Self-assembled synthesis of Pd/SPEn from polyelectrolyte membranes for efficient direct synthesis of H2O2 via inhibiting the dissociation of O − O bond

The partial enlarged view of the left region is shown on the right. On conventional Pd/SiO2, the length of the O-O bond is usually 0.135 nm because Pd transfers electrons to O2–*(*, adsorbed state). Longer bonds are easy to cause the dissociation of O-O bonds, which tends to form H2O, resulting in low H2O2 selectivity (70.6%) and yield (2856 mmol∙gPd-1∙h−1). In the Pd/SPE prepared herein, the length of the O-O bond was reduced to 0.128 nm because Pd transfers electrons to N in PDDA, which significantly inhibited the dissociation of the O-O bond and tended more toward the formation of H2O2, leading to high H2O2 selectivity (90.1%) and yield (5764 mmol∙gPd-1∙h−1). [Display omitted] •A novel catalyst (Pd/SPEn) by assembling polyelectrolyte membranes on SiO2 surface.•Polyelectrolyte membrane can anchor Pd nanoparticles and make them highly dispersed.•Polyelectrolyte membrane can promote the electrons transfer from Pd to N.•The best catalyst (Pd/SPE5) still has strong stability even after 5 cycles.•The O-O bond distance of O2* on Pd/SPE (1.282 Å) is shorter than Pd/SiO2 (1.350 Å). Although a high-activity yield of hydrogen peroxide (H2O2) can be achieved by direct synthesis from hydrogen and oxygen, developing an extreme catalyst with high activity and stability is still very challenging, which limits its industrial application. Here, we reported a catalyst Pd/SPE with polyelectrolyte membranes SPE as an electronic acceptor to anchor Pd, which achieves H2O2 selectivity of 90.1% and productivity of 5764.4 mmol∙gPd-1∙h−1. The results of TEM, XRD and ICP-MS, XPS, CO-DRIFT, O2-TPD, synchrotron radiation and density functional theory (DFT) simulations reveal that the electrons of Pd are transferred into polyelectrolyte membranes and Pd clusters are strongly chemisorbed on SPE, which is beneficial for O2 adsorption and inhibits the dissociation of O-O bond, leading to significantly enhanced H2O2 productivity and selectivity.