Band Gap Reduction in Lead Bismuth Niobate: Impact of Cerium Substitution in Aurivillius-type Structures on Photocatalytic Activity

Abstract

Developing efficient photocatalysts for environmental remediation remains a critical challenge, especially for degrading toxic organic pollutants. Aurivillius oxides are promising candidates due to their layered structures and chemical tunability. However, strategies to optimize their photocatalytic activity require further exploration. Here, we demonstrate that aliovalent Ce substitution in PbBi₂Nb₂O₉ (PBNO) significantly enhances its photocatalytic performance. The optimized 20 mol% Ce composition shows a 2.6-fold increase in methylene blue degradation efficiency compared to pristine PBNO. Experimental characterizations and first-principles calculations reveal that Ce incorporation induces coupled cation substitution—Ce replaces Pb, and the displaced Pb partially occupies Bi sites. This redistribution modifies the electronic structure by reducing the band gap, introducing Ce³⁺/Ce⁴⁺ redox centers, and improving charge separation. Free radical quenching experiments and band alignment analysis further elucidate the degradation mechanism. This study provides insights into cation substitution in Aurivillius oxides and highlights a promising strategy for designing photocatalysts for water purification.