Exciton-Mediated Energy Transfer in Heterojunction Enables Infrared Light Photocatalysis.

Infrared light accounts for almost half energy of the sunlight, while it is still a huge challenge to efficiently utilize the long wavelength light. Although a few semiconductors can directly absorb infrared light, their intrinsic properties like improper band-edge position and strong electron-hole interaction restrict further photocatalytic applications. Herein, we propose an exciton-mediated energy transfer strategy for realizing efficient infrared light response in heterostructures. Taking black phosphorous/polymeric carbon nitride (BP/CN) heterojunction as an example, we show that CN could be indirectly excited by infrared light with the aid of nonradiatively exciton-based energy transfer from BP. At the same time, excitons are dissociated into free charge carriers at the interface of BP/CN heterojunction, followed by hole injection to BP and electron retainment in CN. As a result of these unique photoexcitation processes, BP/CN heterojunction exhibits promoted conversion rate and selectivity in amine-amine oxidative coupling reaction even under infrared light. This study opens a new way for the design of efficient infrared light activating photocatalysts.