High efficiency photocatalytic hydrogen production over ternary Cu/TiO2@Ti3C2Tx enabled by low-work-function 2D titanium carbide

It is of prime importance to harness the transfer and flow of photogenerated electrons and holes to elongate the lifetimes of charge carriers and enhance the activity of semiconductor photocatalyst, which can be achieved by hybridizing the photocatalyst with appropriate cocatalysts with right electronic properties and placement. Herein, MXenes, a young family of two-dimensional transition metal carbides, are exploited as a hole mediator to enhance the photocatalytic activity of TiO2. We grow TiO2 sheets exposing (001) surfaces on layered Ti3C2Tx, and then photodeposited Cu2O nanodots on TiO2. We experimentally prove that the Ti3C2Tx MXene from the wet HF etching method behaves as a low work function material (ϕ = 3.4 eV). Thanks to this unique electronic property, the photogenerated electrons on TiO2 hybridized with Ti3C2Tx accumulate and tunnel to Cu2O to reduce it to elemental Cu as a reduction cocatalyst. The resulting Cu/TiO2@Ti3C2Tx photocatalyst efficiently split water to produce hydrogen at 860 μmol g−1 h−1. The results presented here demonstrate the promise of MXene materials in photocatalytic solar energy utilization. The insight into the electronic property of MXene sheds light on the new approach to the rational design of high-efficiency photocatalysts composed of MXenes.