Stainless steel made to rust: a robust water-splitting catalyst with benchmark characteristics

By Schafer, Helmut; Sadaf, Shamaila; Walder, Lorenz; Kuepper, Karsten; Dinklage, Stephan; Wollschlager, Joachim; Schneider, Lilli; Steinhart, Martin; Hardege, Jorg & Da
Published in Energy Environ. Sci. The Royal Society of Chemistry 2015

Abstract

The oxygen evolution reaction (OER) is known as the efficiency-limiting step for the electrochemical cleavage of water mainly due to the large overpotentials commonly used materials on the anode side cause. Since Ni-Fe oxides reduce overpotentials occurring in the OER dramatically they are regarded as anode materials of choice for the electrocatalytically driven water-splitting reaction. We herewith show that a straightforward surface modification carried out with AISI 304, a general purpose austenitic stainless steel, very likely, based upon a dissolution mechanism, to result in the formation of an ultra-thin layer consisting of Ni, Fe oxide with a purity >99%. The Ni enriched thin layer firmly attached to the steel substrate is responsible for the unusual highly efficient anodic conversion of water into oxygen as demonstrated by the low overpotential of 212 mV at 12 mA cm-2 current density in 1 M KOH, 269.2 mV at 10 mA cm-2 current density in 0.1 M KOH respectively. The Ni, Fe-oxide layer formed on the steel creates a stable outer sphere, and the surface oxidized steel samples proved to be inert against longer operating times (>150 ks) in alkaline medi

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