Electrostatic Self-Assembly-Driven Heterojunction of Cubic CeO₂/g-C₃N₄ Nanosheets for Efficient Photocatalytic Hydrogen Evolution and Photoelectrocatalytic Water Splitting: A Hybrid Experimental and Theoretical Study

Nanohybrid catalysts hold great promise for photocatalysis and photoelectrocatalysis, with significant progress still to be made. We synthesize a graphitic carbon nitride (GCN)-CeO₂ heterojunction via electrostatic self-assembly. Characterization confirms that CeO₂ nanocubes are uniformly anchored onto layered GCN, forming a high-quality interface with abundant active sites. This architecture facilitates efficient separation of photogenerated charge carriers and an improved optical response, as further supported by density functional theory and finite-difference time-domain simulations, which reveal a modified band structure and optical response at the type-II heterojunction interface. The resulting hybrid exhibits excellent water splitting performance, with a photocurrent density of 5.70 mA cm^-2 at a low onset potential of 0.43 V vs Ag/AgCl. The GCN-CeO₂ photocatalyst shows an enhanced hydrogen evolution rate of 809.23 μmol g^-1 h^-1, which is 6.7 times higher than that of pure CeO₂ and 3.2 times higher than that of the GCN photocatalyst. The reported findings highlight the promising potential of electrostatic self-assembly as an effective strategy for the development of efficient catalysts for solar fuel production.