Graphene Oxide as Novel Visible Light Active Photocatalyst: Synthesis, Modification by Nitrogen and Boron Doping, and Photocatalytic Application

Graphene oxide (GO) has become one of the emerging and important sole photocatalyst nanomaterials in recent years due to its exceptional/tunable optoelectronic properties, multifunctionality, and eco-friendly nature. However, challenges remain in tuning surface chemistry, tailoring the band gap, developing doping strategies, and understanding the sole photocatalytic mechanism. This contribution investigated the synthesis of GO via the improved Hummers method by varying the ratio of the oxidizing agents (K2Cr2O7:KMnO4), as well as modifications by nitrogen (N) and boron (B) doping in view of its applications in photocatalytic degradation of organic dye pollutants. Furthermore, changes in surface chemistry, optical, compositional, morphological, and structural properties are investigated to understand the photocatalytic mechanism. The synthesized GO showed a broad spectrum of light absorption with a tunable band gap of 2.4-4.3 eV and exhibited more than 91% degradation of methylene blue dye under direct sunlight. However, the photocatalytic activity decreased after N and B doping attributed to reduced oxygen-containing functional groups, low surface area, and dopants-induced bonding configurations within the GO structure. This study provides a new insight into replacing metallic semiconductor photocatalysts with highly affordable, environmentally friendly, and potent metal-free GO photocatalysts. This study reports on novel graphene oxide (GO) as a stand-alone visible light active photocatalyst, synthesized via improved Hummer's method. It exhibits a larger surface area, hydrophilic nature, and many negatively charged oxygen-containing functional groups serve as active sites for the adsorption of dye molecules which enhance the photocatalytic activity under sunlight. Further, the effects of N and B doping on the photocatalytic activity of GO and its underlying mechanism have been discussed. image (c) 2024 WILEY-VCH GmbH