Enhanced Formic Acid Dehydrogenation over Basic Site-Rich Pd/Al2O3 Hollow Sphere Catalyst

Formic acid (FA) is regarded as a safe and practical hydrogen carrier owing to its favorable storage and handling characteristics. However, achieving efficient and selective FA dehydrogenation under mild conditions remains a significant challenge. In this study, the decomposition pathway of FA was found to be highly dependent on the acid–base characteristics of the catalyst support, with basic surfaces preferentially favoring the dehydrogenation route. Therefore, a morphology-regulated strategy was developed to modulate the distribution of basic sites on alumina, revealing a direct structure–function relationship that governs the catalytic behavior. Al2O3 hollow spheres (HS), featuring abundant surface basicity, were synthesized via a hydrothermal method and used as supports for Pd catalysts alongside Al2O3 nanobelts (NB) and nanoparticles (NP). Mechanistic studies integrating catalytic evaluation, in situ DRIFTS, and CO2-TPD analyses demonstrated that the Pd/Al2O3–HS catalyst, owing to its support enriched in basic sites, simultaneously facilitates formate formation and promotes the generation of the Pd–HCOO* intermediate, thereby enhancing H2 production. This synergy results in superior catalytic performance (TOF = 4606 h–1) with no detectable CO formation. The increased basicity of the support markedly improved the hydrogen evolution during formic acid decomposition, highlighting a strong correlation between support basicity and catalytic efficiency.