Ultrafast defect passivation enables stable BiFeO3 photocathodes for solar-fuel conversion

Abstract

Developing highly efficient and stable photoelectrodes is crucial for photoelectrochemical (PEC) solar-fuel conversion systems. Bismuth ferrite (BiFeO3, BFO) is a promising photocathode material but suffers from carrier losses and surface photo-corrosion. This study introduces a thermal pulse treatment (TPT) method to optimize BFO films by forming a passivation layer that improves crystallinity and reduces surface oxygen vacancies (VO). As a result, TPT-treated BFO achieved a 2.8× higher photocurrent density, an 84% stability retention after 20 h, a 70% improvement in incident photon-to-current efficiency, and a superior H2O2 production rate compared with untreated BFO. Advanced characterization confirms enhanced crystallinity, reduced grain boundaries, and minimized non-radiative recombination. The electron decay and spatial loss rate calculations further validate TPT's role in mitigating surface charge trapping and improving carrier transport efficiency. This study highlights the effectiveness of TPT in defect passivation, providing a strategy for high-performance PEC materials in solar energy conversion.