Hydrogen-Tolerant La₀.₆Ca₀.₄Co₀.₂Fe₀.₈O₃₋d Oxygen Transport Membranes from Ultrasonic Spray Synthesis for Plasma-Assisted CO₂ Conversion

La₀.₆Ca₀.₄Co₁₋ₓFeₓO₃₋d in its various compositions has proven to be an excellent CO₂-resistant oxygen transport membrane that can be used in plasma-assisted CO₂ conversion. With the goal of incorporating green hydrogen into the CO₂ conversion process, this work takes a step further by investigating the compatibility of La₀.₆Ca₀.₄Co₁₋ₓFeₓO₃₋d membranes with hydrogen fed into the plasma. This will enable plasma-assisted conversion of the carbon monoxide produced in the CO₂ reduction process into green fuels, like methanol. This requires the La₀.₆Ca₀.₄Co₁₋ₓFeₓO₃₋d membranes to be tolerant towards reducing conditions of hydrogen. The hydrogen tolerance of La₀.₆Ca₀.₄Co₁₋ₓFeₓO₃₋d (x = 0.8) was studied in detail. A faster and resource-efficient route based on ultrasonic spray synthesis was developed to synthesise the La₀.₆Ca₀.₄Co₀.₂Fe₀.₈O₃₋d membranes. The La₀.₆Ca₀.₄Co₀.₂Fe₀.₈O₃₋d membrane developed using ultrasonic spray synthesis showed similar performance in terms of its oxygen permeation when compared with the ones synthesised with conventional techniques, such as co-precipitation, sol–gel, etc., despite using 30% less cobalt.