Role of cobalt precursors in the synthesis of Co₃O₄ hierarchical nanostructures toward the development of cobalt‐based functional electrocatalysts for bifunctional water splitting in alkaline and acidic media

Abstract

The precursors have significant influence on the catalytic activity of nonprecious electrocatalysts for effective water splitting. Herein, we report active electrocatalysts based on cobalt oxide (Co3O4) hierarchical nanostructures derived from four different precursors of cobalt (acetate, nitrate, chloride, and sulfate salts) using the low‐temperature aqueous chemical growth method. It has been found that the effect of precursor on the morphology of nanostructured material depends on the synthetic method. The Co3O4 nanostructures exhibited cubic phase derived from these four precursors. The Co3O4 nanostructures obtained from chloride precursor have demonstrated improved oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) compared to other precursors due relatively higher content of Co3O4 nanostructures at the surface of material. An overpotential of 400 mV versus reversible hydrogen electrode (RHE) at 10 mA cm−2 was observed for HER. The Co3O4 nanostructures derived from the chloride precursor have shown favorable reaction kinetics via 34 mV dec−1 value of the Tafel slope for HER reaction. The Co3O4 nanostructures derived from chloride precursor have also shown an excellent HER durability for 15 hr in alkaline media. Furthermore, the OER functional characterization was carried out onto Co3O4 nanostructures derived from chloride precursor exhibited 220 mV overpotential at 10 mA cm−2 and Tafel slope of 56 mV dec−1. Importantly, the reason behind the favorable catalytic activity of Co3O4 nanostructures derived from chloride precursor was linked to one order of magnitude smaller charge transfer resistance and higher amount of Co3O4 content at the surface of nanostructures than the Co3O4 nanostructures derived from other precursors. The performance of Co3O4 nanostructures derived from chloride precursor via the wet chemical method suggests that cobalt chloride precursor could be of great interest for the development of efficient, stable, nonprecious, and environmentally friendly electrocatalysts for the chemical energy conversion and storage devices.

Coherent Design of CoAl Layered Double Hydroxide-Derived Co3O4 Cubes as a Competent Electrocatalyst for Water Splitting and Urea Electrolysis

“…Structural modification can be accomplished through various techniques, including the introduction of heteroatoms, employing surface control reagents, inducing oxygen vacancies, and the adjustment of physical properties . Co 3 O 4 materials have been studied in diverse morphologies such as nanoflowers, nanowires, and nanorods and have been explored for electrochemical applications. ,− ,− Among these morphologies, Fang et al selectively enlarged the numerous oxygen positions on the surface of the Co 3 O 4 NWs using a defect engineering approach, resulting in the enrichment of electronically rich active sites and significant enhancement in urea oxidation . In the same way, Sreekanth et al investigated the electrocatalytic processes of hydrothermally assisted self-assembled Co 3 O 4 nanorods for urea electrolysis …”