Phase Engineering\nof Zirconia Support Promotes the\nCatalytic Dehydrogenation of Formic Acid by Pd Active Sites

The development of Pd-based catalysts with outstanding\nactivity\nand stability can further promote the hydrogen storage application\nof formic acid (FA). Regulating the support structure is an effective\nstrategy for enhancing active sites in heterogeneous catalytic systems.\nThis study prepared three types of nanosized ZrO<sub>2</sub> through\nphase engineering to support Pd metal and investigated the implications\nof support structure on the microenvironment of active sites, thus\nrevealing the structure–activity relationship of the catalysts.\nThe hollow nanoframes like Pd/ZrO<sub>2</sub>-F with a moderate t-ZrO<sub>2</sub> content exhibit remarkable stability and catalytic performance\nwith a TOF of 1348 h<sup>–1</sup> at an ambient temperature.\nDensity functional theory (DFT) calculations verify that the crystal\nphase of ZrO<sub>2</sub> can dramatically affect the metal–support\ninteraction and change the Pd electronic state. Moreover, the dehydrogenation\nenergy profiles reveal the synergy effect between ZrO<sub>2</sub> phases\non Pd active sites in the reaction. Pd/m-ZrO<sub>2</sub> is more conducive\nto the dissociation of FA, and Pd/t-ZrO<sub>2</sub> has energy advantages\nin hydrogen recombination. This work provides a new perspective for\nunderstanding the synergistic effect of the zirconia crystal phase\non formic acid dehydrogenation by Pd active sites.