Construction of a composite photocatalyst with significantly enhanced photocatalytic performance through combination of homo-junction with hetero-junction

Abstract

Twinned BiPO₄ has been confirmed to exhibit higher performance than pristine single-phase BiPO₄ (HBIP) owing to the formation of a homo-junction between monazite monoclinic BiPO₄ (nMBIP) and monoclinic BiPO₄ (mMBIP). In the present study, further promotion of photocatalytic activity of twinned BiPO₄ was achieved by coupling with BiOCl because of the formation of multi-junctions with a ladder band structure. The results showed that the photocatalytic activity of twinned BiPO₄ enhanced 8.7 times and 2.5 times compared to that of pristine BiPO₄ for degradation of methyl orange (MO) and acetaminophen (ACE), respectively, while the photocatalytic activity of the obtained multi-junctioned sample enhanced 35.7 times and 59.5 times compared to that of twinned BiPO₄ for degradation of MO and ACE, respectively. XRD and Raman spectra revealed that the composites exhibited characteristic peaks of BiOCl and BiPO₄ including nMBIP and mMBIP. In addition to the homo-junction between nMBIP and mMBIP, the hetero-junction between twinned BiPO₄ and BiOCl was verified in the composites by TEM and HRTEM. The boosted transfer and separation of photo-excited charge carriers were attributed to the synergy between the homo-junction and hetero-junction in the composite, which were measured by the transient photocurrent response, EIS and PL. Consequently, the corresponding photocatalytic performance was notably improved. This work provides a new concept to design new multi-junctioned photocatalysts with both homo- and hetero-junctions for efficient pollutant removal in environmental renovation.