Na-Sm Bimetallic Regulation and Band Structure Engineering in CaBi₂Nb₂O₉ to Enhance Piezo-photo-catalytic Performance

The piezoelectric enhancement of photo-catalytic activity for water splitting and pollutant degradation is a novel approach to developing renewable energy and environmental protection applications. Herein, a new form of defect engineered Na-Sm bimetallic-regulated CaBi₂Nb₂O₉ platelet is synthesized via a molten salt process for water splitting and pollutant degradation applications. An intermediate band structure is introduced by Sm-doping, and empty orbitals in the conductive band are introduced by Na-doping. These factors, combined with the increased local charge density around the Sm and Na atoms, result in an increased electrical conductivity, improved electron mobility, and provide additional electrons for enhancing catalytic reactions. As a consequence, the judicious co-doping of CaBi₂Nb₂O₉ with Sm and Na leads to a unique synergetic piezo-photo-electric effect to provide a superior piezo-photo-catalytic performance for H₂ production (158.53 µmol g⁻¹ h⁻¹) and pollutant degradation (rate constant, k = 0.257 min⁻¹). This new approach provides important insights into the application of defect engineering to exploit the cooperative doping of alkaline earth metals and rare metals to create high-performance catalysts.