Correlating the Electrochemical Activity of Nickel Cobaltite Oxide Nanoplate with Composition Regulation: From Macro-Level Assessment to Ultra-Micro Identification

Spinel nickel cobaltite oxide (NCO) nanostructures have gained significant interest in electrocatalysis and electroanalysis, and their characteristics are traditionally evaluated through macro-level assessments, which primarily reflect average activities. However, due to their heterogeneities such as composition, size, shape, and defects, elucidating the individual or local electrochemical reactivity of these nanostructures is very critical but considerably challenging. Here, we synthesized various nanoplate-structured NCOs by regulating the cobalt–nickel compositions, and the electrochemical reactivity of individual NCO nanoplates was independently investigated using scanning electrochemical cell microscopy (SECCM), with the catalytic reduction of H2O2 employed as a model reaction. The SECCM-linear scanning voltammetric (LSV) method was applied to track the electrochemical signals of individual NCOs within an ultra-micro confined area. In-situ measurement revealed the NCO-2 nanoplate, with a Co/Ni ratio of 2:1, exhibited superior electrochemical performance in H2O2 reduction. Density functional theory (DFT) calculations further demonstrated that the larger reaction energies and more negative d-band center of the surface metal active sites in NCO-2 nanoplate were responsible for its superior performance. This investigation establishes a correlation between the electrochemical behavior and the composition regulation of NCOs and provides a valuable framework for the rational design of advanced electrochemical sensing materials with high catalytic performance.