4 - Oxygen evolution reaction (OER) at nanostructured metal oxide electrocatalysts in water electrolyzers

Abstract

The oxygen evolution reaction (OER) is of fundamental importance as a half-reaction in industrial electrochemical processes. The development of high-performance OER catalysts is a big issue in this field. Recently, the development of OER catalysts for water electrolysis has attracted great attention because of the increasing demand for the electrochemical production of hydrogen. In this chapter, nanostructured OER catalysts used at moderate temperature (mostly below 100°C) in acid and base electrolytes are summarized. In an acid electrolyte, precious metal-based oxides, such as iridium oxides and ruthenium oxides, are the main targets of nanostructured metal oxide catalysts. Nanostructural control is significant to improve their surface area and mass transport. In a basic electrolyte, transition metal-based oxides and hydroxides can be used as catalysts with high activity. NiFe-layered double hydroxides are regarded as one of the best OER catalysts in a basic electrolyte. Its exfoliation into nanosheets is an efficient way to increase its catalytic activity, though further nanostructural control is relatively limited. In conclusion, nanostructured catalysts exhibit high surface area, good mass transportation, and good electronic conduction. Some of nanostructures showed positive effects regarding their durability. However, because of the limited compositions of possible OER catalysts, types of nanostructures are rather limited. The development of novel synthetic techniques, which allow nanostructural control of the materials of synthetic difficulty, will be the key issues in the future OER catalysts.