“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 that obtained using 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 requires only 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 density of 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 a new strategy and theoretical support for constructing efficient and stable industrial-scale water electrolysis catalytic electrodes.