Structurally robust P/S Co-deposited Ni–Fe catalysts enabling long-term seawater electrolysis at ampere-level currents

Seawater, as an abundant and sustainable source, presents an effective alternative for overcoming the cost associated with electrolyzers utilizing fresh water sources. Its inherent ionic conductivity helps efficient green hydrogen generation using seawater electrolysis. However, the presence of chloride ions leads to catalyst dissolution and poor durability, posing significant challenges to long-term operation. In addition, polyionic species such as phosphates and sulfates can influence electrolysis performance by tuning the surface charge distribution, thereby suppressing the chloride adsorption. Herein, we developed Fe, S, and P co-deposited Ni foam catalysts, NF(Fe,P) and NF(Fe,P,S), to strategically exploit the role of polyionic species in enhancing the catalytic stability. The catalysts achieved high current densities of 1.60 A cm^-2 and 1.44 A cm^-2 at overpotentials of 390 mV and 530 mV, respectively, for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In a two-electrode arrangement, the assembled NF(Fe,P)//NF(Fe,P,S) cell showed a very high durability for 3000 h under ampere-level current density. The post-reaction characterization and electrochemical analyses reveal that the incorporation of polyionic species promotes favorable kinetics and suppresses chloride-induced degradation, resulting in high performance and long-term durability.