Framework for additive manufacturing of porous Inconel 718 for electrochemical applications

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 $\mu$m thick electrodes made of body centered cubic unit cells of 200-500 $\mu$m and strut thicknesses of 100-200 um. Unit cells of 500 $\mu$m and strut thickness of 200 $\mu$m were identified as optimum. Despite small changes in feature sizes by the energy input, the porosity of more than 50 percent and pore size of 100 $\mu$m did not change. Nickel electrodeposition created a network of submicrometer pores. The electrodes' electrochemical efficiency was assessed by analysing hydrogen/oxygen evolution reaction (HER/OER) in a three-electrode setup. For HER, a much larger maximum current density of -372 mA/cm$^2$ at a less negative potential of -0.4 V vs RHE (potential against reversible hydrogen electrode) was produced in the nickel-coated samples, as compared to -240 mA/cm$^2$ at -0.6 V in the bare one, indicating superior performance of the coated sample. For OER, however, both bare and nickel-coated electrodes similarly showed a maximum current density of 350 mA/cm$^2$ at 1.8 V vs RHE due to performance trade-offs arising from sample composition and structure.