Nanostructured Transition Metal Oxides as a Bifunctional Electrocatalyst for Water Splitting Reactions

Abstract

The electrochemical water splitting by using renewable electricity is being considered as a sustainable, clean, and considerable source of hydrogen fuel for future transportation and energy applications. However, the large-scale production of H2 via water splitting is restrained due to the lesser stability of these electrode materials, effective proceeding of HER step in acidic media, as well as lethargic kinetics and high overpotential values of complex four-electron transfer OER process. Thus, ongoing research is based on fabricating effective bifunctional electrocatalyst, which can lessen the overpotential for OER and HER. This study has been focused on developing efficient bifunctional electrocatalysts for water splitting reactions. The primary emphasis has been done on the preparation of perovskite materials and its composites with other transition metal oxides. The great flexibility in composition and crystal structure points them to the tuneable electronic structure of perovskite oxides. Herein, LSTN perovskite has been synthesized initially followed by its exsolution in a reduced environment. The composite of LSTN has been made with a NiMn-LDH, to develop a 3D hierarchical heterostructure LSTN@NiMnlayered double hydroxide (La0.4Sr0.4Ti0.9Ni0.1O3-δ @NiMn-LDH) supported on highly conductive nickel foam. Another way to improve the characteristic property of LSTN, both for HER and OER was proposed and a composite of LSTN has been prepared with MXene to improve the conductive path for ion transportation. Currently, research has been driven towards double perovskite due to the stable nature of non-stoichiometric perovskite that has a great impact on transition metal 3d ϭ*- antibonding (eg) orbital electron filling. Moreover, the catalysts have been characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, energydispersive x-ray spectroscopy (EDX), and Scanning electron microscopy (SEM). The results show that catalysts have been prepared successfully. The bifunctional activity of catalysts has been tested by calculating Tafel slope, overpotential, and mass activity. Among the prepared composites, LSTN@NiMn-LDH, LSTN/MXene 66.67%, and STPF-0.2 has shown the most proficient results with high stability and low resistance values.