Control interfacial charge transfer behavior by creating surface defects on structure unit of heterojunction to drive...

Controlling interfacial charge transfer behavior of heterojunction is an arduous issue to efficiently drive separation of photogenerated carriers for improving the photocatalytic activity. Herein, the interface charge transfer behavior is effectively controlled by fabricating an unparalleled V_O-NiWO₄/PCN heterojunction that is prepared by encapsulating NiWO₄ nanoparticles rich in surface oxygen vacancies (V_O-NiWO₄) in the mesoporous polymeric carbon nitride (PCN) nanosheets. Experimental and theoretical investigations show that, differing with the traditional p-n junction, the direction of built-in electric field between p-type NiWO₄ and n-type PCN is reversed interestingly. The strongly codirectional built-in electric field is also produced between the surface defect region and inside of V_O-NiWO₄ besides in the space charge region, the dual drive effect of which forcefully propels interface charge transfer through triggering Z-Scheme mechanism, thus significantly improving the separation efficiency of photogenerated carriers. Moreover, the unique mesoporous encapsulation structure of V_O-NiWO₄/PCN heterostructure can not only afford the confinement effect to improve the reaction kinetics and specificity in the CO₂ reduction to CO, but also significantly reduce mass transfer resistance of molecular diffusion towards the reaction sites. Therefore, the V_O-NiWO₄/PCN heterostructure demonstrates the preeminent activity, stability and reusability for photocatalytic CO₂ reduction to CO reaction. The average evolution rate of CO over the optimal 10 %-V_O-NiWO₄/PCN composite reaches around 2.5 and 1.8 times higher than that of individual PCN and V_O-NiWO₄, respectively. This work contributes a fresh design approach of interface structure in the heterojunction to control charge transfer behaviors and thus improve the photocatalytic performance.