  Porous electrodes were developed using laser powder bed fusion of Inconel 718
lattice structures and electrodeposition of a porous nickel catalytic layer.
Laser energy densities of ~83-333 J/m were used to fabricate ~500 um thick
electrodes made of body centered cubic unit cells of 200-500 um and strut
thicknesses of 100-200 um. Unit cells of 500 um and strut thickness of 200 um
were identified as optimum. Despite small changes in feature sizes by the
energy input, the porosity of >50% and pore size of ~100 um did not change. In
a subsequent step, we used nickel electrodeposition to create smaller scale
pores on the electrode. The electrochemical performance of the electrodes for
hydrogen/oxygen evolution reaction (HER/OER) was evaluated in a three-electrode
setup. For HER, a much larger maximum current density of ~ -372 mA/cm2 at a
less negative potential of ~-0.4 V vs RHE (potential against reversible
hydrogen electrode) was obtained in the nickel-coated samples, as compared to
-240 mA/cm2 at ~-0.6 V in the bare one, indicating superior performance of the
coated sample. Conversely, OER exhibited minor performance differences upon
application of the coating, indicating insignificant dependence of OER to
surface composition and available surface.
