Vacancy-occupation triggered phase transformation in molybdenum disulfide with reduced energy barrier for enhanced alkaline water electrolysis

Optimizing the energy barrier of 2H-to-1T phase transformation plays a crucial role in modulating the intrinsic electronic structure of MoS₂ to achieve satisfactory water-splitting performance, but remains a significant challenge. Herein, we report a vacancy occupation-triggered phase transition strategy to fabricate a core–shell 1T phase nanorod structure, which is composed of S-vacancies decorated MoS₂ as the core, and N, P co-doped carbons as the shell (1T-MoS₂@NPC). The co-insertion of N and P dopants into MoS₂ can occupy partial S-vacancies, triggering a phase transformation from the semiconducting 2H phase to the conducting 1T phase with a reduced energy barrier. Profiting from the strong coupling effect between N, P dopants and S-vacancies, the as-made 1T-MoS₂@NPC exhibits excellent electrocatalytic activity for both HER (η₁₀ = 148 mV) and OER (η₁₀ = 232 mV) in alkaline solution. Meanwhile, a low cell voltage of 1.62 V is needed to drive a current density of 10mA cm⁻² in 1.0 M KOH electrolyte. The theoretical calculation results reveal that the S-vacancies decorated C atoms in the meta-position relative to N, P atoms represent the most active HER and OER sites, which synergistically upshift the d band center and balance the rate-determining step, thus ensuring the simultaneous optimization of adsorption free energy and electronic structure. This vacancy-occupation-derived phase transformation strategy caused by non-metallic doping may provide valuable guidance for enhancing the performance of alkaline water electrolysis.