Na-Doped Graphitic Carbon Nitride for Removal of Aqueous Contaminants via Adsorption and Photodegradation

Graphitic carbon nitride (g-CN) has gained significant popularity as a visible-light-activated photocatalyst in energy and environmental applications. Most papers are dedicated to improving its photocatalytic performance; however, an investigation of its adsorption performance not only expands its application scope but also provides insight into its surface interactions. Herein, sodium-doped g-CN (Na(x)-CN) is synthesized via one-step pyrolysis of the mixture of melamine and sodium carbonate (Na2CO3). The prepared Na(x)-CN not only demonstrates superior adsorption capacities (maximum adsorption capacity of methylene blue up to 1319 mg/g, which is ∼650 times higher than that of the pristine g-CN) but also overcomes the lack of selectivity and slow adsorption kinetics of commonly used adsorbents. The extraordinary adsorption capacities are mainly attributed to π–π interactions and electrostatic interactions. Moreover, the Na2CO3-assisted synthesis route improved the optical properties and photocarrier separation efficiency, which are beneficial for further removal of contaminants via photodegradation. This work introduces a facile route for mass production of Na-doped g-CN with excellent adsorption capacities and selectivity as well as enhanced photocatalytic performance.