Influence of Pd/AC Catalytic Properties on the Continuous Production of Hydrogen from Formic Acid

Abstract

Formic acid (FA) is a promising liquid organic hydrogen carrier for safe and efficient hydrogen handling. FA dehydrogenation occurs under near-ambient conditions using palladium/activated carbon (Pd/AC) catalysts, but aspects like high Pd loading and gradual catalyst deactivation remain key challenges. This study investigates how the physicochemical properties of Pd nanoparticles and support characteristics influence the continuous process performance including FA conversion, evolved gas flow rate, total hydrogen production, and catalyst durability. Pd catalysts were prepared via wet impregnation using various precursors, powdered supports, and Pd loadings and evaluated in a fixed-bed reactor. The findings reveal that Pd/AC catalysts prepared with PdCl₂ precursor and nanopowdered AC are the most efficient. Strong electrostatic interactions between negatively charged PdCl₄2⁻ species and the positively charged AC surface during impregnation enhance nanoparticle support interactions, resulting in small (∼2 nm), highly dispersed Pd nanoparticles with a high Pd2⁺/Pd⁰ atomic surface ratio. Metal dispersion is the dominant factor influencing hydrogen production, surpassing the effects of both particle size and electronic state. Higher Pd loadings also increased catalyst durability, reducing regeneration frequency. This study provides valuable insights into the rational design of Pd/AC catalysts, paving the way for efficient FA utilization as a hydrogen carrier.