Metal-Doped Knbo3 For Visible Light Photocatalytic Water Splitting: A First Principles Investigation

Materials suitable for visible light photocatalytic water splitting provide sustainable green energy production and environmental pollution solution. Potassium niobate, KNbO3, is not widely used in photocatalytic applications because of its large bandgap, which is not appropriate for the visible range of the solar spectrum. However, doping of semiconductors may help reduce their bandgaps by pinning a dopant level near the top/bottom of the valence/conduction band. We employ first-principles calculations to gain insight into the electronic and optical properties of KNbO3 doped with a number of 3d and 4d transition metals to design and enhance its photocatalytic behavior. We demonstrate the substitutional doping with these elements at the Nb site decreases the bandgap and improves the optical and photocatalytic activities of KNbO3. Our calculations prove that the best candidates for water splitting and CO2 gas reduction are Ag- and Mn-doped KNbO3, respectively. Computational outcomes are compared and discussed with existing experimental ones for doped KNbO3 and KTaO3 structures. Meanwhile, we found out Tc-doped KNbO3 can be beneficial for spintronic applications. The results achieved in this study will initiate a number of experimental investigations for the full exploration of the cubic perovskites, especially in green energy production.