Heterostructured PHI‐PTI/Li⁺Cl⁻ Carbon Nitrides for Multiple Photocatalytic Applications

Abstract

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/Li+Cl−) 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.

Rational design of a carbon/potassium poly(heptazine imide) heterojunction for enhanced photocatalytic H2 and H2O2 evolution

“…7,8 Poly(heptazine imide), a new type of highly crystalline carbon nitride, has already stood out among emerging photocatalysts owing to its non-toxic nature, extreme stability, visible-light absorption and suitable energy-level positions that meet the requirements for H 2 and H 2 O 2 evolution. 9,10 Remarkable milestones in maximizing solar-conversion efficiencies of carbon nitrides include a number of effective strategies such as nanostructuring, reducing the stacking distance, defect engineering and introduction of donor–acceptor functionalities. 11–14 Apart from these methods, constructing heterojunctions is a longstanding tool to boost the photoactivity by driving photoexcited electrons and holes toward opposite directions owing to the presence of a built-in electric field.…”

Metal Poly(heptazine imides) as Multifunctional Photocatalysts for Solar Fuel Production

“…[16] A layered polymeric semiconductor-graphitic carbon nitride (g-C 3 N 4 ), has recently gained increasing popularity as an economic and environmental-friendly photocatalyst with controllable chemical and catalytic properties. [17][18][19][20] The notation g-C 3 N 4 indeed represents a wider class of materials composed of triazine or heptazine (tri-s-triazine) units covalently linked together via sp 2 hybridized tertiary N atoms or NH-groups. [21] The adjacent layers are stacked via van der Waals interactions forming a graphitic-like structure.…”

Metal Poly(heptazine imides) as Multifunctional Photocatalysts for Solar Fuel Production

“…[16] A layered polymeric semiconductor-graphitic carbon nitride (g-C 3 N 4 ), has recently gained increasing popularity as an economic and environmental-friendly photocatalyst with controllable chemical and catalytic properties. [17][18][19][20] The notation g-C 3 N 4 indeed represents a wider class of materials composed of triazine or heptazine (tri-s-triazine) units covalently linked together via sp 2 hybridized tertiary N atoms or NH-groups. [21] The adjacent layers are stacked via van der Waals interactions forming a graphitic-like structure.…”