One of the primary challenges posed by global warming pertains to the imperative transition from fossil fuel dependency to environmentally sustainable alternatives. Given that electricity alone cannot suffice for all existing applications, the exploration of high-density energy molecules as viable substitutes becomes crucial. Among these, hydrogen stands out as a promising contender. Presently, the predominant method of hydrogen production revolves around steam reforming of natural gas. However, the global objective is to implement a method for generating green hydrogen to support sustainable processes.[1]

Electrolysis employing renewable energy sources represents a modern way for realizing green hydrogen production. Concurrently, another compelling prospect that has gained significant traction in recent years is photocatalysis. This innovative approach involves catalytic water splitting (overall water splitting) or the use of a sacrificial reagent (hydrogen evolution) to directly synthesize hydrogen via solar energy conversion.[2] Notably, carbon nitride has emerged as a particularly promising photocatalyst for such reactions, owed to its favorable cost-effectiveness, chemical resilience, and absorption capabilities within the visible solar spectrum.[3]

Nonetheless, a notable limitation arises from our recent work,[4] which has illustrated the phenomenon of photo self-degradation within defect-rich graphitic carbon nitride containing heptazine units. To preserve the advantages while augmenting stability, a crystalline carbon nitride containing lithium cations and chloride anions, primarily composed of triazine units, has been synthesized by the research group of Maggard.[5]

We will present a comparison of photostability and catalytic activity in relation to conventional graphitic carbon nitrides. Ion chromatography studies show a significantly elevated stability of the crystalline carbon nitride structure. To address recombination reactions, an introduced co-catalyst in the form of pyrite (FeS₂) with 1, 5, and 10 wt% loading has been implemented. The addition of this co-catalyst has yielded increased activity for both carbon nitride variations. While the graphitic carbon nitride persists in facing challenges of self-degradation, the crystalline phase maintains its stability in the presence of the co-catalyst.