Strontium Substituted SmNiO3: Novel Electrode Materials for Alkaline Water Electrolysis

Abstract

Sr-substituted SmNiO3 perovskite-type oxides have been investigated for their electrocatalytic properties towards oxygen evolution reaction (OER) in alkaline medium. Materials were obtained by using low temperature malic acid sol-gel route. To know the redox behaviour, electrocatalytic activity and thermodynamic parameters of oxides, cyclic voltammetry (CV) and anodic polarization curve (Tafel plot) were recorded in 1 M KOH at 25 ºC. X-ray diffraction (XRD) study indicates the formation of almost pure perovskite phase of the material. A pair of redox peaks was observed (anodic; Epa = 494±12 mV and corresponding cathodic; Epc = 360±4 mV) in the potential region 0.0-0.7 V prior to onset of OER. As observed in the case of La-based perovskite oxides, Sr-substitutions in the SmNiO3 also enhance the electrocatalytic properties of the material. However, Sm-based oxides showed least electrocatalytic activity as compared to La-based oxides. The estimated values of Tafel slope and reaction order indicate that each oxide electrode, except SmNiO3, follows similar mechanistic path towards OER. Standard entropy of activation (DS˚#), standard enthalpy of activation (DH˚#) and standard electrochemical energy of activation (DHel˚#) was determined by recording the anodic polarization curve in 1M KOH at different temperatures.