Influence of the crystalline phase on the electrocatalytic behaviour of Sm2−xSrxNiO4−δ (x = 0.4 to 1.0) Ruddlesden–Popper-based systems: a comparative study of bulk and thin electrocatalysts

Abstract

Herein, the influence of compositional engineering via active site alternation on catalytic behaviour has been studied for the Ruddlesden–Popper-based system Sm_2−xSr_xNiO_4−δ. A phase change from orthorhombic (x = 0.6) to tetragonal (x = 1.0) in bulk Sm_2−xSr_xNiO_4−δ is confirmed by Rietveld (XRD) analysis, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). To alter the active sites, we fabricated thin films for x = 0.6 and x = 1.0 using a pulsed laser deposition technique. The electrocatalytic behaviour has been studied in an environmentally friendly medium, i.e., a neutral medium (pH = 7), for both bulk and thin films, and parameters such as transient response, electrochemical reversibility and oxygen evolution reactivity are measured. The cyclic voltammetry curves suggest that electrochemical reversibility for thin films is governed by adsorption as opposed to the diffusion observed for bulk samples. Our investigation further suggests that moderate electroactivity can be achieved with an increase in active sites on miniaturization with the phase change.