Improved trifunctional electrocatalytic performance of integrated Co3O4 spinel oxide morphologies with abundant oxygen vacancies for oxygen reduction and water-splitting reactions

A simple and surfactant-free hydrothermal method was used to produce different forms of integrated nanostructures of Co 3 O 4 spinel oxides, which exhibited excellent trifunctional electrocatalytic activity toward oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The surface morphology and structural features of Co 3 O 4 spinel oxide catalysts were investigated, and 40–70-nm nanocube particles were found decorated over petal-, slab-, and flower-like spinel oxide structures with the dominant (111) crystalline plane. According to physicochemical studies, the Co 3 O 4 spinel oxide catalyst with the slab morphology has a high Co 3+ /Co 2+ ratio and an abundance of oxygen vacancies, resulting in improved trifunctional performance with an early ORR onset potential (0.91 V), low overpotential for OER (460 mV) and HER (363 mV), and extended durability. This study provides insights into the design and structural features of Co 3 O 4 spinel oxides through a simple and template-free synthesis approach to compete as an efficient trifunctional electrocatalyst for water splitting and metal–air battery applications. • Co 3 O 4 nanocubes on different structures prepared by one-step hydrothermal method. • Integrated Co 3 O 4 spinel oxides with abundant oxygen defects for electrochemical reactions. • Electronic properties and Co 3+ /Co 2+ ratio play crucial role on tri-functional electrocatalytic activity. • Co 3 O 4 NCs@NSs exhibit good activity and durability for ORR, OER and HER.