Controlled Synthesis of Nitro-Terminated Poly[2-(3-thienyl)-ethanol]/g-C3N4 Nanosheet Heterojunctions for Efficient Visible-Light Photocatalytic Hydrogen Evolution

Abstract

Exploration of closely contacted polymeric nanoheterojunctions with suitable frontier molecular orbital energy levels is highly desired for promoting the carrier separation and further improving the photocatalytic performance. In our work, poly[2-(3-thienyl)ethanol]/g-C₃N₄ (PTEtOH/g-C₃N₄) nanosheet heterojunctions were successfully fabricated using a controlled surface hydroxyl-induced assembly process and displayed obviously improved visible-light performance for H₂ evolution. As verified by time-resolved photoluminescence spectra, surface photovoltage spectra and •OH amount measurements, the improved performance is due to the promoted photogenerated carrier transfer and separation in the synthesized PTEtOH/g-C₃N₄ heterojunction with strengthened interface contacts via hydrogen bonding. Furthermore, single-wavelength photocurrent action spectra were performed to confirm that the promoted photogenerated carrier separation is mainly dependent on the excited high-level electron transfer from g-C₃N₄ to PTEtOH. Interestingly, the photocatalytic performance is further improved by synthesizing nitro-terminated PTEtOH (N-PTEtOH) with lowered LUMO energy level and decreased particle size and then constructing N-PTEtOH/g-C₃N₄ nanosheet heterojunction, exhibiting a factor-of-15 enhancement, in comparison with that of g-C₃N₄ and obvious superiority to reported photoactivities. Noteworthily, abundant hydroxyl groups on the surface of the heterojunctions are beneficial for the uniform deposition of Pt nanoparticles as co-catalysts and hence for photocatalytic reactions. This study offers a feasible strategy to design efficient polymeric heterojunctions as nanophotocatalysts for solar-light-driven energy production.