Photo-assisted synthesis of protonated oxides for fuel cells

The absence of intrinsic protons in proton-conducting oxides (PCO) is a significant challenge that limits the proton conductivity of proton-conducting perovskites, such as Y-doped BaMO₃ (M = Zr, Ce), in proton ceramic fuel cells exhibit low conductivity (10^-3 to 10^-2 S cm^-1 at 600 °C). Herein, we introduce a photo-assisted synthesis method for incorporating protons into Al-doped ceria (Al_xCe_1-xO_2-δ, x = 0.2; M-ACO), leveraging the open cubic fluorite structure and photo-activated radical reactions. Specifically, photon-generated hydroxyl reactive <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mfenced> <mml:mrow> <mml:msup><mml:mrow><mml:mi>OH</mml:mi></mml:mrow> <mml:mrow><mml:mo>∙</mml:mo></mml:mrow> </mml:msup> </mml:mrow> </mml:mfenced> </mml:math> and superoxide ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup><mml:mrow><mml:mi>O</mml:mi></mml:mrow> <mml:mrow><mml:mn>2</mml:mn></mml:mrow> <mml:mrow><mml:mo>∙</mml:mo> <mml:mo>-</mml:mo></mml:mrow> </mml:msubsup> </mml:math> ) Radicals are generated and interact with the ACO crystal lattice, facilitating proton incorporation and resulting in the synthesis of native-proton-type PCO. This process results in a protonated (H-ACO) with a high proton conductivity of 0.14 S cm^-1 and exceptional power density of 922 mW cm^-2 at 500 °C. This versatile synthesis methodology offers broader development of advanced PCO for energy-related applications.