Hierarchical Cobalt Borate/MXenes Hybrid with Extraordinary Electrocatalytic Performance in Oxygen Evolution Reaction

Graphical Pushing to the edge : Two-dimensional Ti 3 C 2 T x supported cobalt borate (Co-Bi) is a potential catalyst for oxygen evolution reaction in alkaline medium. The Co-B i /Ti 3 C 2 T x hybrid displays a hierarchical structure enabling improved exposure of active surface sites, mass diffusion, and charge-transfer characteristics. Consequently, the hybrid material can deliver a stable current density (10 mA cm −2 ) at a low overpotential (250 mV). Oxygen evolution reaction (OER) is a key reaction for many renewable energy storage and conversion techniques. Developing efficient non-precious metal-based electrocatalysts for OER has attracted increasing attention. Herein is reported a strategy to fabricate hierarchical cobalt borate/Ti 3 C 2 T x MXene (Co-B i /Ti 3 C 2 T x ) hybrid through fast chemical reactions at room temperature. This interesting hierarchical structure of Co-B i /Ti 3 C 2 T x hybrid is beneficial for exposing more active sites, improving mass diffusion, and charge-transfer pathways for electrochemical reaction. Moreover, a strong interaction between Co-B i and Ti 3 C 2 T x ensures efficient charge transfer and facilitates the electrostatic attraction of more anionic intermediates for a fast redox process. Consequently, the hierarchical Co-B i /Ti 3 C 2 T x hybrid shows extraordinary OER catalytic activity to deliver a current density of 10 mA cm −2 at an overpotential of 250 mV, and a Tafel slope of about 53 mV dec −1 .