Metallic\n1T-Li_<i>x</i>MoS₂ Cocatalyst Significantly\nEnhanced the Photocatalytic H₂ Evolution over Cd_0.5Zn_0.5S Nanocrystals under Visible Light Irradiation

Abstract

In\nthe present work, metallic 1T-Li_<i>x</i>MoS₂ is utilized as a novel cocatalyst for Cd_0.5Zn_0.5S photocatalyst. The obtained Li_<i>x</i>MoS₂/Cd_0.5Zn_0.5S hybrids show excellent\nphotocatalytic performance for H₂ generation from aqueous\nsolution containing Na₂S and Na₂SO₃ under splitting visible light illumination (λ ≥ 420\nnm) without precious metal cocatalysts. It turns out that a certain\namount of intercalating Li⁺ ions ultimately drives the\ntransition of MoS₂ crystal from semiconductor triagonal\nphase (2H phase) to metallic phase (1T phase). The distinct properties\nof 1T-Li_<i>x</i>MoS₂ promote the efficient\nseparation of photoexcited electrons and holes when used as cocatalyst\nfor Cd_0.5Zn_0.5S photocatalyst. As compared to\n2H-MoS₂ nanosheets only having edge active sites, photoinduced\nelectrons not only transfer to the edge sites of 1T-Li_<i>x</i>MoS₂, but also to the plane active sites\nof 1T-Li_<i>x</i>MoS₂ nanosheets. The\ncontent of Li_<i>x</i>MoS₂ in hybrid\nphotocatalysts influences the photocatalytic activity. The optimal\n1T-Li_<i>x</i>MoS₂ (1.0 wt %)/Cd_0.5Zn_0.5S nanojunctions display the best activity\nfor hydrogen production, achieving a hydrogen evolution rate of 769.9\nμmol h^–1, with no use of noble metal loading,\nwhich is about 3.5 times higher than that of sole Cd_0.5Zn_0.5S, and 2 times higher than that of 2H-MoS₂ (1.0 wt %)/Cd_0.5Zn_0.5S samples. Our results\ndemonstrate that Li⁺-intercalated MoS₂ nanosheets\nwith high conductivity, high densities of active sites, low cost,\nand environmental friendliness are a prominent H₂ evolution\ncocatalyst that might substitute for noble metal for potential hydrogen\nenergy applications.