Oxygen evolution on La1-xSrxCoO3 Pellet-Electrodes in alkaline Solution: Charge Carrier density dependence of electrocatalytic activity

Abstract

Alkaline water electrolysis need a catalyst with low overpotential and high current densitiy for oxygen evolution in order to be a commercial viable hydrogen source in the future. Finding and establishing a correlation between electrocatalytic activity and charge carrier density will help towards finding an optimum catalyst for this purpose. Such comparisons have been made using theoretical values for charge carrier density, but the aim of this work is to use charge carrier data from experimental values.Five powders of La1-xSrxCoO3 (with compositions x = 0, 0.25, 0.5, 0.75, 1) were synthesized by solid-state synthesis and sintered to pellets. The pellet surfaces were investigated in alkaline solution (pH = 13) by cyclic voltammetry, polarization and impedance measurements. Polariza- tion curves with Tafel lines and Mott-Schottky plots were established. The powders and pellet surfaces were investigated by XRD, SEM, EDS, AFM and light microscope.The polarization curves revealed a volcanic behavior with an increase in catalytic activity from x = 0 up to x = 0.75 and then decreasing. The charge carrier density increased with increasing strontium doping. The resulting comparison gave figure 34. Surface investigation revealed much porosity. Because of corrosion, the surface area increased with measuring, and finding the real surface area and the roughness proved to be problematic.A volcanic behavior of the charge carrier density and electrocatalytic activity relationship were observed. Finding roughness factor values by measuring double layer capacitance measured by the cyclic voltammetry method and dividing by the nominal capacitance for a flat surface proved to be unsuccessful. Better synthesis and sintering procedures of pellets are needed to increase the density of the samples in order to decrease the roughness and the effect of corrosion.