Boosted Hydrogen Evolution via Molten Salt Synthesis of Vacancy-Rich MoS<sub><i>x</i></sub>Se<sub>2–<i>x</i></sub> Electrocatalysts
Boxin Li, Ke Wang, Song He, Hongfang Du, Tingfeng Wang, Zhuzhu Du, Wei Ai
Abstract
MoS x Se 2– x emerges as a potent alternative to Pt-based electrodes in the electrochemical hydrogen evolution reaction (HER), although its practical application is hindered by suboptimal synthetic methods. Herein, a KSCN molten salt strategy is introduced, enabling the straightforward synthesis of MoS x Se 2– x at a modest temperature of 320 °C through a one-step heating process involving Se powder and Na 2 MoO 4 in a muffle furnace. It is elucidated that MoO 4 2– facilitates the decomposition of KSCN to S 2–, which subsequently activates Se powder, culminating in the formation of the Se x S 2– polyanion. This polyanion then interacts with MoO 4 2–, yielding MoS x Se 2– x characterized by a profusion of anion vacancies. This is attributed to the introduction of Se heteroatoms, causing lattice distortion and the substantial steric hindrance of Se x S 2–, limiting crystal growth. Theoretical analyses indicate that the presence of Se atoms and anion vacancies collaboratively modulates the electronic structure of MoS x Se 2– x . This results in a minimized band gap of 0.88 eV and an almost zero Δ G H* of 0.09 eV in the optimized MoS 1.5 Se 0.5 . Consequently, MoS 1.5 Se 0.5 exhibits remarkable HER performance, characterized by a low η 10 of 103 mV and a minimal Tafel slope of 33 mV dec –1, alongside robust stability. This research not only unveils a potent electrocatalyst for HER but also introduces a simplified synthesis strategy for transition metal selenosulfides, broadening their applicability across various domains.