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Catalyst; Degradation; Fuel cells; Oxygen evolution; Stability
Abstract:
Commercial proton exchange membrane (PEM) fuel cells, various types of water electrolyzers and recently proposed unified, regenerative fuel cells are usually operated at elevated temperatures. Higher-operation temperatures bring several advantages: (a) increase of the rate of slow oxygen reactions, (b) improved mass transport, and (c) minimization of the electrolyte (ionic conductor) resistance. However, at the same time, it is expected that degradation processes will be accelerated at such temperatures. In the current work, electrochemistry and in situ mass spectrometry are utilized to investigate how increased temperature affects the rate of (electro)chemical dissolution of platinum. The steady state dissolution rate during potentiostatic polarization decreases to a value below the detection limit after several minutes at all temperatures-dissolution thus remains a transient process controlled by oxide formation kinetics as reported previously for room temperature. Deconvolution of anodic and cathodic dissolution branches in potentiodynamic experiments reveals that the increase in temperature results in higher amounts of platinum being dissolved during oxide formation, while dissolution during oxide reduction decays with increasing temperature. In contrast to most literature reports, the total amount of dissolved platinum during 1 potential cycle is found to decrease with increasing temperature.
