Preparation of Oxygen-Doped Amorphous MoS2 and Its Electrocatalytic Performance for Nitrogen Reduction to Ammonia

Abstract

The electrocatalytic nitrogen reduction reaction (NRR) is a key approach for synthesizing green ammonia under mild conditions. However, the high bond energy of the N≡N triple bond makes N2 difficult to activate, limiting the Faradaic efficiency. MoS2 offers advantages such as low cost and abundant reserves as a non-precious-metal NRR electrocatalyst. Nevertheless, pure MoS2 suffers from insufficient conductivity and a limited number of active sites, resulting in suboptimal catalytic performance. Herein, we develop a solvent-regulated one-step hydrothermal strategy using ethylene glycol as the sole reaction medium to fabricate an oxygen-substituted amorphous MoS2 (O-MoS2) electrocatalyst. XRD, SEM, and HRTEM characterization revealed that, as the ethylene glycol ratio increased, the product gradually transformed from a layered crystalline structure to a completely amorphous structure. XPS confirmed that oxygen atoms were uniformly incorporated into the MoS2 lattice via substitution doping. Electrochemical testing showed that O-MoS2 achieved an ammonia yield of 97.16 μg h−1 mg−1 and a Faradaic efficiency of 46.44% in a 0.1 M Na2SO4 electrolyte at −0.70 V vs. RHE, significantly outperforming undoped MoS2 and semi-doped S-MoS2. DFT calculations indicate that O doping reduces the N2 adsorption energy, thereby synergistically promoting N2 adsorption and activation. This dual-modification strategy provides a facile and universal guidance for electronic structure regulation of MoS2-based catalysts and sheds new light on the design of high-efficiency ambient nitrogen fixation electrocatalysts toward practical green ammonia synthesis.