Design of S-scheme heterojunction catalyst based on structural defects for photocatalytic oxidative desulfurization application

• Highly visible light-responsive Ag 3 PO 4 /d-C 3 N 4 composites were prepared. • The photocatalyst exhibited excellent photocatalytic activity for Dibenzothiophene. • The defective carbon nitride improves light absorption and charges separation. • The construction of Z-scheme heterojunctions promoted the photocatalytic activity. • The mechanism of photocatalytic oxidative desulfurization was investigated. Carbon nitride (g-C 3 N 4 ) is promising for many applications, but its photocatalytic activity is limited by weak visible light absorption and photogenerated carrier complexes. Herein, the thermally defective carbon nitride (d-C 3 N 4 ) has a larger specific surface area and more reactive sites. d-C 3 N 4 helped Ag 3 PO 4 nanoparticles to be uniformly deposited on the surface of it and made it easier for particle dispersion. d-C 3 N 4 and Ag 3 PO 4 form an S-scheme heterojunction, facilitating the transfer and separation of photogenerated electrons and holes, and possessing high redox ability, which results in improved photocatalytic performance. The experimental results showed that the conversion of 10 : 1 Ag 3 PO 4 /d-C 3 N 4 for photocatalytic oxidative desulfurization (PODS) under visible light was as high as 92.5 % at 3 h, mainly due to the S-scheme heterojunction further promoting the transfer and separation of photogenerated carriers, suppressing the fast complexation and improving the efficiency of photocatalysis. In addition, the conversion mechanism of PODS was demonstrated using radical capture test, electron paramagnetic resonance spectrometer (EPR), and gas chromatography-mass spectrometry (GC-MS). This study helps researchers to understand the S-scheme heterojunctions constructed based on defects and provides new ideas for the design and application of photocatalysts.