Experimental and theoretical investigations on the enhanced photocatalytic performance of titanate nanosheets/sulfur-doped g-C3N4 heterojunction: Synergistic effects and mechanistic studies

Abstract

• Successful fabrication of unique 2D/2D hetero-architecture via in-situ assembly method. • Synergistic effects of different roles of sulfur doping in the enhanced photocatalytic performances of SCN and TNS/SCN. • Distinct difference in Femi levels via the modulation of sulfur doping was evidenced by DFT calculations. • Distinct difference in Femi levels enhanced the electronic coupling and accelerated the interfacial charge transport. • Mechanisms toward the TC-HCl degradation and S-scheme interfacial charge transports were proposed. In this study, novel titanate nanosheets/g-C 3 N 4 (TNS/CN) and titanate nanosheets/sulfur-doped g-C 3 N 4 (TNS/SCN) heterojunctions were successfully fabricated by the in-situ assembly for the efficient removal of tetracycline hydrochloride (TC-HCl). TNS/SCN achieved 1.87, 7.89 and 3.27 times increases in photodegradation performance compared to TNS/CN, TNS and SCN, respectively, due to the collaboration of the unique 2D/2D hetero-architecture, synergistic effects of different roles of sulfur doping in SCN and TNS/SCN, and step-scheme interfacial charge transport. The unique 2D/2D hetero-architecture provided numerous convenient nanochannels for charge transport, while sulfur doping introduced the impurity states and defects in SCN, which contributed to the enhanced visible-light absorption and efficient separation of photo-generated carriers. Besides, sulfur doping induced the distinct difference in Fermi levels and enhanced electronic coupling between TNS and SCN as evidenced by density functional theory calculations and X-ray photoelectron spectra, which facilitated the interfacial charge transport in heterojunction. The accelerated interfacial charge transport in TNS/SCN driven by the enhanced internal electric field promoted the efficient separation of photogenerated carriers. TNS/SCN can achieve excellent stability and reusability after four consecutive cycles, over a wide pH range or under coexisting anion conditions. Mechanisms toward the TC-HCl degradation and step-scheme interfacial charge transport were also proposed. This work provides a new strategy to enhance the catalytic performance of step-scheme heterojunction.