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.