Electrochemically activated self-supported 2D bilayer hierarchical porous hydroxide electrodes for rapid OH− storage

A hierarchical porous 2D bilayer nickel‑cobalt hydroxide (NCBTC@NCH-ECA) is in situ fabricated on a nickel foam substrate using an electrochemical activation (ECA) pore-forming strategy. The applied external potential activates the outer-layer hydroxide and enables the successful transformation of NCBTC by driving the periodic dissociation of its coordination bonds via OH − . Coupled with the deposition and dissolution of nickel‑cobalt hydroxide under high potential, it endows the NCBTC@NCH-ECA composite with abundant hierarchical porous structures and enhanced electrical conductivity. The optimized NCBTC@NCH-ECA electrode shows an areal capacitance of 17.9 F cm −2 at 2 mA cm −2 and demonstrates improved cycling stability retaining 69.0 % after 5000 cycles. The NCBTC@NCH-ECA//AC presents a power density of 40.0 mW cm −2 and an energy density of 0.4 mWh cm −2 , which demonstrate excellent application value. The superior electrochemical performance of NCBTC@NCH-ECA composite should contribute to its hierarchical pore network, two-dimensional layered structure, the enhanced wettability and improved OH − transfer collectively. This work provides a feasible strategy for optimizing the electrochemical performance of thick electrodes. • NCBTC@NCH-ECA with well-tailored micropores is in-situ fabricated by electrochemical activation. • The sample demonstrates a superior areal capacitance and high mechanical reliability. • The well-matched micropores favors for the faster OH − storage. • The tightly-bound 2D bilayer provides a stable support and rich interface features.