Simultaneous dopants and defects synergistically modulate the band structure of CN in Z-scheme heterojunctional photocatalysts for simultaneous HER and OER production

Enhancing solar-driven oxygen evolution reactions (OER) and hydrogen evolution reactions (HER) is critical for advancing renewable energy solutions and mitigating global CO₂ emissions. In this study, we employed a blend of experimental and theoretical approaches to improve the properties of graphitic carbon nitride (CN). This improvement entailed the introduction of isolated boron dopants and nitrogen deficiency into CN, achieved via a straightforward calcination process with sodium borohydride, followed by the integration of ultrathin iron phthalocyanine (FePc) connected through phosphate groups. The synthesized nanocomposite, FePc/P–BCNN, exhibited exceptional photocatalytic efficacy in OER and HER, reaching production rates of 915.4 μmol h⁻¹ and 99.5 μmol h⁻¹, marking a substantial enhancement-nearly 8- & 9-fold over traditional CN materials under visible light. This remarkable efficiency stems from a deliberate modification of the conduction and valence bands through the incorporation of B-dopants and N-defects, thereby fine-tuning the band structure for improved OER and HER performance. Furthermore, the potential of ultrathin metal phthalocyanine structures, offering multiple single-atom active sites, and showcased a sustainable approach for photocatalytic OER and HER. The rapid charge separation, propelled by a Z-scheme charge transfer mechanism, facilitated through a dimensionally matched strategy contributes novel insights into the field of sustainable energy conversion technologies.