Abstract
Proton exchange membrane (PEM) water electrolysis powered by renewable energies is seen as one of the most powerful techniques for the high production of ultra-pure hydrogen. However, PEM requires of noble metals as catalysts while operating under harsh acidic conditions, creating a detrimental environment which conducts to fast corrosion of the catalyst. Reducing and extending the lifetime of noble metals under acidic conditions will benefit the hydrogen economy. Currently, one of the major limitations relies on the high corrosion that anode electrocatalysts suffer, where the oxygen evolution reaction (OER) takes place. The best performing electrocatalysts are based on ruthenium (Ru) and iridium (Ir) either in the pure oxide form or as engineered composites, being Ru the most active but less stable even at moderate cell potentials. Here, we investigate the quaternary Sn-Sb-Mo-W mixed oxide (MO) as an effective scaffold to protect RuO2 for corrosion. The acid-stable MO was produced via plasma spraying forming an interconnected network of nanostructured WO3, Sb2O3, SnO2, and MoO3. Low quantities of Ru (2.64% w/w Ru) were stabilized into the matrix (Ru-MO) and finally supported on FTO. The Ru deactivation was described by a second-order reaction with a deactivation rate constant of k = 0.067 cm2 (mA·min)-1. Titanium fiber felt was later used as support (Ru-MO@Ti) where a mass activity of 4440 A g-1 Ru@1.8V(RHE) was obtained, and solely a reduction of 20% was seen in the OER activity after 2000 CVs (1.2 – 1.8 V vs RHE), in contrast to unprotected RuO2 (RuO2@Ti) which showed an activity loss of nearly 90%. In addition, chronopotentiometry studies on Ru-MO@Ti (2.5 A cm-2 @ 1.7V) confirmed the high satiability of the Ru experienced only a minor increase in potential of 10 mV, while RuO2@Ti exhibited a significant degradation of 500 mV after 10 h. The superior stability of Ru-MO@Ti was possible due to impeded formation of higher valence ruthenium (Ru+8), a typical dissolution path for Ru-based electrocatalysts. Our work shows that multi-metal oxides have the potential to host and extend the lifetime of active metals and Ti substrates when used for water electrolysis in acidic media. Figure 1
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