Mussel-inspired dopamine-modified silica microspheres for anchoring PdNi bimetallic nanoclusters: Unlocking superior catalysts for efficient H2O2 synthesis

The direct synthesis of hydrogen peroxide (DSHP) through the reaction of hydrogen and oxygen under atmospheric pressure offers a highly atom-economic and environmentally friendly approach. However, this process is hindered by low productivity and selectivity of H 2 O 2 . Inspired by the adhesive properties of mussels, we successfully developed a bimetallic nanocluster catalyst, Pd x Ni y /SiO 2 @PDA, leveraging strong metal-support interactions (SMSI) for enhanced catalytic performance. Among these, the catalyst Pd 0.7 Ni 0.3 /SiO 2 @PDA demonstrated exceptional catalytic activity, achieving H 2 O 2 productivity and selectivity of 7210.60 mmol/g Pd ·h -1 and 95.30 %, respectively—representing improvements of 319.51 % and 33.50 % over the unmodified Pd/SiO 2 catalyst (1718.84 mmol/g Pd ·h -1 and 61.80 %). The anchoring mechanism of phenolic hydroxyl and amino groups on the polydopamine (PDA) coating was systematically investigated using control groups modified with tea polyphenols (TP) and 3-aminopropyltriethoxysilane (APTES), rich in phenolic hydroxyl and amino groups, respectively. Characterization revealed that amino groups on the PDA layer served as the primary anchoring sites, and the phenolic hydroxyl and quinone groups play a role in optimizing the electronic structure of Pd in an electron-deficient state. Synchrotron-based X-ray absorption fine structure (XAFS) analysis and density functional theory (DFT) calculations further revealed that the incorporation of Ni, a metal with a smaller atomic radius and lower electronegativity, reduced the Pd-Pd interatomic distance and shift the d -band center downwards from -1.72 eV to -1.94 eV. This modification inhibited the dissociative adsorption of O 2 * at Pd sites, thereby significantly enhancing H 2 O 2 productivity and selectivity.