Monolayer Ti3C2Tx as an Effective Co-catalyst for Enhanced Photocatalytic Hydrogen Production over TiO2

Titanium dioxide (TiO2) represents a promising candidate for hydrogen production via photocatalysis. However, its large bandgap and fast charge recombination limits its efficiency. To overcome this limitation, we explored in this work two-dimensional titanium carbide MXene, Ti3C2Tx (Tx = O, OH, F), as feasible co-catalysts for hydrogen production with TiO2 as the photocatalyst. We synthesized a series of Ti3C2Tx/TiO2 composite photocatalysts with monolayer Ti3C2Tx as the co-catalyst to improve the separation of photoinduced electrons and holes. The physicochemical properties of the Ti3C2Tx/TiO2 composites were investigated by a variety of characterization techniques, and the effect of the monolayer Ti3C2Tx on the photocatalytic performance of the Ti3C2Tx/TiO2 composites is elucidated by comparison to the multilayer counterpart. The photocatalytic hydrogen evolution rate of the optimized monolayer Ti3C2Tx/TiO2 composite is over 9 times higher than that of the pure TiO2 and 2.5 times higher than the multilayer counterpart. The significantly enhanced activity is attributed to the superior electrical conductivity of monolayer Ti3C2Tx and charge-carrier separation at the MXene/TiO2 interface. A mechanism of photocatalytic hydrogen evolution over the Ti3C2Tx/TiO2 system is proposed. This work demonstrates the potential of monolayer MXenes as effective co-catalysts for photocatalysis and further broadens the applications of the MXene family of two-dimensional materials.