Water Oxidation in Acidic Solutions: Beyond Noble Metals

Abstract

Water oxidation, a kinetically demanding half-reaction, plays a vital role in hydrogen production through electrochemical water-splitting. Thus, the development of efficient and stable oxygen evolution reaction electrocatalysts has become a central theme for basic research in the field of renewable energy. Substantial progress has been made in developing robust and inexpensive noble metal-free heterogeneous electrocatalysts for water oxidation operating under alkaline and neutral pH conditions. There is, however, a scarcity of active and stable electrocatalysts for acidic water oxidation, which is an ideal pH condition for high purity hydrogen production and offers several other technological advantages. Low performance and poor stability of existing water oxidation electrocatalysts based on non-noble metals are mainly attributed to the dissolution of respective elements in acidic solution. Considering these challenging aspects, we constructed the water oxidations catalysts based on thermodynamically and acid-stable oxides, which are incorporated with catalytically active species (transition metal-based water oxidation catalysts). Specifically, the highly-disordered mixed metal oxide, based on cobalt, iron, and lead, produced in situ exhibits excellent OER performance with unprecedented stability, through self-healing mechanism, under harsh operating conditions of pH 0 and temperature 80 °C. Importantly, the Cobalt-iron-lead oxide demonstrates the capability of operating at industrially relevant rates of 0.5 A cm-2 at low OER overpotentials of 0.7 V. These findings highlight the new strategy to design highly active and acid-stable, noble metal-free, OER electrocatalysts that can essentially operate indefinitely. Our most recent developments focused on replacement of lead with alternative, less toxic components. The presentation will also highlight these new systems, some of which demonstrate outstanding stability even without a self-healing mechanism.