Alkaline Electrolyte and Fe Impurity Effects on the Performance and Active-Phase Structure of NiOOH Thin Films for OER Catalysis Applications

Abstract

The effects of varying alkaline electrolyte and electrolyte Fe levels on the performance and active-phase structure of NiOOH thin films for catalysis of the oxygen evolution reaction were studied. An electrolyte effect on catalytic performance was observed. Under purified conditions, current densities followed the trend Cs + > K + ≈ Na + ≈ Li + at current densities > 1 mA/cm 2 . Under Fe-saturated conditions, current densities followed the trend K + ≈ Na + > Cs + > Li + at all current densities. Voltammetry was coupled with Raman spectroscopy for studies in LiOH and CsOH. Raman spectra were fit to Gaussian functions and analyzed quantitatively based on mean peak positions. Both purified and Fe-saturated CsOH promoted slightly lower peak positions than purified and Fe-saturated LiOH, indicating that CsOH promoted a NiOOH active-phase structure with longer Ni–O bonds. Both Fe-saturated CsOH and LiOH promoted slightly lower Raman peak positions than purified CsOH and LiOH, but only for one of the two Raman peaks. These results indicate that Fe promoted an active-phase structure with slightly longer Ni–O bonds. This study shows that the catalytic performance and active-phase structure of NiOOH can be tuned by simply varying the alkaline electrolyte and electrolyte Fe levels.