Fabricating fragmented intramolecular D-A integrated carbon nitride photocatalyts with elevating activity: Performance and mechanism analysis

Abstract

Carbon nitride (CN) possesses great potential in photocatalytic solar-energy conversion for environmental pollution removal and hydrogen energy generation. However, pristine CN suffers unsatisfactory photocatalytic activity owing to insufficient visible light response, low activity sites exposure, lazy exciton separation and ready carrier recombination. In this work, fragmented intramolecular D-A integrated CN (FBCN) was contracted via a facile m-aminophenylboronic acid doping followed two-step post-processing. The intramolecular D-A integrated structure can strengthen exciton separation and carrier migration driving forces, while the fragmented nanoflakes structure with rich in-plane edges can shorten the migration distance of charge-to-surface in-plane and vertical direction, as well as expose more marginal active sites. The hydrogen evolution rate of optimized 25-FBCN photocatalyst reaches 2545 μmol h−1 g−1, which is 5.2 times higher than that of pristine CN and 1.3 times over the 25-BCN. The 25-FBCN can degrade 87% sulfamethoxazole, and the kinetic rate constant is 3.9 times higher than that of CN. The radical capture and ESR tests reveal stronger radical signals in 25-FBCN degradation system than that of CN. The MS and online FTIR present photodegradation pathway and intermediate, and in-site record functional groups variation during degradation reaction. The SEM/TEM/AFM/XPS/EPR, N2 adsorption-desorption and water contact analysis confirm the generation of smaller-sized nano fragments with rich in-plane edges. The UV–vis DRS/EIS/PCR/PL/TRPL and band structure verify that more effective charge dissociation/migration behavior of 25-FBCN than pure CN. Finally, DFT theoretical calculations and KPFM test further verify the generation of intramolecular D-A integrated structure and clarify the latent propel mechanism of performances.