Pt-alloy Catalyst Used as Recombination Catalyst in a Thin Polymer Electrolyte Membrane Electrolyser

Various Pt-based materials were investigated as catalysts for recombining hydrogen and oxygen back into water. The recombination performance correlated well with the surface Pt metallic state. Alloying cobalt to platinum was observed to produce an electron transfer favouring the occurrence of a large fraction of the Pt metallic state on the catalyst surface. Unsupported PtCo showed both excellent recombination performance and dynamic behaviour. In a packed bed catalytic reactor, when hydrogen was fed at 4% vol. in the oxygen stream, 99.5% of the total H2 content was immediately converted to water in the presence of PtCo thus avoiding safety issues. The PtCo catalyst was thus integrated in the anode of the membrane-electrode assembly of a polymer electrolyte membrane electrolysis cell operating up to 4 A·cm-2 current density. This catalyst showed good capability to reduce the concentration of hydrogen in the oxygen stream under differential pressure operation, in the presence of a thin (50 and 90 ?m) Aquivion® membranes.