Enhancing Photocatalytic CO<sub>2</sub> Reduction and Photo-oxidative Coupling over CdS/S-<i>g</i>-C<sub>3</sub>N<sub>4</sub> Heterojunction Interface into Solar Chemicals

Abstract

Graphitic carbon nitride (g-C3N4) has gained attention as a metal-free photocatalyst to generate solar chemicals via efficient solar-driven CO2 reduction reactions. Even though the pristine g-C3N4 and its analogous ones have excellent chemical properties, a disordered structure observed in various types of g-C3N4 hinders the efficient charge separation process as well as the transport of photoexcited charge carriers linked to the photocatalytic performance. To overcome this limitation, we employed the introduction of a heterojunction architecture into sulfur-doped g-C3N4 with CdS. By using the self-assembled method, we fabricated the CdS/S-g-C3N4 heterojunction photocatalyst and designed a hybrid artificial photosynthetic module including a CdS/S-g-C3N4 photocatalyst and biological enzyme for the generation of HCOOH from CO2. From the photocatalytic test, it was confirmed that the presence of the interfacial heterojunction in CdS/S-g-C3N4 showed the enhanced production of formic acid that is much higher than that in the pristine S-g-C3N4. The systematic spectroscopic measurements provide mechanistic insights for the photoinduced electronic dynamics linked to the macroscopic photocatalytic performance in the CdS/S-g-C3N4 heterojunction photocatalyst. Our study suggests that the artificial photosynthesis based on the heterojunction architecture-embedded photocatalyst will offer a promising and sustainable strategy for fixing CO2 and generating solar chemicals.