Simultaneously enhanced photon absorption and charge transport on a distorted graphitic carbon nitride toward visible light photocatalytic activity

Abstract

Abstract The graphitic carbon nitride (g-C3N4) has emerged as one of the most promising candidates to replace the metal oxide-based catalysts for highly efficient photocatalytic materials. However, the intrinsic drawbacks of weak visible-light adsorption and poor charge separation efficiency seriously limit its practical applications. Thus, struggling controls over their structure parameters to optimize the photoelectrical properties on molecular-level for realizing highly active metal-free g-C3N4 photocatalysts have attracted a lot of focuses. Herein, a novel isopropanol assisted solvothermal-copolymerization strategy is rationally designed to synthesize a compact O, S-co-doping g-C3N4 (CNUS) with markedly reinforced π-π* and n-π* electron transitions. The meliorative structure and energy level configuration result in elevated effects for both visible-light (photon) adsorption and photo-induced carries transfer, and the CNUS exhibits outstanding photocatalytic hydrogen evolution and rhodamine B degradation performance under visible light. In addition, after continuously testing, the CNUS still shows superior stability with nearly negligible decay for both photocatalytic reactions. The characterization results indicate that the incorporated oxygen and sulfur engineer the charge, and the layered-stacking distance decreases from 0.328 to 0.322 nm, compared its counterpart (CNU prepared by direct pyrolysis of urea). Importantly, the enriched charge facilitates the rate-limiting separation of photogenerated carriers, and hence improved the visible light photocatalytic efficiency.