Freestanding lamellar nanoporous Ni–Co–Mn alloy: a highly active and stable 3D bifunctional electrode for high-current–density water splitting

Retaining satisfactory electrocatalytic performance under high current density plays a crucial role in industrial water splitting but is still limited to the enormous energy loss because of insufficient exposure of active sites caused by the blocked mass/charge transportation at this condition. Herein, we present a freestanding lamellar nanoporous Ni–Co–Mn alloy electrode (Lnp-NCM) designed by a refined variant of the “dealloying-coarsening-dealloying” protocol for highly efficient bifunctional electrocatalyst, where large porous channels distribute on the surface and small porous channels at the interlayer. With its 3D lamellar architecture regulating, the electrocatalytic properties of the electrodes with different distances between lamellas are compared, and faster energy conversion kinetics is achieved with efficient bubble transport channels and abundant electroactive sites. Note that the optimized sample (Lnp-NCM4) is expected to be a potential bifunctional electrocatalyst with low overpotentials of 258 and 439 mV at high current densities of 1000 and 900 mA·cm⁻² for hydrogen and oxygen evolution reactions (HER and OER), respectively. During overall water splitting in a two-electrode cell with Lnp-NCM4 as cathode and anode, it only needs an ultralow cell voltage of 1.75 V to produce 100 mA·cm⁻² with remarkable long-term stability over 50 h. This study on lamellar nanoporous electrode design approaches industrial water splitting requirements and paves a way for developing other catalytic systems.

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