3D-printed Pd/AC catalytic impellers for overcoming mass transfer limitations in hydrogen production from formic acid

Integral 3D-printed Pd/AC catalytic impellers were developed for intensified hydrogen production via formic acid (FA) dehydrogenation. Three-bladed structures with different infill densities (35, 50 and 100%) were fabricated by direct ink writing of whey-derived precursors. Pd (5 wt%) was incorporated by wet impregnation, producing catalysts with similar properties (Pd particle size ∼2 nm, dispersion ∼45%, Pd 2+ /Pd 0 ≈ 7). The CAT#35 impeller (35% infill) showed the best performance, with TOF 0 three times higher than the dense CAT#100. This improvement was attributed to the open mesh architecture, which mitigated external mass transfer limitations, while maintaining stable activity over 15 cycles and 140 h of operation. A kinetic model based on a Langmuir-Hinshelwood-Hougen-Watson equation with a first-order dependence on FA concentration and hydrogen inhibition (E a = 34.8 kJ mol −1 ) was proposed. Catalyst deactivation followed a first-order decay model with residual activity, depending on the temperature and initial FA concentration.