Fabrication of Co, N-codoped carbon on carbon paper as a binder-free electrode for alkaline seawater electrolysis at high current densities

Abstract

Due to the abundance of seawater resources, alkaline seawater electrolysis is a very attractive and sustainable way to produce hydrogen. However, the corrosion of electrodes, the shedding of catalysts and the collapse of electrode frameworks caused by chloride ions are still the main challenges for the long-term operation of electrolyzers at industrial-scale current densities. In this work, we reported a self-supporting cobalt and nitrogen-codoped carbon electrode derived from a ZIF-67/melamine–polyethyleneimine/carbon fiber paper (CP) composite, in which the uniformly distributed Co–N configurations were introduced into a continuous adhesive-free carbon skeleton by adjusting the annealing process. For hydrogen evolution in alkaline seawater of pH 14, the ZIF/MP/CP-800 electrode achieved a current density of 500 mA cm⁻² at a low overpotential of 0.561 V and maintained stable operation at 400 mA cm⁻² for 12 000 min. Moreover, it operated continuously for more than 800 min at a current density of 50 mA cm⁻² in seawater at pH 10. Its excellent catalytic activity and stability stem from the synergistic effect between the Co–N active sites and the strong self-supporting structure, which facilitates efficient charge transfer and inhibits metal dissolution due to chlorine corrosion. This work provides a feasible strategy for designing durable self-supporting electrodes and promotes the practical application of alkaline seawater electrolysis technology in industrial-scale hydrogen production.