H-2 permeability of the mixed protonic and electronic conducting membranes can be enhanced by the adjustment of the operating conditions. BaCe0.8Y0.2O3-delta (BCY)-Ce-0.8-Y0.20O2-delta (YDC)/BCY Ni hollow fiber membranes were prepared, and their H-2 permeation fluxes under a gas atmosphere containing water vapor and CO, were systematically investigated. The influences of H-2 partial pressure in feed stream, steam, or CO2 concentration in sweep gas, sweep gas flow rate, and operating temperature on H-2 permeation fluxes were studied. When the sweep side was humidified, the H-2 permeation flux of the membrane was increased and reached 1.21 mL cm(-2) min(-1) at 900 degrees C. When using 20% CO2-N-2 as the sweep gas, H-2 permeation flux of the membrane was further increased because of the presence of the reverse water-gas shift (RWGS) reaction, achieving 3.03 mL cm(-2) min(-1) at 900 degrees C, one of the highest H-2 fluxes ever reported for mixed protonic and electronic conducting membranes. Without adding extra catalyst, the conversion of CO2 reached 42.5% when using 7% CO2-N-2 as the sweep gas at 900 degrees C, indicating that the membrane material itself has a certain catalytic activity for RWGS. In addition to the excellent H-2 permeability, the membrane also showed good stability in a H-2 CO2-containing atmosphere, highlighting its promising application as the membrane reactor for H-2 separation and CO2 transformation.