Giant hydrogen evolution reaction rate induced by ferroelectric polarization in BiFeO3 nanostructures

Integrating ferroelectric materials into photoelectrochemical (PEC) systems is a potentially promising way of improving the efficiency of solar water splitting. Despite the growing interest in ferroelectric materials for PEC applications, achieving effective domain alignment in polycrystalline films remains a significant challenge. Unlike epitaxial or single-crystal systems, polycrystalline ferroelectrics inherently suffer from random grain orientations and intrinsic structural disorder, which limit their polarization efficiency. In this study, we develop nanostructured BiFeO 3 (BFO) photoelectrodes via a low-cost spray-coating technique. We demonstrate that applying an external electric field successfully induces ferroelectric poling across the disordered polycrystalline matrix, resulting in effective dipoles alignment and a significant enhancement in PEC performance. In contrast to reported studies, our work demonstrates that ferroelectric polarization can be effectively harnessed even in undoped, polycrystalline BFO, suggesting that structural limitations associated with grain boundaries and crystallographic disorder can be overcome through external electric field poling. Specifically, polarized BFO photoelectrode with -5V bias exhibited a hydrogen production rate of 7368 μmol L −1 h −1 , which is 9-fold compared to the 813 μmol L −1 h −1 yield obtained by pristine BFO. This superior performance, attributed to the alignment of ferroelectric domains, enabled efficient charge carrier separation and reduced recombination rate. Our findings underscore the beneficial effects of ferroelectric catalysts and promote photoelectrocatalysis beyond conventional semiconductor catalysts and band gap engineering, in particular by using poling as a scalable and reversible process for improving PEC performance. • Calcination controls BFO size and absorption, enhancing PEC efficiency. • Lower calcination temperatures improve optical absorption in BFO. • Poling boosts charge separation, dramatically enhances hydrogen evolution. • Poling is a scalable method to optimize BFO for solar-to-hydrogen conversion.