Optimizing interfacial electric fields in carbon nitride nanosheet/spherical conjugated polymer S-scheme heterojunction for hydrogen evolution

Designing heterojunctions based on carbon nitride offers a promising pathway for enhancing photocatalytic efficiency. This study develops an all-organic S-scheme metal-free heterojunction uniquely composed of carbon nitride nanosheets (GCNNS) and a donor–acceptor conjugated polymer, poly p-aminobenzylidene-so-aniline (PASO), synthesized through a simple yet effective ball-milling technique. This heterojunction demonstrates excellent photocatalytic efficiency for hydrogen (H₂) evolution. The optimized GCNNS/PASO-10 sample attains an H₂ evolution rate of 10.12 ​mmol·g⁻¹·h⁻¹, which is about 5.9 times and 19.5 times greater than those of pure GCNNS and PASO, respectively. This improvement is due to the unique interfacial bonding, increased visible-light absorption, and efficient charge carrier separation facilitated by a strong internal electric field within the S-scheme. Theoretical calculations and characterization reveal that this heterojunction's S-scheme mechanism optimally aligns energy bands and promotes spatial charge separation, driving superior photocatalytic activity. This work presents the unique advantage of all-organic materials for heterojunction construction and provides insights into designing advanced S-scheme systems for sustainable energy conversion.