Engineering Phase Stability of Semimetallic MoS₂ Monolayers for Sustainable Electrocatalytic Hydrogen Production

1T'-phase MoS₂ possesses excellent electrocatalytic performance, but due to the instability of the thermodynamic metastable phase, its actual electrocatalytic effect is seriously limited. Here, we report a wet-chemical synthesis strategy for constructing rGO/1T'-MoS₂/CeO₂ heterostructures to improve the phase stability of metastable 1T' phase MoS₂ monolayers. Importantly, the rGO/1T'-MoS₂/CeO₂ heterostructure exhibits excellent electrocatalytic hydrogen evolution reaction (HER) performance, which is much better than the 1T'-MoS₂ monolayers. The synergistic effects between CeO₂ nanoparticles (NPs) and 1T'-MoS₂ monolayers were systematically investigated. 1T'-MoS₂ monolayers combined with the cocatalyst of CeO₂ NPs can produce lattice strain and distortion on 1T'-MoS₂ monolayers, which can tune the energy band structure, charge transfer, and energy barriers of hydrogen atom adsorption (ΔE_H), leading to promotion of the phase activity and stability of 1T'-MoS₂ monolayers for hydrogen production. Our work offers a feasible method for the preparation of efficient HER electrocatalysts based on the engineering phase stability of metastable materials.