g-C3N4 coupled with GO accelerates carrier separation via high conductivity for photocatalytic MB degradation

Graphitic carbon nitride (g-C 3 N 4 ) is widely utilized in photocatalysis due to its responsiveness to visible light, low cost, and non-toxicity. However, its efficiency is limited by factors such as the rapid recombination of photogenerated electron-hole pairs, slow electron transfer rates, and a limited number of active surface sites. In this study, g-C 3 N 4 was synthesized through thermal polymerization, and varying amounts of graphene oxide (GO) were incorporated via physical blending to fabricate composite photocatalysts. The results indicated that the incorporation of GO not only increased the specific surface area and modified the pore size distribution of g-C 3 N 4 but also affected the heptazine ring structure through chemical bonding, thereby enhancing the density of active sites. Photocatalytic degradation experiments with methylene blue (MB) indicated that g-C 3 N 4 containing 2 % GO exhibited photocatalytic activity 2.84 times greater than that of pristine g-C 3 N 4 . Kinetic simulations indicated that the K app value for the 2 % GO-g-C 3 N 4 composite was 0.00469 min −1 , which is 4.34 times higher than that of pure g-C 3 N 4 (0.00108 min −1 ). Furthermore, this composite maintained high photocatalytic activity after four cycles of reuse. An analysis of the photocatalytic degradation mechanism revealed that the incorporation of GO effectively promoted the separation and transfer of photogenerated electron-hole pairs, enhanced photocurrent density, and improved carrier separation efficiency. Electron spin resonance (ESR) and free radical scavenging experiments confirmed that the primary active species involved in the degradation of MB by the composite photocatalyst were ·O 2 - and h + . This study presents a novel approach for enhancing the photocatalytic performance of g-C 3 N 4 by modifying its electronic structure and surface properties.