Embedding In2.77S4 into NCDs-(g-C3N5) hybrid materials to enhance photocatalytic hydrogen production and rhodamine B degradation by constructing electron-highways

We propose a potential solution to the problem of severe recombination of photogenerated electron-hole pairs in composite catalysts. The g-C 3 N 5 has better electronic properties and photocatalytic efficiency than g-C 3 N 4 , and In 2.77 S 4 is a typically sulfur-deficient sulfide with stable structure and strong visible light absorption. However, the In 2.77 S 4 /g-C 3 N 5 composite catalyst has severe recombination of photogenerated electron-hole pairs, which limits its performance. To solve this problem, we introduced NCDs (nitrogen-doped carbon dots) into g-C 3 N 5 to prepare hybrid material, which subsequently combined with In 2.77 S 4 . The high-efficiency S-scheme In 2.77 S 4 /NCDs-(g-C 3 N 5 ) heterojunction was prepared by electrostatic self-assembly to prevent the thermal decomposition of g-C 3 N 5 . Photocatalytic experiments show that In 2.77 S 4 /NCDs-(g-C 3 N 5 ) composite has excellent photodegradation efficiency of rhodamine B (94.23 %), high photocatalytic H 2 production (7134 μmol·g −1 h −1 ), and good reusability in the visible light. The H 2 evolution rate of In 2.77 S 4 /NCDs-(g-C 3 N 5 ) composite is about 30.10, 3.89 and 3.08 folds than In 2.77 S 4 , g-C 3 N 5 and In 2.77 S 4 /g-C 3 N 5 , respectively. The photoluminescence spectroscopy (PL) and the time-resolved fluorescence decay (TRF) indicated a substantial reduction in photogenerated carrier recombination of In 2.77 S 4 /NCDs-(g-C 3 N 5 ) compared to In 2.77 S 4 /g-C 3 N 5 . Taking advantage of the high conductivity of NCDs , the electron-highways were constructed in heterojunctions, which accelerates the interfacial depletion of useless electron-hole pairs and reserved more strong redox carriers. In addition, we inferred a possible energy band structure for In 2.77 S 4 /NCDs-(g-C 3 N 5 ) heterojunction based on the energy band bending theory. This work provides an expandable idea for improving the utilization efficiency of photogenerated carriers by constructing electron-highways in heterojunctions.