Effect of Co-substitution on the electrocatalytic properties of Ni1.5Fe1.5O4 for oxygen evolution in alkaline solutions

Abstract

Some ternary ferrites having composition CoxNi1.5-xFe1.5O4 (0.0 ≤ x ≤ 1.25) have been synthesized by NH4OH co-precipitation method at 11.5 pH. Materials, so obtained, were tested for their electrocatalytic properties towards oxygen evolution reaction (OER) in the form film on Ni-support in alkaline solution. The study showed that the electrocatalytic properties the material increased with partial substitution of Co for Ni in the base oxide (Ni1.5Fe1.5O4). The value being highest with 0.5 mol Co-substitution. At E = 850 mV vs Hg/HgO in 1M KOH at 25 ºC, the electrode showed apparent current density 206.2 mA cm-2, which is about 3 times higher than the base oxide. The Tafel slope values were ranged between 46-82 mV decade-1. A pair of redox peak, an anodic (EPa = 522±28 mV) and corresponding cathodic (EPc= 356±9 mV), was observed in the cyclic voltammetry (CV) study of the material. The thermodynamic parameters namely, standard apparent electrochemical enthalpy of activation ( ), standard enthalpy of activation ( ) and standard entropy of activation ( ) for the oxygen evolution reaction (OER) have also been determined by recording anodic polarization curve in 1M KOH. The value of was observed to be almost similar with each oxide electrode. The values were highly negative and ranged between ~ -165 and ~ -207 J deg-1 mol-1. Phase and morphology of materials have been investigated by using physical techniques X-ray diffraction, infrared spectroscopy (IR) and scanning electron microscope (SEM), respectively.

Egg-White Mediated Sol-Gel Synthesis of Cobalt Ferrites and Their Electrocatalytic Activity Towards Alkaline Water Electrolysis

“…Further, the activity of the oxide (Co0.5Fe2.5O4 ) has been found to higher than those obtained by hydrothermal [26] (j=18.7 mAcm -2 at E=750mV), NH4OH Sol-gel Auto combustion [27] (j=100 mAcm -2 at E=828mV), NH4OH-COP [29] (j=100 mAcm -2 at E=886mV), Egg-white sol-gel [31] (j=100 mAcm -2 at E=865mV) methods, which are recently reported in literature. However, most of the binary [18][19][20]28,30] and ternary [21][22][23][24][25]32] oxides obtained by coprecipitation and other sol-gel routes show better electrocatalytic activity than the oxides conveyed in the present study.…”

“…The literature shows that the spinel ferrites generally possess lower electrocatalytic activity for oxygen evolution [7] as compared to that of spinel cobaltites [8][9][10][11][12][13][14][15][16][17]. However, physicochemical and electrochemical properties of these ferrospinels can be improved by adopting low temperature routes such as sol-gel, co-precipitation, hydrothermal etc and partial substituting suitable metal ions in the spinel ferrite matrix [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. For instance, Singh et al used low temperature co-precipitation method [4] and synthesized binary [18][19][20] and ternary [21][22][23][24][25] ferrites and studied their electrocatalytic properties towards oxygen evolution reaction (OER) in alkaline slutions.…”

“…Very recently, we have prepared spinel ferrites [27][28][29][30][31][32] by using different low temperature synthetic routes and studied the effect of preparation methods and metal ion substitution on the electrocatalytic properties. By adopting the Maensiri et al [33] egg-white sol-gel route, we synthesized Ni-and Mnsubstituted [29,30] spinel ferrites towards alkaline water electrolysis.…”

Partially substituted La for Sm in Sm 0.8 Sr 0.2 NiO 3 : An efficient electrocatalyst towards alkaline water splitting

“…As the scan rate increased from 20-120 mVsec − 1 , the anodic peaks moved to the top and cathodic peaks to the bottom potential sides. The anodic as well as cathodic peaks on each side shifted as the scan rate increased implying that the redox process is quasi reversible [34][35][36][37][38]. With the anodic to cathodic peak current ratio surpassing one, it reveals an unmistakable sign of irreversibility in the redox process during the electrochemical reaction [39,40].…”

Low Temperature Synthesis and Characterization of NixFe3-xO4 (0≤x≤1.5) Electrodes for Oxygen Evolution Reaction in Alkaline Medium

“…Recently Singh et al [8,9,31,[33][34][35][36][37][38][39] used coprecipitation technique at controlled pH (= 11) for preparation of a series of binary and ternary ferrites by partially substituting iron atoms with different foreign metal ions in Fe3O4 matrix and found considerable enhancement in electrocatalytic activity towards OER. In the last few years, we [40][41][42][43] have also prepared cobalt, nickel and manganese substituted ferrites and found improvement in activity towards OER in substituted oxides. The Ni-substituted spinel ferrites [40] were synthesized by novel egg-white sol-gel method as reported by Maensiri et al [44].…”