Conductivity Modulation of 3D-Printed Shellular Electrodes through Embedding Nanocrystalline Intermetallics into Amorphous Matrix for Ultrahigh-Current Oxygen Evolution

Scaling up commercial hydrogen production by water electrolysis requires efficient oxygen evolution reaction (OER) electrodes that can deliver large current densities (more than 500 mA cm⁻²) at low overpotentials. Here, a highly active and conductive shell-based cellular (Shellular) electrode is developed through a strategy of embedding nanocrystalline Ni₃Nb intermetallics into an amorphous NiFe-OOH matrix. The tailor-made laser remelting process enables the dispersive precipitation of corrosion-resistant nanocrystalline Ni₃Nb in large numbers. After in situ electrochemical activation in the self-developed growth-mode-control electrolyte, the amorphous NiFe-OOH nanosheets and nanocrystalline Ni₃Nb are formed on the as-printed Inconel 718. The conductive atomic force microscopy (C-AFM) studies and density functional theory (DFT) calculations elucidate that nanocrystalline Ni₃Nb can simultaneously enhance the conductivity and activity of the catalyst film. Additionally, a Shellular structure inspired by nature is designed, interestingly, its specific surface area keeps constant with increases in porosity. This design can result in a large surface area and high porosity but with less material cost. Using this electrochemically activated Shellular electrode for OER, a high current density of 1500 mA cm⁻² is achieved at a record-low overpotential of 261 mV with good durability. This development may open the door for large-scale industrial water electrolysis.