Transformation of stainless steel 316 into a bifunctional water splitting electrocatalyst tolerant to polarity switching

Abstract

It is an ongoing challenge to develop bifunctional electrocatalysts that are highly active and able to operate in the harsh alkaline electrolyte used in commercial electrolysers. In addition, commercial units cannot be directly integrated with intermittent renewable energy sources due to rapid start up and shut down conditions which rapidly deteriorates the anode and cathode materials. Here, a very simple electrochemical conditioning approach followed by galvanic replacement with gold nanoparticles at a level of 0.5 at.% is demonstrated to transform stainless steel (AISI 316) into an electrocatalyst that facilitates overall water splitting while showing excellent tolerance to reverse polarity conditions. The electrocatalyst is not only very active for the OER with a low Tafel slope value of 29 mV dec−1, but also shows excellent performance for the HER where high current densities of 100 mA cm−2 can be achieved. In a two-cell configuration, current densities greater than 150mA cm−2 can be achieved for overall water splitting in 6 M NaOH at a cell voltage of only 2 V indicating potential commercial applicability. Additionally, the electrodes demonstrate high tolerance to reversing the polarity of the cell over prolonged periods of up to 216 h where equal performance is maintained.