NiSe2@NixSy nanorod on nickel foam as efficient bifunctional electrocatalyst for overall water splitting

Abstract

Electrocatalytic water splitting technology has become one of the most promising methods to solve the energy crisis, which can produce a large amount of high purity H2 and O2. It is necessary to develop efficient and stable water splitting catalyst for reducing the overpotential of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) and accelerating their reaction kinetics. A series of NiSe2@NixSy nanoarrays was firstly in situ grown on the nickel foam through the typical hydrothermal, selenylation and sulfuration pathways. The Na2SeO3 homogeneous solution is formed by hydrothermal and the selenization process is done at the temperature of 180。C. Then the nickel foam (NF) is put into the Na2SeO3 solution to form NiSe2 material at the temperature of 120。C. After that, the NiSe2 materials were sulfuretted with different amounts of sulfur to form NiSe2@NixSy hybrid materials. The experimental results demonstrate that the NiSe2@NixSy material as a 3D electrode can maximize the synergistic reaction between NiSe2 and NixSy, thus exhibiting an efficient and comprehensive water splitting performance. The NiSe2@NixSy-1 material presents a superior OER performance with requiring the overpotential of only 206 mV at 100 mA cm−2. Moreover, the NiSe2@NixSy-0.3 material presents a superior HER performance with requiring the overpotential of only 148 mV at 100 mA cm−2. It is worth noting that when NiSe2@NixSy-1 material and the NiSe2@NixSy-0.3 material was used as cathode and anode, only 1.53 V cell voltage is needed to produce a current density of 10 mA cm−2 throughout the water splitting process, which is one of the smallest values reported so far. Density functional theory calculations results show that the Ni3S2 has the best water adsorption energy, so it is an active species in the process of catalysis. However, NiSe2 has more density distribution around the Fermi level, indicating that it exhibits better metallic properties, which makes the NiSe2@NixSy-1 hybrid material exhibit better electronic conductivity.