Assembling Ni–Fe Layered Double Hydroxide 2D Thin Films for Oxygen Evolution Electrodes

Continuous hydrothermal flow synthesis (CHFS) of Ni–Fe layered double hydroxide (LDH) leads to waterborne dispersions of 2D nanoplatelets in the range of 10–50 nm in lateral size. Conversion of the as-synthesized LDH nanoplatelet dispersion into inkjet printing inks results in high precision patterning and complete substrate coverage with low LDH loadings in the range of μg cm–2. The Ni–Fe LDHs’ anisotropy induces a preferential in-plane alignment to a glassy carbon substrate producing low-porosity films. Thin Ni–Fe LDH films in the submicrometer range exhibit superior electrocatalytic activity for the oxygen evolution reaction (OER), with an overpotential of 270 mV at 10 mA cm–2 and a Tafel slope of 32 mV dec–1. The particle alignment creates a compact film and induces a loading-independent electrochemical performance of the Ni–Fe LDH electrodes for loadings above 50 μg cm–2. The combination of CHFS and inkjet printing represents a promising hyphenation of large-scale synthesis and electrode production.