A novel strategy to enhance hydrothermal stability of Pd-doped organosilica membrane for hydrogen separation

Pd-doped organosilica (POS) membranes are calcined in N₂ and steam atmospheres for hydrogen separation. Chemical compositions and microstructures of the membranes are characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR) and N₂ absorption-desorption measurement. Gas separation performances and hydrothermal stabilities of the membranes are also evaluated and compared. The membrane calcined in steam atmosphere (i.e. POS-S membrane) shows a high H₂ permeance (2.5 × 10⁻⁷ mol·m⁻²·s⁻¹·Pa⁻¹) and H₂/CO₂ permselectivity (9.2, doubles the Knudsen diffusion factor 4.69). Notably, compared with the POS membrane calcined in N₂, the POS-S membrane displays more excellent hydrothermal stability throughout a 190-h test, which is superior to most silica-derived membranes reported. The significantly enhanced hydrothermal stability is mainly attributed to the low content of unstable moieties in the POS network after steam calcination. Steam conditions make unstable intermediate Pd oxide transfer into stable PdO and reduce content of inorganic moieties during the calcination, leading to high hydrothermal stability of the membrane. Therefore, calcination in steam atmosphere may offer an effective strategy to develop desirable POS membranes with high separation performances and excellent hydrothermal stabilities for practical hydrogen separation.