Development of CGO/LSF N-P Type Heterostructure as A Bi-Functional Electrocatalyst for Alkaline Water-Splitting at Room Temperature

Abstract

The n-type gadolinium-doped cerium oxide (Ce1-xGdxO2-∂; CGO) and p-type strontium-doped lanthanum ferrite (La1-xSrxFeO3-∂; LSF) ceramics are well-known for electrocatalytic applications at high-temperature. The doping-induced defects and local redox moieties (Ce3+/4+ and Fe2+/3+) results in catalytic properties of CGO and LSF material. This work focuses on the synthesis and characterization of nanocatalysts taking CGO and LSF in different weight ratios i.e., 50:50 (CL55), 70:30 (CL73) and 90:10 (CL91) by one-pot one-step sol-gel auto-combustion process. Individual CGO and LSF were also synthesized for comparison purposes. Doping concentration of Gd3+ and Sr2+ in CGO and LSF were typically set to 10 and 40 mole% respectively. All the nanocatalysts were characterized with XRD, SEM, XPS and BET surface area. The oxygen and hydrogen evolution reaction (OER and HER) kinetics were studied in 1M KOH electrolyte. Linear sweep voltammetry, cyclic voltammetry and Impedance Spectroscopy were used to study the electrochemical water-splitting behavior. Incorporation of 10 wt% LSF significantly enhanced the bifunctionality (OER and HER) of the composite CL91. Nonetheless a remarkable improvement of current density (benchmark 10mA/cm2) has been registered for CL91 with very low Tafel slope (86 mV/dec) for HER. Lastly a stability test was performed with the CL91 for 14 hours by choronopotentiometry method.