Band structure engineering and interfacial charge modulation in ReS2/1T′-MoS2 and ReS2/1T′-WS2 heterostructures for tunable hydrogen adsorption

In this work, we employ first-principles calculations including the spin–orbit coupling effects (SOC) to investigate the electronic structure and hydrogen evolution reaction (HER) activity of two novel heterostructures, ReS2/1T′-WS2 and ReS2/1T′-MoS2. Our results demonstrate the potential of ReS2 to form stable heterostructures with monolayers of metastable 1T′ phases of WS2 and MoS2, respectively. The strong in-plane anisotropy of the 1T′ layers, combined with interlayer hybridization and charge redistribution, activates additional interfacial adsorption sites. As a result, both the heterostructures exhibit superior hydrogen evolution reaction (HER) activity compared to their monolayer 1T′ counterparts. By calculating the change in Gibbs free energy of hydrogen adsorption (ΔGH) at top, bottom, and interfacial sites, we identify the most favorable adsorption sites contributing to HER activity. Our results show that the minimum ΔGH is 0.15 eV for ReS2/1T′-WS2, and ReS2/1T′-MoS2 exhibits even better HER activity with nearly optimal ΔGH of 0.02 eV. These findings highlight the possibility of band structure engineering in these heterostructures, with ReS2 as a viable approach to stabilize the metastable phases and further achieve enhanced HER activity. In addition, this strategy offers a promising pathway toward efficient and earth abundant alternatives to noble-metal electrocatalysts.