Synthesis of a Pt/C Electrocatalyst from a User-Friendly Pt Precursor (Ammonium Hexachloroplatinate) through Microwave-Assisted Polyol Synthesis

Ammonium hexachloroplatinate (NH4)2PtCl6, owing to its low solubility in NH4Cl-containing aqueous solutions, is an intermediate compound during the hydrometallurgical extraction of platinum. As a rare example of a water-soluble and air-stable platinum(IV) salt that is not hygroscopic, (NH4)2PtCl6 may be a convenient and economic platinum precursor for large-scale catalyst production. This report investigates the feasibility of (NH4)2PtCl6 as a Pt precursor for synthesis of the electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs), i.e., where there is Pt supported on high surface area carbon (Pt/C). The Pt/C electrocatalysts with ∼20 wt % Pt loading are synthesized through a microwave-assisted polyol synthesis approach. The reaction parameters, namely, the reaction time and the reaction temperature, are optimized. In terms of the electrochemical surface area, the Pt/C electrocatalyst synthesized at a reaction temperature of 140 °C and a reaction time of 150 s using a Pt concentration of 5 mM exhibited the optimal performance. The process may be used to synthesize Pt/C electrocatalysts having an electrochemical performance equivalent to the Pt/C catalyst available commercially or that synthesized using the common precursors such as H2PtCl6.