Co-Improvement in Electrocatalytic Hydrogen Evolution Performance of MoS2 by Ni Doping and Graphene Oxide Compounding.

Abstract

Molybdenum disulfide (MoS₂) is a promising catalyst for hydrogen evolution through water electrolysis with low cost and high efficiency, but its hydrogen evolution performance can be further improved. Using sodium molybdate (Na₂MoO₄·2H₂O) and thiourea (NH₂CSNH₂) as raw materials, MoS₂ was prepared by the hydrothermal method. Ni-doped MoS₂(Ni-MoS₂) was prepared by using nickel dichloride dihydrate (NiCl₂·2H₂O) as a Ni source and doping Ni into MoS₂ by the hydrothermal method. Under the conditions of different temperatures (190 °C, 200 °C, and 210 °C) and different Ni doping molar ratios (2%, 3%, and 4%), the optimum temperature and doping ratio of the prepared materials were explored by conducting a hydrogen evolution reaction (HER) by the electrolysis of water. The results showed that the optimum preparation temperature was 200 °C and the optimum molar ratio of Ni doping was 3%. Graphene oxide (GO) was obtained by oxidation of graphite (G), and then Ni-MoS₂/GO was prepared by the hydrothermal method with Ni-MoS₂ and GO. The performance of HER was tested. The materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), and X-ray photoelectron spectroscopy (XPS). The results show that the composite Ni-MoS₂/GO has good HER performance, which is better than that of MoS₂ or Ni-MoS₂. In 0.5 M H₂SO₄ solution, the η₁₀ is as low as 196 mV, the Tafel slope is 122 mV/dec, the C_dl is 13.98 mF/cm², and it has good stability. The enhancement of electrocatalytic activity is mainly due to the doping of a small amount of Ni, which increases the defects of the catalyst and forms more active sites. GO improves the conductivity of the material. Ni doping and GO compounding promote the HER performance of MoS₂.