2D/2D Mo2CTx/g-C3N4 with a strong coupling interface via one-step NH4Cl-assisted calcination for enhanced photocatalytic hydrogen production†

Abstract

Mo₂CT_x is regarded as a potential cocatalyst to substitute noble metals in photocatalytic hydrogen production owing to its good electrical conductivity and a large number of active sites. However, Mo₂CT_x-based photocatalysts by the conventional physical mixing method always display a weak coupling interface between Mo₂CT_x and photocatalysts due to the large block-layered structure of Mo₂CT_x, which results in slow photogenerated-electron transfer of photocatalysts, thereby leading to unsatisfactory hydrogen production efficiency. Considering that in situ construction and the 2D/2D structure can increase the contact area and enhance the coupling interface interaction, in this study, a strategy of constructing a 2D/2D Mo₂CT_x/g-C₃N₄ photocatalyst from pre-etched Mo₂CT_x and guanidine hydrochloride (CH₆ClN₃) through a one-step NH₄Cl-assisted calcination method is realized by the gas-expansion exfoliation of Mo₂CT_x and in situ generation of thin g-C₃N₄ nanosheets. Experimental results unveiled that the 2D/2D Mo₂CT_x/g-C₃N₄ composite photocatalyst exhibits an exceptional H₂-evolution activity (125 μmol h⁻¹ g⁻¹, AQE = 3.88%), which is almost 25 and 18 times greater than that of pure g-C₃N₄ and physically mixed Mo₂CT_x–g-C₃N₄, respectively. The enhanced photocatalytic H₂-production efficiency is attributed to the robust coupling interface between Mo₂CT_x and g-C₃N₄ in 2D/2D Mo₂CT_x/g-C₃N₄, which promotes the fast photogenerated electron transfer from g-C₃N₄ to Mo₂CT_x and achieves an optimized Gibbs free energy. This study offers a novel perspective on preparing high-efficiency 2D/2D MXene-based photocatalysts.