Visible-light-induced water reduction reaction for efficient hydrogen production by N-doped In2Ga2ZnO7 nanoparticle decorated on RGO sheets

Abstract

This work presents an efficient in situ chemical method for constructing graphene-based N-doped In₂Ga₂ZnO₇ nanocomposites (RGO/N-IGZ) for the production of hydrogen (H₂) under visible-light irradiation. Well-anchored N-doped IGZ nanoparticles on RGO sheets were successfully obtained by the hydrothermal route that was employed. Several crystallographic, microscopic, and spectroscopic methods (XRD, DRUV-vis, PL spectra, TRPL analysis, XPS, TEM, and photoelectrochemical and photostability measurements) were adopted to study the robust photocatalytic activity of all the synthesised photocatalysts. A DRS study revealed that doping an IGZ nanoparticle with N reduced its band gap (E_g) from 2.50 eV to 2.34 eV and, furthermore, the introduction of RGO into the N-IGZ nanoparticle altered its E_g to 2.29 eV. The loading amount of RGO in an N-IGZ nanoparticle played a crucial role in enhancing the photocatalytic H₂-producing ability of the N-IGZ nanoparticle. In the absence of a co-catalyst, a loading of RGO of only 2 wt% in N-IGZ enabled the production of the highest amount of H₂, i.e. 726 μmol h⁻¹, under visible-light irradiation. The superior photocatalytic activity of the 2RGO/N-IGZ nanocomposite in comparison with that of neat N-IGZ nanoparticles was demonstrated by correlation with the results obtained from BET surface area analysis, TEM, PL, TRPL, and photocurrent and photostability measurements, which concluded by showing better charge separation in the 2RGO/N-IGZ nanocomposite. 2RGO/N-IGZ exhibited low PL intensity, a longer average decay time (the values of <τ> for N-IGZ and 2RGO/N-IGZ were 2.11 and 7.11 ns, respectively), high photocurrent generation (42 times greater than that of N-IGZ), a large surface area and the production of the highest amount of H₂ under visible-light irradiation without using any co-catalyst.