Synthesis and characterizations of graphene/Sm doped BiFeO3 composites photoanode for efficient photo-electrochemical water splitting

The present study features Bi1-xSmxFeO3 (BSFO) nanoparticles anchored on high-quality, reduced graphene oxide (RGO) sheets via a two-step ultrasonication method for photo-electrochemical (PEC) studies relating to solar hydrogen generation. Sm doping leads to the formation of pure BFO type phase without any secondary phases. The structural, morphological, optical, and local structure analyses of BSFO and BSFO@RGO have been done through X-ray diffraction, scanning electron microscope, UV–Vis spectrophotometer, and Raman spectrometer, respectively. The BSFO nanoparticles have been templated on reduced graphene oxide. The BSFO@RGO has been employed as a photoanode for PEC measurements under the simulated solar irradiation of intensity 100 mW-cm−1. The optimum photoanode has been found with Bi0.95S0.05FO3@RGO. The highest photocurrent density and solar to hydrogen (STH) conversion efficiency have been found as 2.40 mA/cm2 (at 0.5 V vs. saturated calomel electrode) and 2.45%, respectively. Furthermore, the stability of the photoanode against photo corrosion has also been tested by the chronoamperometric technique. During 2 h experiment, the average photocurrent density has been maintained at 1.5 mA/cm2 (at 0 V vs. SCE). The improved photocatalytic activity of BSFO@RGO has been explained based on the effect of doping, better solar spectral response, hindering the recombination loss of photo-generated charge carriers, and fast, facile charge transport. Although earlier studies have used Bi(Sm)FeO3 photoanode, hydrogen production has been observed for the first time in the present investigation to the best of our knowledge. Also, it appears that hydrogen production at zero external bias as observed in the present study suggests a new feature for bandgap tailored BFO.