Band Engineering of BiFeO3 Nanosheet for Boosting Hydrogen Evolution by Synergetic Piezo-photocatalysis

Hydrogen (H2) production through water splitting using sustainable energy sources is gaining increasing attention. However, limited catalytic performance based on a single driving force presents both opportunities and challenges for achieving a high-efficiency H2 output. Exploring multiple driving sources to enhance the comprehensive catalytic performance shows great promise. BiFeO3 (BFO), with features of narrow band gap and ultrahigh ferroelectric polarizations, is considered as a promising alternative candidate for green H2 production from water splitting. However, the inherent overpositive conduction band edge restricts its applications. Therefore, a strategy involving band engineering through heteroatom Co-doping (Cox-BFO) has been proposed to boost piezo-photocatalytic H2 evolution performance. Based on the synergetic effects of the polarization field induced by piezoelectric Co1.8-BFO, suppressed recombination of charge carriers, prolonged charge carrier lifetime, modulated band alignment, and lowered energy barrier for surface H2O adsorption/activation/reduction, the Co1.8-BFO nanosheets exhibit significant piezo-photocatalytic activities with an enhanced H2 generation rate (321.9 μmol·g–1·h–1). That rate is much higher than those of piezocatalytic (127 μmol·g–1·h–1) and photocatalytic (163 μmol·g–1·h–1) performances alone. This work provides an effective approach to advancing the BFO water splitting performance through band engineering.