The low overpotential regime of acidic water oxidation part II: trends in metal and oxygen stability numbers

Abstract

The operating conditions of low pH and high potential at the anodes of polymer electrolyte membrane electrolysers, restrict the choice of catalysts for the oxygen evolution reaction (OER) to oxides...

Ruthenium oxychloride supported by manganese oxide for stable oxygen evolution in acidic media

“…It is noteworthy that the elevated oxidation potential is crucial for enhancing the stability. The dissolution of the RuO 2 lattice, which is triggered by the loss of lattice/surface oxygen accompanied by the sharing of OER intermediates, 7,59 depends on the applied potential, and it becomes more severe when the potential is much higher than the theoretical redox potential (1.39 V RHE , pH 0) 6 . The dispersion of Ru into the MnO x support results in a high oxidation potential of the catalyst and therefore long-term stability even at high current density.…”

“…The adsorbate evolution mechanism (AEM) is mainly considered here because a recent report suggests that the lattice oxygen evolution makes a negligible contribution to the overall OER activity of RuO x in acidic electrolyte. 59 The energy of O 2 in an ideal catalysis process is estimated to be Δ G O 2 = 4 × 1.23 = 4.92 eV since it is a four-electron-transfer process. 62 Comparing the Gibbs free energy on different surfaces, the reaction process of the Ru2 site on the Mn 2 O 3 Ru (110) surface is closer to the ideal catalysis process than that of pure RuO 2 and the Ru1 site on the Mn 2 O 3 Ru (110) surface, since the theoretical overpotentials for the Ru2 site on Mn 2 O 3 Ru (110), RuO 2 , Ru1 site on Mn 2 O 3 Ru (110), and Mn site on Mn 2 O 3 Ru (110) surfaces are 0.75, 0.99, 1.11, and 1.32 V, respectively.…”

Stability Design Principles of Manganese-Based Oxides in Acid

“…For instance, while bulk MnO 2 is relatively stable at the open circuit and even at OER/ORR potentials (Figure a), the MnO 2 surface can be reduced to Mn 2+ under ORR conditions, , which can explain the lack of existing acid-stable Mn-based oxide ORR catalysts, as Mn 2+ cations in oxides are unstable in acid. In contrast, stabilizing Mn-based oxides at OER potentials − ,, is easier, as the surface of these oxides becomes Mn 4+ under OER conditions. , However, it is crucial to note that, beyond metal redox, a variety of surface transformations (e.g., ion leaching and surface amorphization) have been observed for oxide catalysts under electrochemical conditions. − Future studies are required to establish descriptors for possible electrochemically induced evolution of oxide surfaces, for example, by leveraging operando spectroscopic or microscopic characterizations and first-principles simulations of catalyst–electrolyte interfaces. In addition, in this work, we focused on identifying physical principles governing the thermodynamic chemical and electrochemical stability of Mn-based oxides in acid, as well as their chemical dissolution kinetics, as a starting point for the stability design principles of these oxides in acid.…”

“…6,27 However, it is crucial to note that, beyond metal redox, a variety of surface transformations (e.g., ion leaching and surface amorphization) have been observed for oxide catalysts under electrochemical conditions. 74−77 Future studies are required to establish descriptors for possible electrochemically induced evolution of oxide surfaces, for example, by leveraging operando spectroscopic 78 or microscopic characterizations 79 and first-principles simulations 80 of catalyst−electrolyte interfaces. In addition, in this work, we focused on identifying physical principles governing the thermodynamic chemical and electrochemical stability of Mn-based oxides in acid, as well as their chemical dissolution kinetics, as a starting point for the stability design principles of these oxides in acid.…”

In Situ Synchrotron-Based Studies of IrO2(110)–TiO2(110) under Harsh Acidic Water Splitting Conditions: Anodic Stability and Radiation Damages

“…39 The explanation is based on the lattice oxygen evolution reaction (LOER) 2O We have to emphasize that this general thermodynamic argument of Binninger et al cannot be applied for explaining the missing dissolution behavior of the IrO 2 (110) film. However, from oxygen isotope labeling experiments, 40,41 it was concluded that only the surface oxygen of IrO 2 participates in the OER reaction. Therefore, the missing LOER-induced instability of IrO 2 (110) is explained by kinetic reasons.…”