Methylated precursor leads to carbon nitride (CNx) with improved interfacial interactions for enhanced photocatalytic performance

Abstract

The utilization of carbon nitride (CN_x) as a benchmark organic photocatalyst for various solar energy conversion reactions has gained traction amongst the catalysis community in recent times. This has been occasioned by the facile synthesis of CN_x coupled with its visible light photocatalytic performance and good stability. However, a persistent limitation of the application of CN_x in solution-based photocatalytic reactions is poor interfacial interactions with substrate or sacrificial agents as a result of poor dispersibility. Using a copolymerization approach, we synthesize CN_x materials with hydrophilic surface groups by calcining a mixture of melamine and methylated melamine salts (Mel_meth) at 550 °C for 4 hours. The resulting modified CN_x materials are water-dispersible and show red shifts in their absorption onsets and photoluminescence (PL) maxima. Compared with benchmark CN_x, the modified CN_x materials show broadening in their XRD peaks, suggesting more disordered and amorphous materials. We demonstrate some distinctions in the charge carrier dynamics between the modified CN_x materials and the benchmark CN_x by acquiring and analyzing their transient absorption spectroscopy (TAS) data. We investigate the photoactivity of the synthesized materials towards hydrogen evolution reaction (HER) and Rhodamine B dye degradation using a visible 405 nm LED light source. The apparent quantum yield (AQY) and dye degradation efficiency are improved for all modified samples compared to benchmark CN_x. We attribute the promising photoactivity of the modified samples to better interfacial interactions with other species within the aqueous environment. Overall, we believe this work may shed light on a general strategy for designing organic polymer photocatalysts with desired surface properties for targeted applications.