Enhanced activity and stability of polymeric carbon nitride photoanodes by yttrium incorporation†

Polymeric carbon nitride materials (CNs) show promising potential as photoanodes in water-splitting photoelectrochemical cells. However, poor catalytic activity at the electrode–water interface limits their performance and longevity, resulting in low photoactivity and unwanted self-oxidation. Here, we demonstrate a high-performance photoanode based on polymeric carbon nitride doped with yttrium clusters, achieving enhanced activity and stability with high faradaic efficiency for water oxidation. Incorporating yttrium clusters enhances light harvesting, electronic conductivity, charge separation, and hole extraction kinetics, enabling efficient water oxidation. Furthermore, the strong interaction between yttrium and the CN's nitrogen groups guides the formation of yttrium-rich one-dimensional tubular structures that interconnect two-dimensional CN sheets. The optimized photoanode delivers a photocurrent density of 275 ± 10 μA cm⁻² with 90% faradaic efficiency for oxygen evolution, demonstrates stable performance for up to 10 hours, and achieves external quantum efficiencies of up to 14% in an alkaline medium.