C-Doped KNbO3 single crystals for enhanced piezocatalytic intermediate water splitting

Abstract

H₂O₂ is an environmentally friendly chemical for wide water treatments and H₂ is regarded as an ideal substitute for traditional fossil energy. The industrial production of H₂O₂ is via the anthraquinone oxidation process, which, however, consumes extensive energy and produces pollution. Herein, based on the density functional theory (DFT) calculations, we report a green and sustainable piezocatalytic intermediate water splitting (IWS) process to simultaneously obtain H₂O₂ and H₂ using C-doped KNbO₃ nano single crystals as catalysts. The KNbO₃ catalysts doped with suitable amounts of carbon show an enhanced water splitting rate, which could be attributed to the decreased reaction barriers on the C-KNbO₃ surface and improved polarized built-in electric field, as evidenced by DFT simulations and PFM measurements. Remarkably, the piezocatalytic H₂ evolution efficiency of 0.5 : 1 C-KNbO₃ reaches 524.51 μmol g⁻¹ h⁻¹. Additionally, 0.5 : 1 C-KNbO₃ could generate H₂ and H₂O₂ simultaneously through two-electron piezocatalytic IWS reactions. This improved catalytic efficiency is attributed to the promoted piezo-response of KNbO₃ after C doping, as revealed by PFM tests.