Application of a composite electrolyte in a solid-acid fuel cell system: A micro-arc oxidation alumina support filled with CsH2PO4

•Micro-arc oxidation alumina (MOA) support filled with CsH2PO4 proton conductor.•Composite MOA/CsH2PO4 membrane applied for solid-acid fuel cell (SAFC).•An interlaced network distribution of CsH2PO4 in MOA support.•MOA/CsH2PO4 SAFC sustained a high and stable power output.•MOA/CsH2PO4 SAFC showed a power loss of 15% after a stability performance test.

A micro-arc oxidation alumina (MOA) support filled with a CsH2PO4 proton conductor was investigated as an inorganic composite electrolyte for a H2/O2 solid-acid fuel cell (SAFC). The MOA support was polycrystalline and contained α- and γ-Al2O3 phases; while, the proton conductor CsH2PO4 formed an interlaced network within the MOA support. The single-module SAFC using the fabricated MOA/CsH2PO4 membrane delivered a peak power of ∼38.5 m W cm−2 and a proton conductivity of ∼2.1 m S cm−1 at a low temperature (25 °C). Compared to a SAFC using an anodic alumina membrane composite electrolyte (AAM/CsH2PO4 SAFC), which displayed rapid degradation, the SAFC using the MOA/CsH2PO4 composite electrolyte showed improved stability with cycling. This was attributed to the crystalline α-Al2O3 phase that was part of the MOA support that had increased the chemical resistance.