Photogenerated charge behavior of BiOI/g-C3N4 photocatalyst in photoreduction of Cr (VI): A novel understanding for high-performance

Abstract Z-scheme photocatalytic system was considered as a promising strategy to tackle environmental pollution crises. However, photogenerated charges behaviors of Z-scheme photocatalyst were still ambiguous, particularly for charge-recombination process occurring at the interface of Z-scheme heterojunctions. In this work, a solid-state heterojunction photocatalyst consisting of BiOI and g-C3N4 was fabricated to reveal the Z-scheme transfer process of photogenerated charge. The morphology, physical and optical properties were characterized in detail. The as-prepared BiOI/g-C3N4 composites exhibited higher reduction efficiency of Cr(VI) than that of pure BiOI and g-C3N4, and 79.2% of Cr(VI) removal was achieved after 15 min visible light irradiation (λ > 420 nm). The remarkable degradation performance was due to efficient separation and transfer of photogenerated charge in a direct Z-scheme path. More importantly, the non-radiative recombination process of photoinduced carriers occurring at the interface between BiOI and g-C3N4 was confirmed by the photoluminescence (PL), photoacoustics (PA) spectroscopy, work function (WF) and electron spin-resonance spectroscopy (ESR) measurement. This work shows that appropriate increasing the non-radiative recombination center may help to improve the charge recombination occurring at the interface so as to enhance photocatalytic degradation activity of Z-scheme photocatalytic system.