Exchange current density of the hydrogen oxidation reaction on Pt/C in polymer solid base electrolyte

• An H2 pump was used to measure the HOR activity on Pt in polymer solid electrolytes.
• This is the first report of HOR activity in a polymer solid base electrolyte.
• The HOR activity in the polymer solid base electrolyte is similar to that in liquid base electrolytes.
• The HOR activity in the polymer solid base electrolyte is ~ 100 times lower than in a polymer solid acid electrolyte.

The exchange current density of the hydrogen oxidation reaction (HOR) on platinum supported on carbon (Pt/C) has been widely studied for liquid base electrolyte (LBE), but has yet to be reported for a polymer solid base electrolyte (SBE). The goal of this study is to determine the exchange current density for the HOR on Pt/C in an SBE using a hydrogen pump and to compare it with those in LBE and a polymer solid acid electrolyte (SAE). We find that the HOR activity in the SBE is almost the same as in LBE, and is nearly two orders of magnitude lower than in SAE. The similar HOR activities on Pt/C in SBE and LBE suggest that previously reported exchange current densities measured in LBE accurately reflect Pt/C's activity for the HOR in SBE fuel cells even though the modes of ion conduction in liquid and solid polymer electrolytes are inherently different.