High-crystalline g-C3N4/BiOIO3 S-scheme heterojunction for efficient photocatalytic CO2 reduction

Photocatalytic conversion of CO 2 into chemical fuels represents a promising route toward achieving carbon neutrality. However, its practical large-scale deployment is severely hampered, primarily due to high charge-transfer resistance and sluggish kinetics. Herein, a high-crystalline g-C 3 N 4 /BiOIO 3 (CCN/BIO) S-scheme is constructed through a one-step KI molten salt method, which offers a greener and simpler alternative to conventional systems while enhancing the crystallinity of CCN and enabling the in-situ deposition of BIO. Benefiting from the high lattice matching between the two components, robust N–O–Bi interfacial chemical bonds are formed, serving as efficient channels for charge migration. As a result, the optimized CCN/BIO composite exhibits a markedly enhanced activity of photocatalytic reduction of CO 2 , with the total yield of CO and CH 4 reaching 4.9 and 3.2 times those of pristine BIO and CCN, respectively. Combined density functional theory (DFT) calculations, in-situ irradiated X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) analyses systematically verify the S-scheme charge transfer pathway, which is synergistically driven by the internal electric field and interfacial chemical bonds. This work provides new insights into the rational design of visible-light-responsive S-scheme heterojunction photocatalysts.