The Haber-Bosch process has delivered significant global benefits, like establishing ammonia as fertilizer compound and moreover as platform chemical. Its dependence on fossil fuels accounts for approximately 2 % of world´s energy consumption, is the biggest disadvantage of this process. This leads to extensive research into alternative methods. Photo-/ electrocatalytical nitrogen reduction, stands out as a promising approach due to its compatibility with renewable energy sources and the possibility to work under ambient contitions.¹ Since also scalability is possible, this offers decentralized production of ammonia containing products.²

Carbon nitrides, like C₃N₄, are known for their low density, high thermal and high chemical stability, making them useful in areas like gas storage, photo- /electro catalysis, and sensors.³ Their catalytic efficiency is limited by the fast recombination of photo generated charges and small surface areas.⁴

To improve these materials, adding metal centers and adjusting the carbon-to-nitrogen (C/N) ratio are promising ways. Modifying the C/N ratio influences the light absorption range without adding impurities. C₃N₅ builds on the heptazine structure of C₃N₄, increasing electron density and thus improving light absorption. Due to the heptazine modification the chemical properties of carbon nitrides compounds changes, related to the added electron lone pair at the additional nitrogen atom.⁵

In addition to the unique properties of C₃N₅, carbon nitrides can also serve as a platform for active metal centers,⁶ these enhance the electronic structure and charge dynamics.³ Vanadium inhibits hydrogen production while carbon nitrides are suitable for hydrogen generation. Since the HER is inhibited, vanadium-doped carbon nitride becomes more suitable for NRR applications for which HER is a unwanted side reaction.

In this study, a synthesis method was developed to modify C₃N₅ with very high vanadium concentrations. For this synthesis, the exchange with the air atmosphere was minimized not only by covering with a lid but also by manually sealing the whole crucible, still allowing pressure equalization. This approach allows the incorporation of vanadium at concentrations of up to 10 wt.% into the structure without the formation of vanadium oxide or significant alterations to the carbon nitride structure of C₃N₅. The resulting structures were compared to powders produced under inert gas conditions. Frist qualitative measurements indicate the electrochemical activity and stability for vanadium doped C₃N₅ materials.