Manipulating photocatalytic pathway and activity of ternary Cu2O/(001)TiO2@Ti3C2Tx catalysts for H2 evolution: Effect of surface coverage

Abstract

A Cu2O/(001)TiO2@Ti3C2Tx photocatalyst was synthesized via a wet-chemistry reduction method by N, N-dimethylformamide (DMF). By scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), it was revealed that the surface coverage of photocatalyst increased with the loading amount of Cu2O, while the particle size of Cu2O did not change significantly. The photocatalytic activity and mechanism of ternary Cu2O/(001)TiO2@Ti3C2Tx photocatalyst heavily depend on the surface coverage of copper species. When the surface coverage of photocatalyst by Cu2O was low, the Ti3C2Tx acted as hole reservoir. Cu2O was firstly reduced in situ to metallic copper by excited electrons. Then the reverse movement of carriers enabled the spatial separation of photogenerated electron-hole pairs, and afforded relatively high hydrogen evolution (more than 1100 μmol h−1 (g CuOx TiO2)−1). When the coverage of Cu2O on (001)TiO2@Ti3C2Tx was too high at high loading amounts, Ti3C2Tx failed to play the role of hole trapping. Under that circumstance, the photocatalytic reaction follows p-n junction mechanism, leading to low hydrogen productivity. The results here shed light on the relationship between structure and activity of Cu2O/(001)TiO2@Ti3C2Tx, which was conducive to the development of the MXene-based photocatalysts.