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 ∼4.2 mA cm−2 was recorded attributing to the effective charge separation of efficiency of ∼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 (H2) and oxygen (O2) 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.
This work was supported by Ajou University. The researchers at the Green Hydrogen Lab (UQTR Institute for Hydrogen Research) would like to acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC) Tier 1 Canada Research Chair in Green Hydrogen Production, the Qu\u00e9bec Minist\u00e8re de l'\u00c9conomie, de l'Innovation et de l'\u00c9nergie (MEIE) [D\u00e9veloppement de catalyseurs et d'\u00e9lectrodes innovants, \u00e0 faibles co\u00fbts, performants et durables pour la production d'hydrog\u00e8ne vert, funding reference number 00393501], and Innergex Renewable Energy Inc. for the Innergex Research Chair in Renewable Hydrogen Production.
