Construction of diffusion and binding synergy in carbon-supported catalysts with varied Pd⁰/PdO Ratios for direct synthesis of hydrogen peroxide

In heterogeneous reactions, catalyst support plays an important role in tuning catalytic activity of metallic structures and regulating fluid transport during reaction, while it needs to be engineered to balance reaction and diffusion for optimized outcome. In this work, a combined delignification and activation strategy was used to prepare a series of carbon supports with varied porous structures and surface properties. Pd was then loaded on the carbon supports for direct synthesis of H₂O₂ (DSHP) reaction. Results indicated that highly developed meso-macropore structures significantly promoted the dispersion of Pd and exposed more active sites for H₂ dissociation. However, the enrichment of pore structure brought excessive surface oxygen groups, leading to the transition of Pd from Pd⁰ to PdO and thus inhibiting the hydrogenation activity. The optimized catalyst, with desirable porous structure and appropriate Pd⁰/PdO ratio, exhibited an extraordinarily high H₂O₂ productivity of 37346.42 mmol g_Pd⁻¹h⁻¹ under atmospheric conditions. This work provided a case study on the regulation of reactivity and diffusion through catalyst support engineering, demonstrating the essential role of matched reaction–diffusion in heterogeneous DSHP reactions.