Pd–Ag alloy membranes (0.4 μm) have been prepared on porous TiO 2 /Al 2 O 3 support via a photocatalytic co-deposition technique. Using this technique the membrane composition can be precisely controlled and the alloying of Pd–Ag carried out more easily. X-ray diffraction and scanning electronic microscopy analysis of the Pd–Ag composite membranes indicated that the metal existed in the form of alloy and membrane surface appeared homogeneous. A gas permeation experiment was conducted under temperature of 693 K and pressure of 0.01–0.06 MPa. Hydrogen permeance and selectivity of hydrogen/nitrogen (H 2 /N 2 ) were 1×10 −5 mol m −2 s −1 Pa −1 and 7.1–7.4, respectively.