Hydrogen adsorption-induced catalytic enhancement over Cu nanoparticles immobilized by layered Ti3C2 MXene

Electronic interaction at metal/support interfaces could change the electronic structure and catalytic activity of a metal. Herein, Cu nanoparticles (NPs) with sizes of (similar to)5 nm were uniformly deposited on two-dimensional titanium carbide MXene (Ti3C2). Some electrons transferred from Cu to Ti3C2 upon hybridization as evidenced by XPS analysis and DFT calculations. The work function (5.78 eV) of Ti3C2 was higher than that (4.63 eV) of Cu NPs, which was responsible for the interfacial charge transfer. Upon formation of Cu/Ti3C2, the d-band center (epsilon(d)) of Cu was shifted upwards from -2.38 eV to -2.27 eV with reference to Fermi energy. The calculated hydrogen adsorption energy (-2.57 eV) of Cu/Ti3C2 was higher than that (-2.45 eV) of unsupported Cu NPs. Such favorable hydrogen adsorption of Cu/Ti3C2 increased the number of surface-adsorbed hydrogen atoms, beneficial for the hydrogen-involved redox from the viewpoint of kinetics. Cu/Ti3C2 showed a promising catalytic activity for the reduction of 4-nitrophenol into 4-aminophenol with a normalized rate constant of 43.1 min(-1) mg(-1), which was 6.3 times as high as that of Cu NPs. Such enhanced catalysis was ascribed to the favorable hydrogen adsorption and good hydrophilicity of the nanohybrid. This work presents an example that the catalytic activity of Ti3C2 MXene-supported metals can be promoted by their hydrogen adsorption, which will broaden the application of other 2D MXene materials in catalysis.