Framework for additive manufacturing of porous Inconel 718 for electrochemical applications

Abstract: 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.