Trifunctional Electrocatalysis on Dual-Doped Graphene Nanorings-Integrated Boxes for Efficient Water Splitting and Zn-Air Batteries

Despite the exciting achievements made in synthesis of monofunctional electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), or hydrogen evolution reaction (HER), it is challenging to develop trifunctional electrocatalysts for both ORR/OER/HER. Herein, N, O-codoped graphene nanorings-integrated boxes (denoted NOGB) are crafted via high-temperature pyrolysis and following acid etching of hybrid precursors containing polymers and Prussian blue analogue cubes. The electrochemical results signified that the resulting NOGB-800 (800 refers to pyrolysis temperature) is highly active for trifunctional electrocatalysis of ORR/OER/HER. This can be reasonably attributed to the advanced nanostructures (i.e., the hierarchically porous nanostructures on the hollow nanorings) and unique chemical compositions (i.e., N, O-codoped graphene). More attractively, the rechargeable Zn-air battery based on NOGB-800 displays maximum power density of 111.9 mW cm(-2) with small charge-discharge potential of 0.72 V and excellent stability of 30 h, comparable with the Pt/C+Ir/C counterpart. The NOGB-800 could also be utilized as bifunctional electrocatalysts for overall water splitting to yield current density of 10 mA cm(-2) at a voltage of 1.65 V, surpassing most reported electrocatalysts. Therefore, the NOGB-800 is a promising candidate instead of precious metal-based electrocatalysts for the efficient Zn-air battery and water splitting.