Designing Superhydrophilic Hydrogels as Binder-Free Catalysts for Enhanced Oxygen Evolution Performance

Water electrolysis is an environmentally friendly and sustainable hydrogen production method. The proper design of the catalyst surface is essential for the oxygen evolution reaction (OER) in the water electrolysis process because the catalytic effect is highly dependent on contact surface properties such as the homogeneity of the coating and the stability of the catalyst, as well as the wettability of the electrolyte. Herein, hydrogel [consisting of poly(vinyl alcohol) (PVA) cross-linked with quaternized chitosan (HACC)] loaded on nickel foam (NF) was chosen to study the OER properties of iron (Fe) in organic molecules. Owing to the unique hydrophilicity, uniformity, and stability of hydrogel, the superhydrophilic Fe-HACC-PVA/NF exhibits a low overpotential of 225 mV versus reversible hydrogen electrode at 10 mA cm–2 and shows favorable stability (only 2.3% loss of current density after 24 h at 100 mA cm–2), which outperforms most Fe-based transition-metal OER catalysts. This work demonstrates that introducing a superhydrophilic catalyst surface structure to dissociate the adsorbed water is a productive strategy to enhance the performance of OER. Furthermore, the rational design of hydrophilic interface materials in this work provides a facile method to developing OER catalysts.