Effect of graphene oxide on the energy level alignment and photocatalytic performance of Engelhard Titanosilicate-10

Abstract

A smaller band gap with lower electron-hole recombination is required to ensure good photocatalytic performance of a photocatalyst. This study reveals that the incorporation of graphene oxide (GO) into Engelhard Titanosilicate-10 (ETS-10) forms GO/ETS-10 material with reduced optical band gap of about 2.9 eV, thereby making the GO/ETS-10 material a functional photocatalyst under regions of visible and ultraviolet radiations. Moreover, the results of ultraviolet photoelectron and low-energy inverse photoelectron spectroscopy (UPS-LEIPS) show that GO is a good platform for ETS-10, which significantly lowers the electronic band gap (Eg = 4.005 eV) between the highest occupied (HOMO) and lowest unoccupied molecular orbitals (LUMO) to ease electron transport, significantly reduces the work function (WF = 4.357 eV) to facilitate excitation of electron, and significantly increases the electron affinity (EA = 4.179 eV) to slow down the electron-hole recombination. The results are in good agreement with the empirical photocatalytic degradation of aqueous methylene blue (MB) by the GO/ETS-10 material. Under ultraviolet light irradiation, photocatalytic degradation of MB by the GO/ETS-10 material (as GO/ETS-10/UV-A) shows a similar degradation rate (k1 = 1.6 × 10−3 min−1) in comparison to that under visible light irradiation (as GO/ETS-10/Vis) (k1 = 1.6 × 10−3 min−1), and double the degradation rate in comparison to that in the ETS-10/UV-A system (k1 = 0.7 × 10−3 min−1). Furthermore, the addition of 10 mM of hydrogen peroxide (H2O2) into the photocatalytic system significantly increases the rate of MB degradation with k1 = 4.8 × 10−3 min−1 for the GO/ETS-10/H2O2/UV-A system and k1 = 2.9 × 10−3 min−1 for the GO/ETS-10/H2O2/Vis system. This study illustrates that UPS-LEIPS can be a good technique to predict the performance of a solid photocatalyst, and the GO/ETS-10 material is a good photocatalyst for the degradation of organic pollutants in water.