The influence of CsHSO4 inorganic solid acid was evaluated as a possible proton conductor in the catalyst layer of ABPBI (poly(2,5-benzimidazole))-based high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Gas diffusion electrodes (GDEs) were prepared with fixed polytetrafluoroethylene (PTFE) and polyvinylidene diflouride (PVDF) binder content, while the CsHSO4 loading was varied. Porosimetry data showed that the addition of 10 % CsHSO4 to the PVDF GDE increased the porosity across all the pore regions, whereas the addition of 10 % CsHSO4 to the PTFE GDE decreased the GDEs porosity. The CsHSO4 MEAs showed good proton transfer dynamics and low resistance for fuel cell operation. An optimum loading of 10 % CsHSO4 in conjunction with either of the binders was observed, with CsHSO4-PVDF GDE achieving peak power of 498.2 mW cm(-2) at a cell voltage of +352 mV. Higher CsHSO4 loadings increased the charge transfer resistance and lowered the cell performance of these GDEs.