Tailored synthesis of size-controlled resorcinol-formaldehyde resins nanospheres towards enhanced photocatalytic activity

Resorcinol-formaldehyde (RF) resins have emerged as promising photocatalysts due to their unique composition of π-conjugated and π-stacked benzenoid-quinoid electron donor-acceptor (D-A) resorcinol pairs. In this study, a series of RF resin nanospheres were synthesized using a high-temperature hydrothermal method. By adjusting the hydrothermal parameters, RF resin spheres with different sizes ranging from 60 nm to 1.2 μm were successfully produced. The size of the RF resin spheres was found to have a significant impact on the photocatalytic activity for the decomposition of Rhodamine B (Rh B), an organic dye. Within a 90-min timeframe, the photodegradation efficiencies achieved were 65 %, 33 %, 21 %, and 11 % for RF resin spheres with different sizes, respectively. Notably, the smallest RF resin spheres exhibited the highest photocatalytic efficiency among the RF resin photocatalysts. This enhanced performance can be attributed to the increased exposure of abundant active sites, facilitated transfer of photogenerated charges to the catalyst surface, and improved adsorption capacity for Rh B through π-π interactions and surface hydrogen bonding networks. Based on the band structure analysis of the RF resin photocatalysts, the active species responsible for the photocatalytic degradation process were identified as hydroxyl radicals (˙OH). These radicals were predominantly generated through the multistep reduction of O2 within the RF resin photocatalysis system under light irradiation. This research provides valuable insights into the design and development of size-controlled D-A type conjugated polymers with improved photocatalytic activity.