"Rock-solid" CoB-based sponge electrodes for overall seawater splitting at industrial-level current density

Abstract

Developing highly stable and economical non-precious metal catalytic electrodes is the core issue in solving the current problem of seawater electrolysis at industrial-scale current densities. In this work, a dense layer of Cobalt-boron (CoB) nanospheres was in-situ grown on the surface of hydrophilic polyurethane sponge (HPS) via a mild electroless plating method, constructing a high-activity, high-strength, self-supporting bifunctional CoB@HPS electrode compared with the nickel foam substrate (NF). Based on its high specific surface area, abundant active sites, and porous hydrophilic structure, the HPS with the grown nano-spherical CoB exhibits significant electrochemical catalytic efficiency. Meanwhile, an efficient synergistic catalytic mechanism is established between the Co(OH)2/CoOOH species and CoB. In the hydrogen evolution/oxygen evolution reaction (HER/OER) processes, overpotentials of only 19 and 199 mV are required to reach 10 mA cm-². This electrode only needs a voltage of 1.60 V to promote overall water splitting (OWS) at a current density of 100 mA cm-², and it can continuously operate for more than 600 h at an industrial-scale current of density 500 mA cm-² without significant performance degradation. More attractively, this strategy has broad applicability in industry, enabling multi-element doping (iron/nickel/phosphorus), flexible substrate usage (nickel foam NF/hydrophilic cloth CC/hydrophobic asbestos HA/polyurethane plastic PU), and large-area construction (5.0 cm × 5.0 cm). This work provides new strategy and theoretical support for constructing efficient and stable industrial-scale water electrolysis catalytic electrodes.