Two series of novel carbon nitride photocatalysts, Rho-CN (“rhodizonate-doped carbon nitride”) and Rho-CN-TC (Rho-CN treated in potassium thiocyanate melt), are synthesized in a multistep fashion via copolymerization of cyanamide with potassium rhodizonate. The formed ionic carbon nitrides are composed of poly(triazine imide) (PTI/LiCl) and potassium poly(heptazine imide) (K-PHI) phases and provide a broad absorption range up to 800 nm. The photocatalysts are characterized by several techniques (including diffuse reflectance ultraviolet–visible, powder X-ray diffraction, Fourier transform infrared, scanning electron microscopy, and electrochemical methods) and studied in a series of photocatalytic reactions, including red light-promoted benzylamine oxidation, dual photoredox/nickel C–N cross-coupling, and hydrogen peroxide evolution. The optimal ratio of rhodizonate dopant in its mixture with cyanamide is found to be 0.5 mol%. The performance of the newly synthesized materials is comparable to the activities of the benchmark catalysts K-PHI and CN-OA-m (defective poly(heptazine imide) doped with oxamide), while not requiring more expensive nitrogen sources for preparation, like 5-aminotetrazole, or multiple oven cycles.

This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 861151 Solar2Chem. The material presented and views expressed here are the responsibility of the authors only. The EU Commission takes no responsibility for any use made of the information set out. J.A.S. also thanks the Spanish Ministry of Science and Innovation for a Ramon y Cajal research associate contract (RYC2021-031006-I). A.G. and C.P. would like to thank Dr. Camilo A. Mesa (Institute of Advanced Materials (INAM), Universitat Jaume I (UJI)) for help with impedance data processing. Michael Born (electric workshop of the MPICI) is acknowledged for his contribution to this project. Open Access funding enabled and organized by Projekt DEAL.

Peer reviewed