CoFePBA Nanosheets on Carbon Nanotubes Coupled with Nickel-Encapsulated Carbon Tubules for Efficient and Highly Stable Overall Seawater Electrolysis

The generation of H2 by seawater electrolysis is limited by anodic chlorine corrosion and sluggish cathodic hydrogen evolution reaction (HER). Here, we report a simple approach for developing cobalt iron (CoFe)-based Prussian blue analogue with a nitrogen-doped carbon nanotube composite (CoFePBA/NCNT) and nickel-encapsulated carbon tubules (Ni/NCT) as oxygen evolution reaction (OER) and HER catalysts for overall seawater electrolysis utilizing graphite felt or carbon paper as the catalyst substrate, thus avoiding chlorine corrosion of the metal substrate. Instead of a commonly known hydrothermal method, a simple brush coating method was employed for catalyst coating which is feasible for large-scale electrolyzer fabrication. Our developed electrolyzer has shown a low overall seawater splitting voltage of 1.71 V and a good stability of 50 h in seawater with excellent selectivity for OER over hypochlorite formation at room temperature (26 °C). High OER activity is attributed to abundant catalytic sites provided by interconnected CoFePBA nanosheets and high intrinsic catalytic activity. Moreover, suppressed hypochlorite formation and corrosion resistance resulting from the synergistic effect of CoFePBA and NCNT make CoFePBA/NCNT||Ni/NCT a potential candidate for seawater electrolyzers. Our work paves a way to demonstrate seawater electrolyzer performance with nonprecious catalysts on a nonmetallic support.