Interface engineering and oxygen vacancy of hollow/porous Co-CoO heterojunction nanoframes for high-activity electrocatalysis overall water splitting

Cobalt-based oxides are regarded as promising electrocatalysts in the field of overall water splitting ascribed to superior activity and desirable stability. Nevertheless, the poor electrical conductivity and insufficient active centers limit their development seriously. Herein, the hollow/porous Co-CoO nanoframes (denoted as Co-CoO NFs) with heterojunction and abundant oxygen vacancies have been constructed via continuous calcination and in-situ reduction strategies. Furthermore, the influence of heterostructure and oxygen vacancy on electrocatalytic activity is investigated systematically. The heterojunction interface formed by Co and CoO could expose more active sites and accelerate charge transfer. Besides, oxygen vacancy could regulate electronic structure, lowering the intermediate binding energy and reducing charge transfer impedance. Furthermore, the hollow/porous structure could increase the accessible internal and external surface area. As a result, Co-CoO-400 NFs exhibit prominent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) behavior, achieving the current density of -10 mA cm-2 and 10 mA cm-2 with the low overpotential of 103.0 and 276.0 mV, respectively, and the voltage required for overall water splitting is 1.54 V, surpassing the most reported Co-based electrocatalysts recently. Overall, this work provides an intellection and vision for designing dual-function electrocatalysts with controllable morphology, low energy consumption, and high activity, making a significant contribution for solving the future energy crisis.