Atmosphere engineering of metal-free Te/C3N4 p-n heterojunction for nearly 100% photocatalytic converting CO2 to CO

Abstract

Carbon nitride (CN)-based heterojunction photocatalysts hold promise for efficient carbon dioxide (CO₂) reduction. However, suboptimal production yields and limited selectivity in CO₂ conversion pose significant barriers to achieving efficient CO₂ conversion. Here, we present the construction of a p-n heterojunction between ultrasmall Te NPs and CN nanosheet using a novel tandem hydrothermal-calcination synthesis strategy. Through ammonia-assisted calcination, ultrasmall Te NPs are grown in-situ on the CN nanosheets’ surface, resulting in the generation of a robust p-n heterojunction. The synthesized heterojunction exhibits increased specific surface area, reinforced visible light absorption, intensive CO₂ adsorption capacity, and efficient charge transfer. The optimum Te/CN-NH₃ demonstrates superior photocatalytic CO₂ reduction activity and durability, with nearly 100 ​% selectivity for CO and a yield as high as 92.0 ​μmol ​g⁻¹ ​h⁻¹, a fourfold increase compared to pure CN. Experimental and theoretical calculations unravel that the strong built-in electric field of the Te/CN-NH₃ p-n heterojunction accelerates the migration of photogenerated electrons from Te NPs to the N site on CN nanosheets, thereby promoting CO₂ reduction. This study provides a promising material design approach for the construction of high-performance p-n heterojunction photocatalysts.