Improved HER activity of Ni and stainless steel electrodes activated by NiCoMo ionic activator - A combined DFT and experimental study

In this paper we discussed various factors contributing to the improvement of hydrogen evolution reaction (HER) activity of Ni and stainless steel electrodes activated by in situ addition of NiCoMo activators, using a combination of experimental techniques and DFT calculations. By comparing energy consumption of stainless steel (SS) electrodes in a lab scale alkaline electrolyzer with and without ionic activation, we obtained reduction of energy consumption by 21% at industrial conditions (high current density and temperature). We recorded U-I curves for activated and non-activated stainless steel electrodes in the current density range from 40 to 500 mA cm2 and in the temperature range 298-343 K, and the obtained results were used in an electrochemical model of the laboratory alkaline electrolyzer. Increase of the electrode surface upon addition of ionic activators was confirmed by profilometric measurements and SEM analysis. Finally, we applied density functional theory (DFT) to discuss partial roles of applied ionic activators (Ni, Co and Mo) in the modification and improvement of the intrinsic properties of the cathode towards the HER in alkaline medium. From the combination of profilometric, SEM and DFT results, we conclude that the main factor contributing to the improvement of HER activity of Ni electrodes upon NiCoMo activation is the increase of electrode surface area.