Abstract
This paper describes an experimental evaluation and comparison of Pt/C and Pt-Ru/C electrocatalysts for high-temperature (100–160 °C) electrochemical hydrogen separators, for the purpose of mitigating CO poisoning. The performances of both Pt/C and Pt-Ru/C (Pt:Ru atomic ratio 1:1) were investigated and compared under pure hydrogen and a H2/CO gas mixture at various temperatures. The electrochemically active surface area (ECSA), determined from cyclic voltammetry, was used as the basis for a method to evaluate the performances of the two catalysts. Both CO stripping and the underpotential deposition of hydrogen were used to evaluate the electrochemical surface area. When the H2/CO gas mixture was used, there was a complex overlap of mechanisms, and therefore CO peak could not be used to evaluate the ECSA. Hence, the hydrogen peaks that resulted after the CO was removed from the Pt surface were used to evaluate the active surface area instead of the CO peaks. Results revealed that Pt-Ru/C was more tolerant to CO, since the overlapping reaction mechanism between H2 and CO was suppressed when Ru was introduced to the catalyst. SEM images of the catalysts before and after heat treatment indicated that particle agglomeration occurs upon exposure to high temperatures (>100 °C)
Highlights
Accepted: 25 August 2021Electrochemical hydrogen separators (EHSs) show great potential for future hydrogenbased energy scenarios
A variety of reaction possibilities was considered, which basically include the assumption that CO is either reduced [61] or oxidized [62]
No side reactions were evident in the absence of H2
Summary
Electrochemical hydrogen separators (EHSs) show great potential for future hydrogenbased energy scenarios. The main advantage that EHSs offer is the simultaneous compression and purification of hydrogen for fuel cell (FC) application and storage purposes [1,2,3]. Perfluorinated sulfonic acid (PFSA) membranes (mainly Nafion-based), typically operated at 60–80 ◦ C, are generally used as proton exchange membranes (PEMs) due to their high proton conductivity, mechanical integrity, and chemical stability [4]. Pt-based materials are still the most favored electrocatalysts, the focus of much current research is on alternative catalysts. Pt-based electrocatalysts offer effectiveness, high chemical stability, high current density, and good activities for hydrogen oxidation/evolution reactions in EHSs and oxygen reduction reactions in FCs [5,6]. Pt does have some disadvantages: resources are limited, it is costly, and Pt is prone to poisoning/deactivation [6,7,8]
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