One-step construction of S-scheme heterojunctions of N-doped MoS2 and S-doped g-C3N4 for enhanced photocatalytic hydrogen evolution

Step-scheme (S-scheme) heterojunctions of S-doped g-C3N4 (SCN) and N-doped MoS2 (NMS) were constructed by a one-step thermal polycondensation method in Ar atmosphere using thiourea and ammonium tetrathiomolybdate as starting materials. X-ray photoelectron spectra revealed the formation of new N-Mo and C-S-Mo bonds between SCN and NMS and enhanced NMS purity. The as-prepared NMS/SCN with an NMS ratio of 19.3 wt% showed the highest photocatalytic activity. Within 4 h of illumination, its H2 generation rate reached 658.5 μmol/g/h, which was about 23 and 38 times higher than that of pure SCN (28.8 μmol/g/h) and NMS (17.4 μmol/g/h), respectively. UV–vis diffuse reflectance spectra (DRS), surface photovoltage spectrum (SPV), photoluminescence (PL) spectra and electrochemical tests revealed the extended visible light absorption and enhanced photo-generated carrier separation of the formed S-scheme heterojunction. The mechanism and driving force of charge transfer and separation in S-scheme heterojunction photocatalysts are investigated and discussed.