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

Mo2CTx 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, Mo2CTx-based photocatalysts by the conventional physical mixing method always display a weak coupling interface between Mo2CTx and photocatalysts due to the large block-layered structure of Mo2CTx, 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 Mo2CTx/g-C3N4 photocatalyst from pre-etched Mo2CTx and guanidine hydrochloride (CH6ClN3) through a one-step NH4Cl-assisted calcination method is realized by the gas-expansion exfoliation of Mo2CTx and in situ generation of thin g-C3N4 nanosheets. Experimental results unveiled that the 2D/2D Mo2CTx/g-C3N4 composite photocatalyst exhibits an exceptional H-2-evolution activity (125 mu mol h(-1) g(-1), AQE = 3.88%), which is almost 25 and 18 times greater than that of pure g-C3N4 and physically mixed Mo2CTx-g-C3N4, respectively. The enhanced photocatalytic H-2-production efficiency is attributed to the robust coupling interface between Mo2CTx and g-C3N4 in 2D/2D Mo2CTx/g-C3N4, which promotes the fast photogenerated electron transfer from g-C3N4 to Mo2CTx and achieves an optimized Gibbs free energy. This study offers a novel perspective on preparing high-efficiency 2D/2D MXene-based photocatalysts.