Photoelectrochemical (PEC) water splitting is one of the potential approaches for the generation of hydrogen which can fulfill the global energy requirement . In developing economical and efficient photo-catalysts for water oxidation, n-type monoclinic BiVO4 has been widely reported due to its favorable band gap. But the photo conversion efficiency of BiVO4 catalyst is relatively low due to poor charge transport, fast surface charge recombination and sluggish water oxidation kinetics . In current report, BiVO4 photocatalyst doped with ytterbium (Yb) was prepared by ultrasonic spray coating technique to overcome poor charge transport. Various percentage of Yb (1,2,3,4,5 wt %) is doped in pristine BiVO4 to optimize the PEC performance. The 3wt % Yb doped BiVO4 photo-anode has shown highest PEC photo current 2.8 mA/cm2 at 1.23 V RHE and 5.8 mA/cm2 at 2 V RHE under simulated one sunlight illumination at front surface in K2HPO4 electrolyte. However, the photocatalytic activity of the other Yb: BiVO4 photo anodes were suppressed as the Yb doping level decreased or increased, which could be attributed to the formation of photogenerated charge carrier recombination centers at the Yb substituting sites. Here, Yb3+ dopant replaces Bi3+ sites in BiVO4 lattice to provide expanded light absorption wavelength region from 400-600nm. Further, Yb: BIVO4 photoanode were investigated by XRD, XPS and SEM. It was observed from XRD that Yb-doping didn’t generate any impurity phases in pristine BiVO4. XPS analysis showed the Yb-peaks 4d3/2 and 4d5/2 at the binding energies 193eV and 184eV respectively, which confirm the oxidation state of Yb as +3. The electrochemical impedance and cyclic voltametry measurements showed that the Yb doping lowered the interfacial resistance, charge transfer resistance and increased the charge donor/surface state density. Further PEC performance was corroborated with changes in band gap, crystal lattice, surface grain morphology occurred due to Yb doping in BiVO4.

Light Absorption management by systematic ytterbium doping in monoclinic BiVO4 for enhancement in photoelectrochemical water oxidation

2019 Spring National Meeting

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