Enhanced photoactivity towards bismuth vanadate water splitting through tantalum doping: An experimental and density functional theory study

The activation of hole trap states in bismuth vanadate (BiVO4) is considered an effective strategy to enhance the photoelectrochemical (PEC) water-splitting activity. Herein, we propose a theoretical and experimental study of tantalum (Ta) doping to BiVO4 leading to the introduction of hole trap states for the enhanced PEC activity. The doping of Ta is found to alter the structural and chemical surroundings via displacement of vanadium (V) atoms that cause distortions in the lattice via the formation of hole trap states. A significant enhancement of photocurrent to similar to 4.2 mA cm(-2) was recorded attributing to the effective charge separation of efficiency of similar to 96.7 %. Furthermore, the doping of Ta in the BiVO4 lattice offers improved charge transport in bulk and decreased charge transfer resistance at the electrolyte interface. The Ta-doped BiVO4 displays the effective production of hydrogen (H-2) and oxygen (O-2) under AM 1.5 G illumination with a faradaic efficiency of 90 %. Moreover, the density functional theory (DFT) study confirms the decrease in optical band gap and the activation of hole trap states below the conduction band (CB) with a contribution of Ta towards both valence and CB that increases the charge separation and majority charge carrier density, respectively. The findings of this work propose that the displacement of V sites with Ta atoms in BiVO4 photoanodes is an efficient approach for enhanced PEC activity.

Automated summary

This study investigates the introduction of hole trap states in bismuth vanadate (BiVO4) by tantalum (Ta) doping, which leads to enhanced photoelectrochemical (PEC) water-splitting activity. The doping of Ta alters the structure and chemical surroundings of BiVO4, forming hole trap states and causing lattice distortions. The photocurrent is significantly increased to 4.2 mA cm(-2) with an efficiency of 96.7%. DFT calculations confirm the decrease in optical band gap and the activation of hole trap states with the contribution of Ta, increasing charge separation and carrier density.