Ti₃C₂T_<i>x</i> 2D and 0D MXene Cocatalysts on CuO for Enhanced Photocatalytic Hydrogen Evolution

Cocatalysts play a crucial role in photocatalytic reactions, and titanium carbide MXene (Ti₃C₂T _<i>x</i> ) is a promising alternative to expensive noble metal cocatalysts. Herein, we coupled a copper-(II) oxide (CuO) semiconductor with Ti₃C₂T _<i>x</i> in two dimensions, nanosheets (T2D) and quantum dots (T0D), forming T2D/CuO and T0D/CuO composite photocatalysts. The effects of size, morphology, and energetics of the different Ti₃C₂T _<i>x</i> forms were investigated in relation to their photocatalytic hydrogen production rates. The T0D/CuO sample achieved a hydrogen production rate of 2174 (±189) μmol g^-1 h^-1, which is 19 and over 100 times higher than those of T2D/CuO samples and pure CuO, respectively. The enhanced performance of T0D/CuO compared to T2D/CuO can be attributed to a smaller particle size, improved light absorption, larger specific surface area, and a deeper T0D work function promoting charge separation for photocatalytic reactions. These results highlight the impact of the different dimensionalities of titanium carbide MXenes on the photocatalytic performance of composites and point to promising avenues to achieve efficient photocatalytic systems.