Electro-oxidation of a cobalt based steel in LiOH: a non-noble metal based electro-catalyst suitable for durable water-splitting in an acidic milieu

Abstract

The use of proton exchange membrane (PEM) electrolyzers is the method of choice for the conversion of solar energy when frequently occurring changes of the current load are an issue. However, this technique requires electrolytes with low pH. All oxygen evolving electrodes working durably and actively in acids contain IrOx. Due to their scarcity and high acquisition costs, noble elements like Pt, Ru and Ir need to be replaced by earth abundant elements. We have evaluated a cobalt containing steel for use as an oxygen-forming electrode in H2SO4. We found that the dissolving of ingredients out of the steel electrode at oxi-dative potential in sulfuric acid, which is a well-known, serious issue, can be substantially reduced when the steel is electro-oxidized in LiOH prior to electrocatalysis. Under optimized synthesis conditions a cobalt-containing tool steel was rendered into a durable oxygen evolution reaction (OER) electrocatalyst (weight loss: 39 µg mm −2 after 50 000 s of chronopotentiometry at pH 1) that exhibits overpotentials down to 574 mV at 10 mA cm −2 current density at pH 1. Focused ion beam SEM (FIB-SEM) was success-fully used to create a structure-stability relationship.

Free‐Sustaining Three‐Dimensional S235 Steel‐Based Porous Electrocatalyst for Highly Efficient and Durable Oxygen Evolution

“…substantially.T ot he besto fo ur knowledge, some of our group were the first to tailor steel intentionally into outstanding,e fficient, and stable OER electrocatalysts [56][57][58] on the basis of, inter alia, thin Ni, Fe oxide layers firmly attachedt ot he iron-based matrix. Benchmark OER properties were showna tp H13a nd pH 14, as the overpotential (h)a mounted to 212 mV at 12 mA cm À2 in 1 m KOH and to 269.2 mV at 10 mA cm À2 in 0.1 m KOH, respectively.V ery recently,h ydrothermal/electrochemicalo xidation of CrNi-based steel [59] as well as the surface oxidation of Ni42 [60] and X20CoCrWMo10-9//Co 3 O 4 steel [57,61] also provedt ob es uitable for the efficient preparation of acceptable OER catalysts that weres table and workedo ver a wide pH range. Besides surface oxidation, phosphorization and sulfurization have also been appliedt os teel, that is, Steel 316 (basically consisting of Ni, Cr,a nd Fe), to gain better overall OER characteristics.…”

Corrosion Behavior of SUS 304L Steel in pH 13 NaOH Solution

“…5(e) at 852.6 eV and 851.2 eV corresponds to a metallic Ni peak and a satellite peak, respectively. [31][32][33][34] From these results, it may be concluded that Cr and Fe formed an oxide film on the surface of the SUS 304L, and that Ni in the metallic state was present close to the surface.…”

“…5(c) indicates metallic Cr, and the peak near 576.6 eV that of Cr oxide. [31][32][33][34] The peak at 706.9 eV in Fig. 5(d) is corresponding to metallic Fe.…”

“…5(a) was resolved into three peaks at 285.0 eV, 286.5 eV, and 288.9 eV, as in previous reports. [31][32][33][34] In the result for O 1s in Fig. 5(b), two peaks resolution, at 529.9 and 532.2 eV, was performed.…”

“…The 529.9 eV peak in Fig. 5(b) is thought to represent the bond between oxygen and Cr, Fe, and Ni, and the peak at 532.2 eV can be assigned to the bond between oxygen and C. [31][32][33][34] It may be considered that the peak near 574.3 eV in Fig. 5(c) indicates metallic Cr, and the peak near 576.6 eV that of Cr oxide.…”