Releasing Au Electrons to Mo Site for Weakened Mo<i>─</i>H Bond of Mo₂C MXene Cocatalyst Toward Improved Photocatalytic H₂ Production

Mo₂C MXene (Mo₂CT_x) is one of the most promising noble-metal-free cocatalysts for photocatalytic H₂ production because of its excellent electron transport capacity and abundant Mo sites. However, Mo₂CT_x typically exhibits a strong Mo─H_ads bond, resulting in that the produced H₂ difficultly desorbs from the Mo surface for the limited activity. To effectively weaken the Mo─H_ads bond, in this paper, a regulation strategy of electron donor Au releasing electrons to the d-orbitals of Mo sites in Mo₂CT_x is proposed. Herein, the Mo₂CT_x-Au/CdS photocatalysts are prepared through a two-step process, including the initial loading of Au nanoparticles on the Mo₂CT_x surface and the subsequent in situ growth of CdS onto the Mo₂CT_x-Au surface. Photocatalytic measurements indicate that the maximal H₂-production rate of Mo₂CT_x-Au/CdS reaches up to 2799.44 µmol g^-1 h^-1, which is 30.99 and 3.60 times higher than that of CdS and Mo₂CT_x/CdS, respectively. Experimental and theoretical data corroborate that metallic Au can transfer free electrons to Mo₂CT_x to generate electron-enriched Mo^δ- sites, thus causing the increased antibonding-orbital occupancy state and the weakened Mo─H_ads bond for the boosted H₂-production efficiency. This research provides a promising approach for designing Mo₂CT_x-based cocatalysts by regulating the antibonding-orbital occupancy of Mo sites for improved photocatalytic performance.