficient transition metal sulfides/selenides bifunctional electrocatalyst for overall water splitting by CQDs induction coupled with anionic substitution strategies.