S-scheme-Mediated Ce-NSO/Ce-gCN Heterostructure for Enhanced Photocatalytic Hydrogen Evolution via Seawater Splitting

Abstract

Developing stable and cost-effective photocatalysts that operate without precious metals or sacrificial agents is essential for practical and sustainable hydrogen production. In this study, a rare-earth cerium-doped S-scheme heterostructure was rationally designed and synthesized to achieve enhanced photocatalytic hydrogen evolution from simulated seawater without using any external hole scavengers. The direct use of seawater for the photocatalytic hydrogen evolution is highly desirable because it constitutes nearly 97% of the Earth's water resources and eliminates the energyintensive purification steps required for deionized water, thereby offering a more sustainable and economically viable pathway for large-scale hydrogen production. The incorporation of Ce in both NiSnO3 (NSO) and graphitic carbon nitride (gCN) significantly improved interfacial coupling between NSO and gCN, charge carrier separation, and light-harvesting capability. Structural, optical, and photoelectrochemical studies confirmed an efficient S-scheme charge transfer mechanism. The 4% (w/w) Ce-doped photocatalyst delivered a hydrogen evolution rate of 1510 µmol.(g.h) -1 , which is twice the value of NSO/gCN and six times that of gCN, demonstrating the strong synergistic effects of heterojunction design with Cedoping. Radical trapping test and the EPR and XPS analysis further attributed the enhanced activity to the generation of reductive electrons with prolonged carrier lifetime. The Ce-NSO/Ce-gCN composite also exhibited an excellent stability with minimal activity loss over multiple cycles. These findings demonstrate that rare-earth doping is a key strategy for optimizing both the efficiency and durability of S-scheme heterostructures, offering a promising route towards sustainable photocatalytic hydrogen production from plentiful seawater resources.