Self-Supported 3 D Ultrathin Cobalt–Nickel–Boron Nanoflakes as an Efficient Electrocatalyst for the Oxygen Evolution Reaction

Graphical Flakes make O 2 : Self-supported ultrathin CoNiB nanoflakes are prepared by a simple one-step solid-state boronation. The unique sheet-like structure, bimetallic boride components, and optimal hybrid crystalline nature enable a synergistic promotion for the catalysis of the oxygen evolution reaction with long-term stability. The development of highly active and efficient nonprecious-metal electrocatalysts for the oxygen evolution reaction is important for the design of renewable energy production and storage devices. In this work, highly dense, ultrathin Co–Ni boride nanoflakes supported on a 3 D CoNi skeleton are fabricated in situ by a simple one-step, high-temperature, solid-state boronation process. As a result of the induced high electroactive surface area and low charge transfer resistance, CoNiB-700 exhibits high catalytic activity at an overpotential of 262 ( η 10 ) and 284 mV ( η 20 ) to deliver current densities of 10 and 20 mA cm −2 , respectively, with a Tafel slope of 58 mV dec −1 in an alkaline medium towards the oxygen evolution reaction. DFT calculations show that the Ni-regulated Co–B compound has a lower rate-determining energy barrier for the *OOH intermediate than the mono-Co–B compound, which facilitates the production of more active catalytic sites for an accelerated surface charge-transfer process for the oxygen evolution reaction.