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

Abstract

We propose a potential solution to the problem of severe recombination of photogenerated electron-hole pairs in composite catalysts. The g-C3N5 has better electronic properties and photocatalytic efficiency than g-C3N4, and In2.77S4 is a typically sulfur-deficient sulfide with stable structure and strong visible light absorption. However, the In2.77S4/g-C3N5 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-C3N5 to prepare hybrid material, which subsequently combined with In2.77S4. The high-efficiency S-scheme In2.77S4/NCDs-(g-C3N5) heterojunction was prepared by electrostatic self-assembly to prevent the thermal decomposition of g-C3N5. Photocatalytic experiments show that In2.77S4/NCDs-(g-C3N5) composite has excellent photodegradation efficiency of rhodamine B (94.23 %), high photocatalytic H2 production (7134 μmol·g−1h−1), and good reusability in the visible light. The H2 evolution rate of In2.77S4/NCDs-(g-C3N5) composite is about 30.10, 3.89 and 3.08 folds than In2.77S4, g-C3N5 and In2.77S4/g-C3N5, respectively. The photoluminescence spectroscopy (PL) and the time-resolved fluorescence decay (TRF) indicated a substantial reduction in photogenerated carrier recombination of In2.77S4/NCDs-(g-C3N5) compared to In2.77S4/g-C3N5. 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 In2.77S4/NCDs-(g-C3N5) 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.