Interfacial engineering mediated carriers' dynamics in Cu_2-xS/g-C₃N₄ p-n heterojunctions for efficient CO₂...

Converting CO₂ into solar fuels via photocatalysis represents a promising strategy for advancing toward carbon neutrality. Nevertheless, the efficiency of this process is frequently hindered by the rapid recombination of photoexcited charge carriers. Herein, we fabricated a Cu_2-xS/g-C₃N₄ (CS/CN) p-n heterojunction with closely-contacted heterojunction interface for CO₂ photoreduction. The results of photoelectrochemical tests and transient absorption spectra indicated the p-n heterojunction between CS and CN generated a robust built-in electric field, which promoted unidirectional transport of electrons from CS to CN and holes from CN to CS, thereby accelerating the spatial separation of photogenerated carriers. Both theoretical and experimental studies demonstrated that the addition of Cu_2-xS not only intensified the interaction between CN and CO₂, but also significantly promoted the adsorption and subsequent activation of CO₂ molecules, and reduced the formation energy barrier of intermediate *COOH from 1.09 to 0.42 eV during CO₂ reduction. As a result, the CS/CN p-n heterojunction exhibited an average CO yield of 67.4 μmol g^-1. This work reveals the dual roles of p-n heterojunctions in simultaneously addressing the limitations of bulk charge transport and tailoring the surface catalytic environment, establishing a general framework for the design of p-n heterojunctions.