Dual-Site Relay Catalysis over La2O3-Engineered Pd Nanostructure for Additive-Free and CO-Free Hydrogen Release from Formic Acid

Abstract

Formic acid (FA), when derived from captured CO₂ and renewable H₂, is a promising liquid hydrogen carrier, but its sustainable use requires catalysts that enable fast, CO-free, and additive-free hydrogen release under mild conditions. Herein, we report a nanoscale La₂O₃-modified porous N-doped carbon-anchored ultrafine Pd nanoparticle catalyst La₂O₃-engineered porous carbon-nitrogen-supported Pd catalyst, Pd−La₃CN-750, for efficient FA dehydrogenation. The introduced nanosized La₂O₃ species are uniformly dispersed on the porous carbon-nitrogen support, which precisely regulates the interfacial microstructure of Pd nanoparticles. La₂O₃ incorporation reconstructs the Pd/support interface by creating defect-rich anchoring sites, introducing medium-strength basic sites, and inducing interfacial electron transfer to enrich electron-deficient Pd^δ+ species. As a result, Pd−La₃CN-750 achieves a complete aqueous FA dehydrogenation within 8 min at 313 K, with a TOF of 1431 h⁻¹, a low apparent activation energy of 42.36 kJ mol⁻¹, no detectable CO formation, and stable reusability over seven cycles. In situ DRIFTS and density functional theory calculations reveal a nanoscale interfacial dual-site relay mechanism, in which La−O basic sites activate the O−H bond of FA to generate formate intermediates, while adjacent Pd⁰−Pd^δ+ ensembles promote C−H cleavage, H−H coupling, and H₂ desorption. This interfacial synergy lowers the dehydrogenation barrier while suppressing the CO-forming dehydration route. From a sustainability perspective, the catalyst offers low-temperature atmospheric-pressure operation, eliminates sacrificial additives, maximizes the utilization efficiency of ultrafine Pd active nanoparticles, and produces a CO-free hydrogen stream, while future optimization should address synthesis-stage impacts from hard templating, high-temperature carbonization, alkaline etching, solvent use, and H₂ reduction. This work provides a sustainability-oriented interfacial design strategy for efficient hydrogen release from carbon-recyclable liquid carriers.