Murray-inspired hierarchical hollow Cu/TiO₂ catalysts as a silver lining for plasma-assisted CO₂ conversion: coupling cavity-shell matching with local discharge activation.

Non-thermal plasma(NTP)-assisted CO₂ conversion enables molecular activation under mild conditions, yet its efficiency is still constrained by the coupled limitations of active-species transport, local discharge distribution, and interfacial utilization. Current designs of plasma catalysts mainly focus on active sites, defect engineering, and metal-support interactions, whereas the role of catalyst geometry in regulating the coupling between discharge activation and mass transport remains insufficiently explored. Inspired by the generalized Murray's law for geometric transport optimization and hierarchical scale matching, this work considers the internal cavity, shell diffusion pathway, and mesoporous channels as coupled multiscale transport units, and constructs hierarchical hollow Cu/TiO₂ catalysts with tunable cavity-shell ratios. Thin, Thick, and Solid samples were employed as comparative catalysts to systematically investigate the influence of cavity-shell matching on dielectric barrier discharge (DBD)-assisted reverse water-gas shift (RWGS) reaction performance. The results show that the Thin sample, which approaches the Murray-like cavity-shell matching trend, exhibits the best CO₂ conversion performance, achieving a CO₂ conversion of 37.11%, higher than those of Thick and Solid samples, 31.77% and 22.06%, respectively, while maintaining stability and energy utilization. Structural characterization, optical emission spectroscopy (OES), and COMSOL simulations reveal that the Thin configuration shortens the cross-shell transport pathway, enhances the local electric field and electron density, and promotes the near-surface enrichment of vibrationally excited CO₂ species. Complementary H₂ temperature-programmed desorption (H₂-TPD) and hydrogen evolution reaction (HER)-assisted measurements further reveal a broader distribution of accessible hydrogen-related adsorption states and more favorable interfacial charge transfer over the Thin sample. This study demonstrates that Murray-inspired hollow-shell structures can establish effective coupling among geometric transport matching, local discharge activation, and interfacial reaction utilization.