Dual interfacial build-in electric field effect induced by sandwich-type heterojunction for propelling photocatalytic fuel extraction from CO2 in water

Photocatalytic fuel extraction from CO2 in water driven by solar energy is a sustainable technology with potential applications, but the developing high-efficient photocatalysts is still a challenging issue. Herein, a new sandwich-type polymeric carbon nitride (PCN)-based heterojunction is exploited by embedding Bi12O17Cl2 nanoplates in PCN nanosheet interlayers through a complex series of Bi12O17Cl2 dissolution, ions diffusion and in situ growth on the exfoliated PCN nanosheets, and subsequent self-assembly procedure in a facile hydrothermal process. The fabricated sandwich-type PCN/Bi12O17Cl2/PCN heterojunction significantly enhances the photocatalytic CO2 reduction performance in comparison with Bi12O17Cl2 and PCN. The CO and CH4 yields of the optimal PCN/ Bi12O17Cl2/PCN-3 sample within 4 h are 3.74 and 2.62 times as high as that of PCN, and 8.95 and 6.65 times as high as that of Bi12O17Cl2, respectively. The unique sandwich-type structure of PCN/Bi12O17Cl2/PCN induces dual interfacial build-in electric field effect to effectively impel the spatial charge separation at the interface inside heterojunction, thus boosting photocatalytic performance. This work develops an innovative structure design philosophy of PCN-based heterojunctions applied in photocatalytic CO2 reduction.