High-performance hierarchical ultrathin sheet-based CoOOH hollow nanospheres with rich oxygen vacancies for the oxygen evolution reaction

Abstract

The oxygen evolution reaction (OER) is a key process in water splitting, rechargeable metal–air batteries and fuel cells, and the design of highly efficient, stable and non-noble metal-based electrocatalysts for the OER remains a great challenge so far. Here, we report the rational design and synthesis of hierarchical ultrathin nanosheet-based CoOOH hollow nanospheres with rich oxygen vacancies using a room-temperature self-template strategy with organic–inorganic hybrid Pi-Co-glycerate hollow nanospheres as the templates. The anions (H₂PO₂⁻) in the templates enable the proceeding of anion-exchange reaction at room temperature, and the resultant unique structural features (i.e., ultrathin thickness, rich oxygen vacancies and central void space) endow the CoOOH hollow nanospheres with excellent performance in the electrocatalytic OER. The obtained CoOOH hollow nanospheres exhibit a Tafel slope of 49 mV dec⁻¹ and a low overpotential of 275 mV at the current density of 10 mA cm⁻², superior to the γ-CoOOH nanosheets with an overpotential of 304 mV and the bare Ni foam with an overpotential of 362 mV at the same current density. Importantly, these CoOOH hollow nanospheres possess the lowest overpotential of 340 mV at the current density of 200 mA cm⁻² among the reported Co-based nanomaterials (370–770 mV). This research proposes a new chemical conversion mechanism and provides a new approach for the fabrication of hollow nanomaterials at room temperature, facilitating the development of efficient OER catalysts.