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

摘要

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