Nanoengineered Au–carbon nitride interfaces enhance photocatalytic pure water splitting to hydrogen

Abstract

Photocatalytic pure water splitting using solar energy is one of the promising routes to produce sustainable green hydrogen (H₂). Tuning the interfacial active site density at catalytic heterojunctions and better light management are imperative to steer the structure–activity correlations to enhance the photoefficiency of nanocomposite photocatalysts. Herein, we report the decoration of nitrogen defect-rich carbon nitride CN(T) with metallic Au nanostructures of different morphologies and sizes to investigate their influence on the photocatalytic hydrogen evolution reaction (HER). The CN(T)-7-NP nano-heterostructure comprising Au nanoparticles (NPs) of ∼7 nm and thiourea-derived defective CN, exhibits an excellent H₂ production rate of 76.8 μmol g⁻¹ h⁻¹ from pure water under simulated AM 1.5 solar irradiation. In contrast to large-size Au nanorods, the high activity of CN(T)-7-NP was attributed to their strong localized surface plasmon resonance (LSPR) mediated visible light absorption and interfacial charge separation. The surface ligands used to control Au nanostructure morphology were found to play a major role in the stabilization of NPs and improve interfacial charge transport between Au NPs and CN(T). First-principles calculations revealed that defects in CN and Au–CN interfacial sites in these nanocomposites facilitate the separation of e⁻/h⁺ pairs after light excitation and provide lower energy barrier pathways for H₂ production by photocatalytic water splitting.