A rational design of efficient trifunctional electrocatalysts derived from tailored Co2+-functionalized anionic metal-organic frameworks.

Strategies for developing efficient energy conversion and storage devices that have been optimized by designing electrode materials is a critical challenge for researchers. Herein, we report the design and synthesis of a series of Co@NC trifunctional electrocatalysts derived from rationally designed cobalt-added anion MOF precursors and preliminarily reveal the relationship between the precursor and corresponding efficient electrocatalysts. Benefiting from the special composition of Co2+-doped anion MOFs involving Co2+ chelates as the Co2+ sources, the resulting CoT@NC electrocatalyst possesses abundant Co/Co-Nx/Co-Ox and multiple active nitrogen sites that are evenly distributed. As expected, the rich variety of active species and hierarchical pore structures endow CoT@NC with excellent performances toward ORR, HER, and OER, including a high half-wave potential value of 0.86 V for ORR and low overpotential values for OER (350 mV) and HER (209 mV) at 10 mA cm-2 in an alkaline solution. Moreover, we assembled a conventional Zn-air battery with CoT@NC as the air-cathode catalyst, which exhibited excellent rechargeable performance and ultrahigh durability. Moreover, CoT@NC coated on Ni foam was used as both anode and cathode for the overall water-splitting process, which needed a bias voltage of 1.70 V to achieve a current density of 10 mA cm-2. This study sheds light on the design, fabrication, and regulation of highly active cobalt-based electrocatalysts with abundant active sites and tunable pore structures for electrocatalysis and other applications.