Visible-Light-Induced Photocatalytic Activity of Stacked MXene Sheets of Y2CF2

Transition metal carbides, nitrides, and carbonitrides (MXenes) are emerging two-dimensional (2D) materials, with a variety of applications, such as heterogeneous catalysis, due to their metallic conductivity and resulting charge transport properties. However, the semiconductor photocatalysis of MXene-related materials has not been experimentally demonstrated. Here, we show that stacked MXene sheets of Y2CF2 behave as an n-type semiconductor, with a 1.9 eV band gap and a rather negative conduction band potential of approximately -2.1 V versus Ag/AgNO3 . In the presence of triethanolamine as an electron donor, Y2CF2 exhibits the ability to reduce protons into H-2 under visible light. However, Y2CF2 is not very stable during the photoreaction, even in the presence of triethanolamine, undergoing oxidative degradation to form fluorocarbon and carbonate species due primarily to the high-energy valence band formed by C 2p orbitals.