Light-Activated Dual-Site Pathway Enables Efficient Hydrogen Release From Dodecahydro-N-ethylcarbazole.

Abstract

Dodecahydro-N-ethylcarbazole (12H-NEC) is a promising liquid organic hydrogen carrier (LOHC), yet its practical application is still constrained by slow dehydrogenation kinetics and extreme reliance on external heating even over most effective Pd-based catalysts. Here we identify that the hydrogen removal step with a high barrier is the precise kinetic bottleneck of 12H-NEC dehydrogenation, which remains underexplored. To effectively overcome this limitation, we report a light-activated dual-site hydrogen removal pathway using Pd nanoparticles supported on defective N-doped TiO2. Under irradiation, charge transfer from the support to Pd weakens Pd-H interactions, while accumulated holes on the support promote hydrogen spillover to Ti defect sites, generating weakened Ti-H species alongside Pd-H. This thereby initiates a new hydrogen formation dual-site pathway by combining Pd-H and Ti-H with an overall dehydrogenation barrier of 0.46 eV only, 0.74 eV lower than the conventional thermal Pd-localized pathway, resulting in a 42-fold higher H2 release rate relative to dark conditions at 140°C. Even under concentrated natural sunlight without external heating, near-complete dehydrogenation with a capacity of 5.65 wt.% H2 within 1 h is achieved from 12H-NEC. This work charts a promising course for practical hydrogen storage applications of LOHCs without secondary energy input.