Spectral overlap integral and photon flux-guided design of Pd@CeO 2 nanostructures for efficient solar photocatalysis

Abstract Metal–oxide core–shell nanostructures offer a promising route for coupling plasmonic absorption with catalytic oxide functionality; however, a predictive and quantitative framework linking geometry to solar‐photon harvesting in Pd-based systems remains lacking. Here, we present a systematic finite-difference time-domain investigation of Pd@CeO 2 nanoparticles that explicitly correlates core radius ( r ) and shell thickness ( t ) with hybrid-mode formation, near-field redistribution, and solar harvesting metrics. We show that electromagnetic coupling between the Pd core and the high-index CeO 2 shell produces two distinct hybrid resonances—a UV antibonding mode and a broadband visible bonding mode—whose spectral position, intensity, and energy localization can be continuously engineered through geometric control. By integrating the spectral overlap integral and absorbed photon flux (APF) under AM1.5 G illumination, we establish a quantitative design map demonstrating a clear cubic scaling of solar-photon utilization with both r and t . Importantly, our results reveal that the CeO 2 shell functions as an active electromagnetic mediator, enhancing field penetration and concentrating optical energy directly within the reactive oxide region rather than merely serving as a passive protective layer. This work moves beyond qualitative spectral analysis by providing geometry-dependent, performance-based design rules for maximizing APF and solar energy deposition in Pd-based hybrids, offering a predictive pathway toward rationally engineered plasmon-enhanced photocatalysts for solar-to-chemical energy conversion.