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

Schäfer, Helmut; Sadaf, Shamaila; Walder, Lorenz; Kuepper, Karsten; Dinklage, Stephan; Wollschläger, Joachim; Schneider, Lilli; Steinhart, Martin; Hardege, Jörg; Daum, Diemo

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 medium. In addition Faradaic efficiency measurements performed through chronopotentiometry revealed a charge to oxygen conversion close to 100%, thus underpinning the conclusion that no “inner oxidation” based on further oxidation of the metal matrix below the oxide layer occurs. These key figures achieved with an almost unrivalled-inexpensive and unrivalled-accessible material, are among the best ever presented activity characteristics for the anodic water-splitting reaction at pH 13.

Citation

Schäfer, H., Sadaf, S., Walder, L., Kuepper, K., Dinklage, S., Wollschläger, J., …Daum, D. (2015). Stainless steel made to rust: a robust water-splitting catalyst with benchmark characteristics. Energy & environmental science, 8(9), 2685-2697. https://doi.org/10.1039/c5ee01601k

• Journal Article Type: Article
• Acceptance Date: Jun 9, 2015
• Online Publication Date: Jun 9, 2015
• Publication Date: Sep 1, 2015
• Deposit Date: Aug 17, 2015
• Publicly Available Date: Aug 17, 2015
• Journal: Energy and environmental science
• Print ISSN: 1754-5692
• Electronic ISSN: 1754-5706
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 8
• Issue: 9
• Pages: 2685-2697
• DOI: https://doi.org/10.1039/c5ee01601k
• Keywords: Stainless steel
• Public URL: https://hull-repository.worktribe.com/output/377693
• Publisher URL: http://pubs.rsc.org/en/content/articlelanding/2015/ee/c5ee01601k#!divAbstract
• Additional Information: : This document is Similarity Check deposited; : Supplementary Information; : The Royal Society of Chemistry has an exclusive publication licence for this journal; OPEN ACCESS: This article is freely available. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (CC BY 3.0); : Single-blind; : Received 22 May 2015; Accepted 9 June 2015; Accepted Manuscript published 9 June 2015; Advance Article published 12 June 2015; Version of Record published 26 August 2015