Oxygen Reduction Reaction

Abstract

In this chapter, the oxygen reduction reaction (ORR), which is one of the most important reactions in energy conversion systems such as fuel cells, including its reaction kinetics, is presented. Recent developments in electrocatalysts for ORR in fuel cells, including low and non-Pt electrocatalysts, metal oxides, transition metal macrocycles and chalgogenides, are discussed. Understanding of the interdependence of size, shape and activity of the electrocatalysts is evaluated. The recent development of ORR electrocatalysts with novel nanostructures is also reported. The mechanism catalysed by these electrocatalysts is presented. Finally, the perspectives of future trends for ORR are discussed.

Plausible Physical Mechanisms for Unusual Volatile/Non- Volatile Resistive Switching in HfO2-Based Stacks

“…Moreover, the Pd layer follows the topographic landscape of the outermost Co surface and no inter-diffusion can be clearly identified. On the contrary, the smooth transition from the HfO 2 to the Co layer seems to suggest that oxygen is present (or even HfO 2 ) within the Co layer, which could be explained in terms of its reactivity and scavenging ability [11]. As can be observed in Figure 2, specifically regarding the TiO x layer, a columnar arrangement of alternating brighter and darker areas is noticeable, which indicates inhomogeneous and localized oxidation.…”

Local probe investigation of electrocatalytic activity

“…The reactions of both pathways in acidic and alkaline media are presented below as (2)–(7) . 109 The detailed mechanism of the ORR is rather convoluted and it depends on the electrocatalyst; however some proposed mechanisms are summarized by Nie et al 110 …”

Biomass Related Highly Porous Metal Free Carbon for Gas Storage and Electrocatalytic Applications

“…The four-electron reduction pathway transforms O2 directly to H2O. The other route is a two-electron pathway through peroxide formation [67]. In polymer electrolyte membrane fuel cells (PEMFCs) the preferred ORR pathway is a four-electron transfer.…”

“…In polymer electrolyte membrane fuel cells (PEMFCs) the preferred ORR pathway is a four-electron transfer. Depending on the pH of the reaction media the 4e − reduction route has different thermodynamic potentials ranging from 0.401 V in alkaline media (Equation ( 4)) to 1.230 V in acidic media (Equation ( 5)) [67,68]:…”